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  • 1.
    Burks, Terrance
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Akthar, F.
    Saleemi, M.
    Avila, M.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)2015In: Journal of Environmental and Public health, ISSN 1687-9805, E-ISSN 1687-9813, Vol. 2015, article id 687094Article in journal (Refereed)
    Abstract [en]

    Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water.The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developedarchitecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-Llactidenanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solutionunder a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps.Theadsorption of Cr(VI) speciesin solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofibernanocomposite.Theadsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnOand Cr(VI) ions as a function of pH.The adsorption and desorption experiments utilizing the ZnO-PLLAnanofiber nanocompositehave appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species.

  • 2.
    Bursell, Martin
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Pirjamali, M.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    La0.6Ca0.4CoO3, La0.1Ca0.9MnO3 and LaNiO3 as bifunctional oxygen electrodes2002In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, no 10, p. 1651-1660Article in journal (Refereed)
    Abstract [en]

    A series of perovskite catalysts was investigated for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte and at room temperature, supplied by oxygen or air. A meniscus cell was used to screen-test candidate catalysts for their bifunctionality and assess their activity for ORR at 3 mm depth of immersion (DOI) in the electrolyte. Based on the meniscus data LaNiO3, La0.1Ca0.9MnO3 and La0.6Ca0.4CoO3 were selected for further assessment in microelectrode and half-cell studies. Activity tests for the ORR and OER, Tafel slopes at high current densities and apparent activation energies for the ORR were determined using a microelectrode technique on samples of the selected perovskites, La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3 with and without graphite support. Tafel slopes of ca. 120 mV per decade and apparent activation energies of approximately 18 kcal mol(-1) were measured at high cathodic current densities. Cycle-life and performance of La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3-based gas-diffusion electrodes in half-cell configurations were tested at a constant current density of 25 mA cm(-2) With subsequent and intermittent polarizations. Similar activities resulted in the ORR, while increased numbers of cycles were observed for the La0.1Ca0.9MnO3-based electrode. Furthermore, electrode material compositions, especially PTFE contents were optimized to conform to the establishment of the three phase interactions of the electrode structure, Transmission Electron microscopy (TEM) and BET-surface area analyses were carried out in order to find out the morphological and surface properties of the perovskite materials.

  • 3.
    Caetano de Souza, Antonio Carlos
    et al.
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Silveira, José Luz
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Zanzi Vigouroux, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    A low cost & safe system of hydrogen production utilizing NaBH4 and CoO catalysis2007In: 2nd International Congress University-Industry Cooperation (UNIDU07), 2007Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to evaluate the hydrogen production through hydrolysisof sodium borohydride (NaBH4) utilizing catalysts containing CoO. The reactant is safe and stable(when dry) at room temperature. Few works and studies have presented results of investigationsutilizing catalysts containing cobalt; however utilizing catalysts containing CoO were not found yet.In this work simple and cheap hydrogen generation system was developed having reactions atnormal conditions of temperature and pressure. A solution containing a gravimetric composition of10% wt. NaOH, 10% wt. NaBH4 and 80% wt. H2O was utilized. The reaction was carried out atvarious times using the same catalyst to evaluate its performance. This catalyst presented highrates of hydrogen production, especially at its start-up (about 99% of the theoretical hydrogenvolume was produced) at room temperature. After start-up, e.g., when more solution was put, rateof hydrogen production decreased having its production performance also decreased. Probablythis fact occurred due to the formation of the solid phase products such as NaBO2 which might fillthe porous catalyst structure; decreasing the catalytic area. This catalyst is suggested in situationswhere high production rates are necessary such as start-up of fuel cells.

  • 4.
    Caetano de Souza, Antonio Carlos
    et al.
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Silveira, José Luz
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Zanzi Vigouroux, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hydrogen production through hydrolysis of NaBH4: The use of catalysts containing Pt and Pt-Ru2007In: 2nd International Congress University-Industry Cooperation (UNIDU07), 2007Conference paper (Refereed)
    Abstract [en]

    Several works about hydrolysis of NaBH4 utilizing various catalysts (such as catalysts containing Pt or Ru) are available in the literature. Investigations involving NaBH4 has increased due to the possibility to produce hydrogen using simple and safe systems, even at room temperatures with very high efficiencies. A solution containing a gravimetric  composition of 10%wt. NaOH, 10%wt. NaBH4 and 80%wt. H2O was utilized and the reaction was initiated immediately as soon as this solution was put in the chosen catalysts, in this case, catalysts containing Pt and mixtures of Pt-Ru. Catalysts containing Pt and Pt-Ru presented high yields of hydrogen after the solution being inserted in the reaction vessel several times. In this study it was found out that the rates of hydrogen production were increased with catalysts containing Pt and Pt-Ru (99 and 96% of theoretical hydrogen production respectively). The catalysts containing Pt presented higher production rate, while the catalysts containing the mixed Pt-Ru presented a quasi-linear production, e.g., stable production rate.

  • 5. Dong, Hanwu
    et al.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Noreus, Dag
    An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode2010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 9, p. 4336-4341Article in journal (Refereed)
    Abstract [en]

    Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

  • 6.
    Endalew, Abebe K.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Zanzi, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Heterogeneous catalysis for biodiesel production from Jatropha curcas oil (JCO)2011In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 36, no 5, p. 2693-2700Article in journal (Refereed)
    Abstract [en]

    This work focuses on the development of heterogeneous catalysts for biodiesel production from high free fatty acid (FFA) containing Jatropha curcas oil (KO). Solid base and acid catalysts were prepared and tested for transesterification in a batch reactor under mild reaction conditions. Mixtures of solid base and acid catalysts were also tested for single-step simultaneous esterification and transesterification. More soap formation was found to be the main problem for calcium oxide (CaO) and lithium doped calcium oxide (Li-CaO) catalysts during the reaction of jatropha oil and methanol than for the rapeseed oil (RSO). CaO with Li doping showed increased conversion to biodiesel than bare CaO as a catalyst. La(2)O(3)/ZnO, La(2)O(3)/Al(2)O(3) and La(0.1)Ca(0.9)MnO(3) catalysts were also tested and among them La(2)O(3)-ZnO showed higher activity. Mixture of solid base catalysts (CaO and Li-CaO)and solid acid catalyst (Fe(2)(SO(4))(3)) were found to give complete conversion to biodiesel in a single-step simultaneous esterification and transesterification process. (C) 2011 Elsevier Ltd. All rights reserved.

  • 7.
    Endalew, Abebe K.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Zanzi, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Inorganic heterogeneous catalysts for biodiesel production from vegetable oils2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 9, p. 3787-3809Article, review/survey (Refereed)
    Abstract [en]

    Biofuels are renewable solutions to replace the ever dwindling energy reserves and environmentally pollutant fossil liquid fuels when they are produced from low cost sustainable feedstocks. Biodiesel is mainly produced from vegetable oils or animal fats by the method of transesterification reaction using catalysts. Homogeneous catalysts are conventionally used for biodiesel production. Unfortunately, homogeneous catalysts are associated with problems which might increase the cost of production due to separation steps and emission of waste water. Inorganic heterogeneous catalysts are potentially low cost and can solve many of the problems encountered in homogeneous catalysts. Many solid acid and base inorganic catalysts have been studied for the transesterification of various vegetables oils. The work of many researchers on the development of active, tolerant to water and free fatty acids (FFA), as well as stable inorganic catalysts for biodiesel production from vegetable oils are reviewed and discussed.

  • 8.
    Eriksson, Tore
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Temperature swing adsorption device for oxygen-enriched air2014In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 76, p. 174-179Article in journal (Refereed)
    Abstract [en]

    In connection with a project aimed at producing oxygen-enriched air from ambient air using temperature differences in the so-called temperature swing adsorption (TSA), a device was designed and constructed that took into consideration most of the conceivable parameters governing such a process. While designing the device, care was taken so that it was adaptable to different operating modes, fulfilling high versatility and extending to more processes than producing oxygen-enriched air. The device was small-scale, mounted on a movable table. It was equipped with a total of 54 individually controllable on/off valves. The valves could be controlled at a resolution of 1 s using a programmable logic controller, controlled by a personal computer, so the time program for the valves could be easily exchanged for a readymade program. The device had six cylinders, with removable lids filled with zeolite and easily maintained plastic tubing, which could therefore be changed or replaced without much difficulty. The results show that 15 L of oxygen could be produced at a concentration of 30% in the oxygen-enriched air per kg zeolite and hour. Equipping the device in the future with valves that close and open securely in both directions would vastly extend the possibility of using this technology to other applications, in addition to this method of TSA process for air separation.

  • 9. Hu, W. K.
    et al.
    Gao, X. P.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Middelman, E.
    Noreus, D.
    Zr-based AB(2)-type hydrogen storage alloys as dual catalysts of gas-diffusion electrodes in an alkaline fuel cell2004In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, no 26, p. 8756-8758Article in journal (Refereed)
    Abstract [en]

    Zr-based AB(2)-type hydrogen storage alloys as dual catalysts for hydrogen adsorption and oxidation reactions in alkaline fuel cells were investigated. A hydrogen-diffusion electrode composed of this hydride alloy was constructed, and its performance in terms of catalytic activities and durability was evaluated. Results demonstrated that the hydrogen-diffusion electrode had not only good activity but also excellent stability at a current density of 40-60 mA/cm(2) after surface treatments using a 1.0 M HF solution. XPS analyses showed that the improvement in catalytic activity is related to the formation of a nickel-rich layer and the removal of other oxides on the catalyst surface. The novel possible application of Zr-based hydride alloys could lead to an attempt to exploit new catalysts to lower material cost for hydrogen fuel cells.

  • 10. Hu, W. K.
    et al.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Noreus, D.
    AB(5)-type hydrogen storage alloys as catalysts in hydrogen-diffusion electrodes for novel H-2/hydride//perovskite/O-2 alkaline fuel cells2004In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, no 48, p. 18530-18534Article in journal (Refereed)
    Abstract [en]

    Development of a non-noble-metal catalyst electrode is an important issue in the research and development of fuel cells. The catalytic activity and durability of AB(5)-type hydrogen storage alloys used in hydrogen-diffusion electrodes for alkaline fuel cells are evaluated. The experiments demonstrate that the activity and stability for hydrogen oxidation is greatly improved if the particle size is decreased from 5-30 to 1-10 mum. This also improves the electrode stability. SEM and XRD analyses show that no disintegration of the smaller catalyst particles is observed in long-term tests. A novel H-2/hydride//perovskite/O-2 alkaline fuel cell was constructed as a non-noble-metal fuel cell concept. The results showed that both gas-diffusion electrodes had high catalytic activities and good stability. A maximum power density of 54 mW/cm(2) was achieved at 120 mA/cm(2) when using H-2/O-2 and 49 mW/cm(2) at 100 mA/cm(2) when using H-2/air.

  • 11. Jukka-Pekka, Spets
    et al.
    Petri, Kanninen
    Tanja, Kallio
    Jorma, Selkainaho
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Kari, Saari
    Martti, Larmi
    Towards an Efficient Direct Glucose Anion Exchange Membrane Fuel Cell System with Several Electro-Oxidation Units2017In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 12, no 5, p. 3697-3708Article in journal (Refereed)
    Abstract [en]

    This work covers the direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutralstate electrolyte of 0.1 M [PO4] (tot) having two high-performing anode electrocatalysts (Pt and PtNi) at 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was a Pt supported on carbon (60 wt.%). The PtNi/C had a total metal content of 40 wt.% and the Pt/C 60 wt.%. The operation of the AEMFC was controlled by means of an in-house made electronic load with PI-controller (i.e. a feedback controller, which has proportional and integral action on control error signal). There were two primary objectives with this study. At first, to find out how the electrode modifications of the anode (i.e. by increasing the thicknesses of these electrodes by adding extra carbon) affect the Coulombic efficiency (CE, based on the exchange of two electrons) and the specific energy (SPE, Wh kg(-1)) values of the direct glucose AEMFC. Secondly, investigate how a two-stage fuel cell system with two fuel cells concatenated and used one after the other for the electrochemical oxidation of glucose, influence the CE and SPE values. The results show that the modified PtNi anode shows superior results for the AEMFC compared to our earlier results. As for the two-stage fuel cell system, it increased the average electric power (mWh) and SPE when compared to single fuel cell systems except when the higher selective anode catalyst (Pt) was used in the first fuel cell prior to the fuel cell in the second fuel cell containing the lower selective anode catalyst (PtNi).

  • 12. Jukka-Pekka, Spets
    et al.
    Petri, Kanninen
    Tanja, Kallio
    Jorma, Selkainaho
    Yohannes, Kiros
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kari, Saari
    Martti, Larmi
    Test of Different Anode Electrocatalysts for Direct Glucose Anion Exchange Membrane Fuel Cell2016In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 11, no 6, p. 4219-4230Article in journal (Refereed)
    Abstract [en]

    Direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutral-state electrolyte of 0.1 M [PO4] (tot) was studied with five different anode electrocatalysts (Pt, PtRu, PtNi, Au, PdAu) at a temperature of 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was Pt supported on carbon (60 wt.%). Four anode electrocatalysts (supported on carbon) had a total metal content of 40 wt.% while the fifth anode material of PtRu had a higher content of 60 wt.%. Moreover, in order to show the influence of the metallic content on the fuel cell performance, anode catalysts with 60 wt.% (Pt) and 10wt.% (PtNi) were tested. The operation of the AEMFC was controlled by means of an in-house-made electronic load with PI-controller (i.e. a feedback controller that has proportional and integral action on control error signal) either at constant current (CC) or at constant voltage (CV). The primary objective was to characterize the Coulombic efficiency (CE) based on the exchange of two electrons and compare the specific energy (Wh kg(-1)) for the direct glucose AEMFC related to the different electrode combinations and electrocatalysts. As a result of these screening tests, two most efficient anode electrodes with Pt and PtNi were selected to be used for further AEMFC studies.

  • 13.
    Kiros, Yohannes
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Electrocatalytic Properties of Co, Pt, and Pt-Co on Carbon for the Reduction of Oxygen in Alkaline Fuel Cells1996In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 143, p. 2152-2157Article in journal (Refereed)
    Abstract [en]

    The effect of cobalt, platinum, and cobalt-platinum, alloys on high surface area carbons for oxygen reduction in alkaline electrolyte was investigated. The Pt-Co catalyst with ca. 1:3 atomic ratio was prepared by addition of H2PtC16 solution to a mixture of methanol and a 5% surfactant in deionized water containing cobalt acetate and carbon suspension. This was followed by drying and heat-treatment at 700 and 900°C in a flow of hydrogen and nitrogen gas mixtures. Polarization curves and kinetic parameters for Pt, Co, and Pt-Co were conducted and compared in 6 M KOH and at 80°C. Higher activities were observed for the Pt-Co alloy, that had been heat treated at 900°C. In addition to increased activity of this catalyst, the unalloyed base metal (Co) contributes to total performance improvement of the oxygen reduction process. Furthermore, surface, structural, and chemical characterizations of the catalysts were carried out using transmission electron microscopy, x-ray diffraction, Brunauer, Ermnett, and Teller method, and atomic absorption spectroscopy. Dissolution of cobalt from the electrodes, both from the single cobalt phase and Pt-Co alloy catalysts, has been established. The x-ray results demonstrated a shift to lower lattice parameters (3.618 A) by the Pt-Co alloys, prepared at 90 0°C, than the pure platinum catalyst (3.9 19 A).

  • 14.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Metal porphyrins for oxygen reduction in PEMFC2007In: International Journal of Electrochemical Science, ISSN 1452-3981, Vol. 2, no 4, p. 285-300Article in journal (Refereed)
    Abstract [en]

    A short literature review on alternative catalysts for the cathodic oxygen reduction in acid (H2SO4) and polymer electrolyte membrane fuel cell ( PEMFC) with special emphasis on pyrolyzed macrocycles and precursor materials from metals, organic molecules and N-containing elements has been conducted. Furthermore, various catalytic materials comprising two different concentrations of iron and cobalt tetramethoxyphenyl porphyrins and perovskites were prepared by both the impregnation and precipitation reactions. Screening tests of the individual catalytic materials and their mixtures were carried out in half-cell measurements using the rotating disc electrode (RDE) in 0.5M H2SO4 and at room temperature. Cyclic voltammograms were recorded at a scan rate of 10 mV s(-1) both with and without rotations. The peak potential at 0 rpm was used to study and compare the catalytic activities towards oxygen reduction reaction (ORR). Concentrations of 30wt% Fe and Co/TMPP have shown increased performance characteristics, while those with lower or increased contents, acid-treated and mixed with perovskite have displayed lower activities. Polarization data for the catalyst containing 30wt% FeTMPP was also obtained. Acid leaching of the pyrolysis products has resulted in substantial decrease of the metals from the pyrolysis products supported on carbon. TEM, BET-surface area and EDX analyses on the samples have shown high aggregation of the metals with crystalline structure, surface areas depending on the compositions of the catalysts and increased surface concentration of the metals with absence of nitrogen on the moiety.

  • 15.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Oxygen reduction electrode2002Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The invention refers to an oxygen reduction electrode comprising at least three layers: a current collector, a diffusion layer comprising at least PTFE; and a catalytical active layer comprising at least a mixture of perovskites and pyrolysed macrocycles. In this way, oxygen may be utilised from air without an initial removal of carbon dioxide. Moreover, the invention refers to methods for preparing the electrode, as well as fuel cells and other products wherein the electrode can be used.

  • 16.
    Kiros, Yohannes
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Separation and permeability of zincate ions through membranes1996In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 62, p. 117-119Article in journal (Refereed)
    Abstract [en]

    A novel method for the separation of zincate ions in alkaline media has been developed. This development uses a precipitation reaction of Mn(OH)2 and application on a microporous separator (Celgarde). The amount of zinc, passed through the membranes was estimated by electrogravimetric method. Different inorganic materials in combination with the separator material have been tested. Effective low grade permeability of zincate ions and increased resistivities have been found to he related to the amount of Mn(OH)2 applied on the separator.

  • 17.
    Kiros, Yohannes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Bursell, Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Low energy consumption in chlor-alkali cells using oxygen reduction electrodes2008Article in journal (Refereed)
    Abstract [en]

    An air/oxygen gas diffusion electrode for use as a cathode to replace the traditional hydrogen-evolving electrode in chlor-alkali electrolysis was assessed. Attempts to stabilize the cathode have been addressed in order to circumscribe problems associated with "flooding" or "wetting-in" properties. Variation of the hydrophobic concentration in the gas diffusion layer had a significant effect on the electrochemical tests of both the half-cell and electrolysis of the chlor-alkali cells. Life-tests as well as performance characteristics for both types of cells have shown encouraging results at NaOH concentration levels of ca 8M NaOH and temperatures of 70 and ca. 80 degrees C, respectively. Though cell voltages of about 2V were achieved and thereby reducing the energy consumption by 30-35% compared to the state-of-the-art membrane cell, the contributions of overvoltages were still high compared to the equilibrium potential of about 1.23V. Efforts to limit the individual parts of overvoltages as well as maintenance of the zero-gap cell at least on the anode side have been carried out. Two different kinds of cation exchange membranes have been used for the electrolysis cell. However, the cation exchange membrane with hydrophilic properties having high initial performances showed tendencies of blister formations.

  • 18.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Liu, X. R.
    Zhu, Bin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Cost-effective perovskite for intermediate temperature solid oxide fuel cells (ITSOFC)2001In: Journal of New Materials for Electrochemical Systems, ISSN 1480-2422, Vol. 4, no 4, p. 253-258Article in journal (Refereed)
    Abstract [en]

    Low lanthanum containing perovskite, Ca0.9La0.1MnO3 (CLM) was synthesized. The material was characterized and examined as a cathode for the intermediate temperature (400 to 650C) solid oxide fuel cell (ITSOFC) applications. ITSOFCs using this cost-effective perovskite as a cathode displayed an excellent cell performance: between 300 and 1500 mA/cm(-2) (100 to 500 mWcm(-2)) for temperatures ranging from 450 to 600 degreesC. The role of AgO as additive to the perovskite has also showed an enhancement in the fuel cell performance.

  • 19.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Majari, M.
    Nissinen, T. A.
    Effect and characterization of dopants to Raney nickel for hydrogen oxidation2003In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 360, no 02-jan, p. 279-285Article in journal (Refereed)
    Abstract [en]

    Raney nickel and its alloys with the transition metals were prepared and investigated as gas diffusion electrodes for the hydrogen oxidation reaction (HOR) in 6 M KOH and at 60degreesC. The spongy Raney nickel prepared by a mixture of Ni and Al with a weight ratio of 1: 1 was compared for the catalytic activity as hydrogen electrodes with other alloy formations containing 2 wt.% of Cu, Fe, Cr, Ti and La. Depending on the composition of the active layer, the electrocatalytic activity of the Raney nickel was found to decrease in a descending order of the doped metals: Cr>La>Ti>Cu>Fe and with no admixture. The catalytic response of the electrodes, especially for the Cr and Ti-based Raney Ni showed high enrichment and aggregation on the surface and hence affects the activity and stability. Surface area, particle size. average pore diameter, particle morphology and surface elements of the various alloy combinations, have been analyzed and assessed using BET-specific surface areas, SEM and EDXS.

  • 20.
    Kiros, Yohannes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Myrén, Carin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Schwartz, S.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sampathrajan, A
    Tamil Nadu Agricultural University.
    Ramanathan, M
    Tamil Nadu Agricultural University.
    Electrode R&D, stack design and performance of biomass-based alkaline fuel cell module1999In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 24, p. 549-564Article in journal (Refereed)
    Abstract [en]

    Electrode formulations with di}erent materials and manufacturing techniques were tested electrochemically in order to assess their stability and activity in long!term operations. Cathode electrocatalysts such as CoTPP, Ca0.9La0.1MnO3 and Pt-Co alloys were incorporated in high surface area carbons and operated at a constant load of 100 mA cm-2 80C and an electrolyte concentration of 6M KOH. Similarly, anode catalysts with Pt-Pd bimetallic combinations were also tested and ascertained in half!cell measurements. Surface area measurements and Transmission Electron Microscopy (TEM) analyses were carried out both before and after the electrochemical test procedures. The electrodes were incorporated into a seven and two cell module design of the external and internal manifolding types and the experiences gained from these design principles are described, respectively. Furthermore, a biomass fed AFC module with all the system descriptions, steps, and a demonstration layout of producer gas to alkaline fuel cell are examined and discussed. Wood charcoal and agro-residues were used as feedstock and as a primary fuel. Power output of the different feedstock in a producer gas fed alkaline fuel cell has the shown potentiality and effciency to be applied as a stand alone power generator.

  • 21.
    Kiros, Yohannes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pirjamali, M.
    Bursell, Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Oxygen reduction electrodes for electrolysis in chlor-alkali cells2006In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, no 16, p. 3346-3350Article in journal (Refereed)
    Abstract [en]

    Oxygen reduction electrodes, containing non-noble metal catalysts supported on high surface area carbon and wet-proofed with PTFE were tested under reaction conditions for the chlor-alkali electrolysis. Double-layer gas diffusion electrodes were prepared by rolling of an active layer and diffusion layer on a nickel wire screen, compressed and sintered at 300 degrees C. Electrochemical measurements for substantiating the activity and stability of the half-cells were conducted in 8 M NaOH by supplying oxygen at a cell temperature of 70 degrees C and a constant current load of 300 mA cm(-2). An electrolysis cell with a dimensionally stable anode (DSA) and double-layered cathode was assembled, where 4.8 M NaCl and oxygen were supplied, respectively, for the production of chlorine and NaOH. The cell performances as well as stability of the electrodes were investigated at about 80 degrees C. This study shows that by replacing the high voltage consuming hydrogen-evolving reaction and by adopting highly active electrocatalysts as cathode materials, energy savings of more than 30% could be realized.

  • 22.
    Kiros, Yohannes
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Pirjamali, Massoud
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Preparation of high surface area La0.1Ca0.9MnO3 and its electrochemical activities2007In: THERMEC 2006, Pts 1-5 / [ed] Chandra, T; Tsuzaki, K; Militzer, M; Ravindran, C, 2007, Vol. 539-543, p. 1361-1366Conference paper (Refereed)
    Abstract [en]

    The use of perovskites as potential heterogeneous catalysts in a number of chemical and electrochemical reactions have attracted the research interest due to high surface reactivity and low cost. Since catalysis is strongly dependent on surface areas, texture and structural homogeneity, the development of effective modes of preparation of perovskites is of utmost importance for the achievement of high performances, especially for electrochemical applications in fuel cells and metal/air batteries. The precipitation reaction method for the synthesis of La0.1Ca0.9MnO3 at low temperatures in the presence of alkaline support electrolyte has shown significant gain in the surface and electrochemical properties. Enhanced BET-surface area of this production method as compared to the dry pyrolysis method was obtained. Multifunctional application for cathodic reactions in alkaline fuel cell (AFC) and intermediate temperature solid oxide fuel cell (IT-SOFC) as well as for bifunctional systems of both oxygen reduction reaction (orr) and oxygen evolution reaction (oer) has been investigated. Parameter optimisations of the ingoing materials and analyses of the solid-state properties of the catalyst pertaining to structural, chemical and surface characteristics have also been carried out.

  • 23.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Quatrano, Tamara
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Determination of the thicknesses of the active layer and cathode limiting currents in AFC2004In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 6, no 6, p. 526-530Article in journal (Refereed)
    Abstract [en]

    A series of double-layered gas diffusion electrodes with two different electrocatalysts, i.e., Ag and pyrolyzed macrocycle mixture (PMM) were prepared in order to find out the maximum limiting current densities (i(L)) by varying the oxygen partial pressures in 6 M KOH and at 65 degreesC. As optimization of the active (catalyst) layer is important for better utilization of the catalytic reactions for oxygen reduction and thereby attainment of high current density, electrochemical measurements in half-cells were carried out to substantiate the current-thickness relationships. The thicknesses for both the active layers and diffusion layers were determined by using SEM. i(L) for an oxygen concentration simulating that of air was found to be 2.2 A cm(-2) for the PMM with 0.51 mm and 1.6 A cm-2 for the Ag-based catalyst with 0.56 mm thicknesses of the active layer. An overlay of a mathematical model, describing the parameters for determination of i(L), has also been inserted alongside the experimental values.

  • 24.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Schwartz, S.
    Long-term hydrogen oxidation catalysts in alkaline fuel cells2000In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 87, no 02-jan, p. 101-105Article in journal (Refereed)
    Abstract [en]

    Pt/Pd bimetallic combination and Raney Ni catalysts were employed in long-term electrochemical assessment of the hydrogen oxidation reaction (HOR) in 6 M KOH. Steady-state current vs. potential measurements of the gas diffusion electrodes have shown high activity for these types of catalysts. Durability tests of the electrodes have shown increased stability for the Pt/Pd-based catalysts than the Raney Ni at a constant load of 100 mA/cm(2) and at temperatures of 55 degrees C and 60 degrees C, respectively. Surface, structural and chemical analyses by BET surface area, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to characterize the composite electrode/catalyst both before and after the electrochemical testing.

  • 25.
    Kiros, Yohannes
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Shimamune, Takayuki
    Gas diffusion electrode2012Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A method of preparing a gas diffusion electrode comprising a diffusion layer, and a reaction layer arranged to eachother, wherein the diffusion layer is prepared by i) admixing a) sacrificial material, b) polymer and c) a metal - based material and d)optional further components, wherein the sacrificial material has a release temperature below about 275 °C and is added in anamount from about 1 to about 25 wt% based on the total weight of components a) -d) admixed; ii) forming a diffusion layer from theadmixture of step i); iii) heating the forming diffusion layer to a temperature lower than about 275 °C so as to release at least a partof said sacrificial material from the diffusion layer. A gas diffusion electrode comprising a diffusion layer and a reaction layer ar -ranged to one another, wherein the diffusion layer has a porosity ranging from about 60 to about 95 %, and an electrolytic cell comprising the electrode. An electrolytic cell, a fuel cell comprising the gas diffusion electrode and a metal-air battery comprising thegas diffusion electrode.

  • 26. Lampinen, Markku J.
    et al.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Spets, Jukka-Pekka
    Anttila, Tomi
    Research on bioorganic fuels as power sources2010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 22, p. 12635-12641Article in journal (Refereed)
    Abstract [en]

    This paper deals with the kind of the bioorganic fuel cells that are equipped with or without ion exchange membranes The bioorganic materials of interest are alcohols (methanol ethanol) and glucose which are obtained from renewable energy sources such as biomass The operation temperatures of the direct fuel cells cover from room temperature up to 150 C The direct bioorganic fuel cells belong to the subject area of Advanced fuel cells of the Working group 4 in the EU COST Action 543 among the collaborating Universities and Institutes Bioorganic fuel cells are suitable for application in small portable power sources such as backups battery chargers and in electronic devices A number of current and earlier works are summansed and advances are highlighted in this area with special emphasis on glucose as a fuel.

  • 27. Marini, S.
    et al.
    Salvi, P.
    Nelli, P.
    Pesenti, R.
    Villa, M.
    Berrettoni, M.
    Zangari, G.
    kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Advanced alkaline water electrolysis2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 82, p. 384-391Article in journal (Refereed)
    Abstract [en]

    A short review on the fundamental and technological issues relevant to water electrolysis in alkaline and proton exchange membrane (PEM) devices is given. Due to price and limited availability of the platinum group metal (PGM) catalysts they currently employ, PEM electrolyzers have scant possibilities of being employed in large-scale hydrogen production. The importance and recent advancements in the development of catalysts without PGMs are poised to benefit more the field of alkaline electrolysis rather than that of PEM devices. This paper presents our original data which demonstrate that an advanced alkaline electrolyzer with performances rivaling those of PEM electrolyzers can be made without PGM and with catalysts of high stability and durability. Studies on the advantages/limitations of electrolyzers with different architectures do show how a judicious application of pressure differentials in a recirculating electrolyte scheme helps reduce mass transport limitations, increasing efficiency and power density.

  • 28. Marini, S.
    et al.
    Salvi, P.
    Nelli, P.
    Pesenti, R.
    Villa, M.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Oxygen evolution in alkali with gas diffusion electrodes2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 26, p. 11496-11506Article in journal (Refereed)
    Abstract [en]

    Progresses in the area of the oxygen evolution reaction (OER) are now occurring at a much faster rate relative to few years ago. For this reason, it has been deemed appropriate to present a critical review of the major and most recent contributions towards a fundamental understanding of what determines the OER electrocatalytic properties of a material. Furthermore, the technologies used to produce practical OER electrodes with top activities are assessed and the current benchmarks of performance are identified. Furthermore, results pertaining to our work on Raney-Ni gas diffusion anodes, which have been optimized in thickness and composition, are presented. An addition of 10 wt.% of a Co3O4 micrometric powder as co-catalyst (with Raney Ni-Fe) was found to enhance the polarization behavior and performance. The electrode so obtained achieves activities comparable with those of the best electrodes reported in the literature. Great emphasis has been placed in the analysis of the stability of the prepared Gas Diffusion Electrodes. Most of the GDEs were found to be stable in weeks long experiments with intermittent operation. The issue of integrating several functional layers (gas diffusion layer, active layer with current collector, separator layer) within a single, mechanically strong electrode assembly is briefly addressed.

  • 29. Marini, S.
    et al.
    Salvi, P.
    Nelli, P.
    Pesenti, R.
    Villa, M.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Stable and inexpensive electrodes for the hydrogen evolution reaction2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 26, p. 11484-11495Article in journal (Refereed)
    Abstract [en]

    The HER activities of Raney-Ni electrodes obtained by partial leaching of Al in a Ni-Al-Fe alloy doped with Mo, Cr or Pd were studied in 28% KOH. PTFE bonded Gas Diffusion Electrodes (GDEs) were prepared by the rolling method before sintering at 300 degrees C under N-2. Ni in alkaline electrolyte has a lower intrinsic HER activity than Pt in acid. However, the spongy and highly porous character of Raney-Ni greatly enhances HER resulting in a cheap material with outstanding catalytic performance. The polarization behavior of GDEs consisting mainly of Raney-Ni catalysts with optional addition of co-catalyst or conductivity enhancing powders, such as carbonyl iron, carbonyl nickel, copper and molybdenum oxide are studied as a function of temperature and time in order to determine activities, behavior in the high current density regime, and long term stability in view of potential exploitation in industrial electrolysis. Cr and Pd-doped Raney-Ni initially achieve outstanding performances with unusually low "Tafel slopes". After weeks long cathodic treatments, these GDEs eventually attain inferior but stable activities due to an apparently irreversible aging of Raney-Ni. The aging of Mo-doped Raney-Ni is less conspicuous, and relevant performances are sometimes improved by additives. A clear picture is emerging of the mechanisms controlling polarization and aging behavior of Raney-Ni GDEs. From this picture, suggestions are put forward on how to improve stability and performances of full electrode assemblies and make them suitable for use in advanced alkaline electrolyzers.

  • 30.
    Menya, E.
    et al.
    Makerere Univ, Coll Engn Design Art & Technol, Dept Mech Engn, POB 7062, Kampala, Uganda.;Gulu Univ, Dept Biosyst Engn, POB 166, Gulu, Uganda..
    Olupot, P. W.
    Makerere Univ, Coll Engn Design Art & Technol, Dept Mech Engn, POB 7062, Kampala, Uganda..
    Storz, H.
    Thuenen Inst Agr Technol, Bundesallee 47, D-38116 Braunschweig, Germany..
    Lubwama, M.
    Makerere Univ, Coll Engn Design Art & Technol, Dept Mech Engn, POB 7062, Kampala, Uganda..
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Characterization and alkaline pretreatment of rice husk varieties in Uganda for potential utilization as precursors in the production of activated carbon and other value-added products2018In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 81, p. 104-116Article in journal (Refereed)
    Abstract [en]

    In this study, 13 rice husk (RH) varieties from 4 agro-ecological zones in Uganda were characterized, NaOH-pretreated, and evaluated for their potential utilization as precursors for production of bio-oil, ash, char, and activated carbon for selected applications. RH varieties were characterized through particle size analysis, bulk density, proximate and ultimate analyses, specific surface area, pore volume, as well as lignocellulosic and inorganic compositions. Selected RH varieties were subsequently pretreated at NaOH concentrations of 1-4%w/v, using pretreatment ratios of 5 g RH: 40 mL NaOH. Properties varied among RH varieties, suiting them as feedstocks for different applications. Upland rice husk varieties are more suited precursors for production of bio-oil, and activated carbon due to their relatively lower ash content, higher specific surface area, as well as higher volatile matter and fixed carbon contents. Upland rice husks could as well be employed in the preparation of electrodes for electrochemical devices, due to their relatively higher specific surface area. A high ash content (21-32% dry basis) of lowland rice husks presents good prospects for their calcination, since larger amounts of rice husk ash could be obtained, and employed in different applications. Lowland rice husk varieties could also be more suited precursors for production of char for soil amendment, due to their relatively higher ash content, which subsequently increases their char yields. However, alkaline pretreatment of rice husks using 2-4%w/v NaOH can reduce the ash content by as much as 74-93%, depending on the rice husk variety, which paves way for utilizing rice husks with a high ash content in different applications. Aside from ash reduction, the enhanced specific surface area (1.2-1.7 m(2) g(-1)), volatile matter (68-79%db) and fixed carbon (19-24%db) contents of NaOH-pretreated rice husks suggests they are more suited feedstocks than when employed in their raw form, for production of bio-oil, as well as activated carbon.

  • 31. Menya, E.
    et al.
    Olupot, P. W.
    Storz, H.
    Lubwama, M.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Production and performance of activated carbon from rice husks for removal of natural organic matter from water: A review2018In: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 129, p. 271-296Article, review/survey (Refereed)
    Abstract [en]

    Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. To address these limitations, research efforts have been focused on finding low cost materials that can be transformed into activated carbon. Rice husk is one of such materials of research focus, especially in the developing countries, where over 96% of rice husks are generated globally. Although numerous investigations have been made concerning the production of activated carbon from rice husks, the existing scientific information still remains widely scattered in literature. Furthermore, the scientific information regarding performance of rice husk activated carbon during NOM removal from water still remains poorly documented. This review article therefore provides ample information on efforts made by various researchers concerning production of activated carbon from rice husks and its adsorption performance in relation to NOM removal from water. Properties and pretreatment of rice husks in relation to production of activated carbon are discussed. Activation of rice husks by physical and chemical methods under numerous conditions is reviewed. Factors affecting NOM adsorption by activated carbon are briefly discussed. Adsorption performance of rice husk activated carbon is also reviewed with respect to NOM removal from water, and where possible compared with other source derived activated carbons. The data from literature revealed that NOM removal by rice husk activated carbon can be as effective as commercial activated carbon. Consequently, rice husk activated carbon has potential to serve as an alternative to commercial activated carbon.

  • 32. Menya, E.
    et al.
    Olupot, P. W.
    Storz, H.
    Lubwama, M.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    John, M. J.
    Effect of alkaline pretreatment on the thermal behavior and chemical properties of rice husk varieties in relation to activated carbon production2019In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926Article in journal (Refereed)
    Abstract [en]

    Thermal behavior and chemical properties of selected raw and NaOH-pretreated rice husk varieties were investigated. NaOH-pretreatment process involved soaking 5 g rice husk samples in 40 mL of 2%w/v NaOH, shaking (400 rpm) and heating (50 °C) for 3 h. NaOH-pretreated samples were water-washed, oven-dried, and milled for use in the determination of their thermal behavior and surface functional groups. Alkaline wash-water was also analyzed for sugar components. Thermal decomposition temperatures, degradation rates, and the subsequent mass losses varied from one rice husk variety to another. These thermal properties increased after NaOH-pretreatment of the rice husk varieties, reducing their char yields (17.1–20.4% db). These changes mainly had to do with the lignin, hemicellulose, and ash removal from the rice husk varieties, as confirmed by their FTIR analysis, as well as by the sugar composition analysis of their alkaline wash-water. Consequently, the FTIR spectra differed between the raw and NaOH-pretreated rice husk varieties.

  • 33.
    Menya, E
    et al.
    Department of Mechanical Engineering, Makerere University, Uganda.
    Olupot, P W
    Department of Mechanical Engineering, Makerere University, Uganda.
    Storz, H
    Thünen Institute of Agricultural Technology, Braunschweig, Germany.
    Lubwama, M
    Department of Mechanical Engineering, Makerere University, Uganda.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    John, MJ
    P0lymer and Composite Unit, Council for Scientific and Industrial Research, Port Elizabeth, South Africa.
    Optimization of pyrolysis conditions for char production from rice husks and its characterization as a precursor for production of activated carbon2019In: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Response surface methodology was employed to optimize pyrolysis conditions for production of char with maximumyield, fixedcarbon content, and with minimum ash content from Uganda’s New Rice for Africa (NERICA) 1 rice husk variety. The aim wasto obtain rice husk char with more suitable properties as an activated carbon precursor. Mathematical models were developed toexplain the relationships between the experimental responses and the pyrolysis parameters of temperature (400–600 °C), heating rate (10–25 °C min−1), and heating period (60–120 min). The optimized rice husk char was further characterized for elementaland proximate compositions, thermal behavior, specific surface area, as well as surface functional groups. Results from theanalysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Pyrolysis temperature had thegreatest influence on each of the responses, followed by heating period, and lastly heating rate. Optimum pyrolysis conditionswere found to be temperature (406 °C), heating rate (10 °C min−1), and heating period (60 min), resulting in char yield, fixedcarbon, and ash contents of 35.26, 55.39, and 35.01% dry basis, respectively. Compared to raw rice husk, the resulting rice huskchar was found more suited as activated carbon precursor, due to its enriched carbon content (60.35%) and specific surface area (123.9 m2 g−1). Thermogravimetric analysis of the rice husk char revealed that thermal activation temperatures higher than 400 °C may be required to considerably devolatilize the char, forming a more porous activated carbon.

  • 34. Nissinen, T. A.
    et al.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Gasik, M.
    Leskela, M.
    MnCo2O4 preparation by microwave-assisted route synthesis (MARS) and the effect of carbon admixture2003In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 15, no 26, p. 4974-4979Article in journal (Refereed)
    Abstract [en]

    Catalyst spinel MnCo2O4 with particle size <30 nm was prepared by a novel microwave-assisted route. To determine the optimal amount of carbon needed as a microwave susceptor, varying amounts of amorphous carbon powder (7-26 wt %) were mixed with the aqueous solutions of Mn- and Co-nitrates. After heat treatment at 200degreesC in a conventional oven, the mixtures were heat-treated in a microwave oven (2.45 GHz) at a power of 350 W. The effect of the carbon amount on the formation and properties of the catalysts was studied. In this production method, 13 wt % of carbon was found to be the minimum needed for spinel MnCo2O4 formation. Most of the carbon was oxidized during the microwave treatment. When the carbon content in the nitrate-carbon mixture was increased beyond 13 wt %, the carbon content and the specific surface area of the final catalyst started to decrease. However, the carbon amount of 18 wt % in the initial nitrate-carbon mixture was found to be the most preferable when considering the catalytic activity of the spinel toward oxygen reduction reaction in alkaline electrolyte.

  • 35. Nissinen, T.
    et al.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Gasik, M.
    Lampinen, M.
    Comparison of preparation routes of spinel catalyst for alkaline fuel cells2004In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 39, no 9, p. 1195-1208Article in journal (Refereed)
    Abstract [en]

    MnCo2O4 has been used as a catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells due to easier production and lower costs compared to noble metals. A novel method using a microwave-assisted route of synthesis in the presence of amorphous carbon was developed resulting in MnCo2O4 with particle sizes

  • 36. Ossman, M. E.
    et al.
    Mansour, M. S.
    Fattah, M. A.
    Taha, N.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Peanut shells and talc powder for removal of hexavalent chromium from aqueous solutions2014In: BULGARIAN CHEMICAL COMMUNICATIONS, ISSN 0324-1130, Vol. 46, no 3, p. 629-639Article in journal (Refereed)
    Abstract [en]

    In this work, talc powder and peanut shells were investigated as potential adsorbents for the removal of hexavalent chromium from aqueous solutions. The effect of important parameters, such as contact time, solution pH and adsorbent dosage were also evaluated for the adsorption process of chromium (IV). The experimental data showed that a contact time of 30 min for peanut shells and 70 min for talc powder and pH of 4 were optimum for the adsorption to reach equilibrium. Furthermore, FT-IR, SEM and BET measurements were made in order to assess the physicochemical properties of the substrates. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were used to fit the equilibrium data, heat and energy of adsorption of both adsorbents. Determinations of the rate of adsorption using kinetic models follow pseudo-first order for peanut shells and talc powder with intraparticle diffusion.

  • 37.
    Ossman, M.E.
    et al.
    Pharos University in Alexandria.
    Abdelfatah, M
    Pharos University in Alexandria.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE).
    Preparation, Characterization and Adsorption Evaluation of old Newspaper Fibres using Basket Reactor (Nickel Removal by Adsorption)2016In: International Journal of Environmental Research, ISSN 1735-6865, E-ISSN 2008-2304, Vol. 10, no 1, p. 119-130Article in journal (Refereed)
    Abstract [en]

    In this work, old newspaper fibers (ONF) bleached with H2O2, treated with KOH and treatedwith NaOCl were investigated as potential adsorbents. The characterization of the produced fibers using FTIR,SEM and particle size distribution have been carried out and tested for the removal of Ni (II) from aqueoussolutions. The results indicated that the fibers treated with KOH give the highest %removal of Ni (II) with 88%. Two different reactor designs (batch and basket reactor) with different variables were studied. The results indicated that the equilibrium time was 30 min. and the removal of Ni (II) increased significantly as the pH increased from 2.0 to 6.0 and decreased at pH range of 6.5–8.0. The adsorption of Ni (II) onto ONF treatedwith KOH using batch and basket reactors follows the Langmuir isotherm. The pseudo second order kineticmodel provided good correlation for the adsorption of Ni (II) onto ONF treated with KOH for both batch and basket reactors.

  • 38.
    Paulraj, Alagar R.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte2018In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Non-precious metal bifunctional catalysts are of great interest for metal–air batteries, electrolysis, and regenerative fuel cell systems due to their performance and cost benefits compared to the Pt group metals (PGM). In this work, metal oxides of La0.1Ca0.9MnO3 and nano Co3O47 catalyst as bifunctional catalysts were used in oxygen reduction and evolution reactions (ORER). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption isotherms. The electrocatalytic activity of the perovskite-type La0.1Ca0.9MnO3 and Co3O4 catalysts both as single and mixtures of both were assessed in alkaline solutions at room temperature. Electrocatalyst activity, stability, and electrode kinetics were studied using cyclic voltammetry (CV) and rotating disk electrode (RDE). This study shows that the bifunctional performance of the mixed La0.1Ca0.9MnO3 and nano Co3O4 was superior in comparison to either La0.1Ca0.9MnO3 or nano Co3O4 alone for ORER. The improved activity is due to the synergistic effect between the La0.1Ca0.9MnO3 and nano Co3O4 structural and surface properties. This work illustrates that hybridization between these two metal oxides results in the excellent bifunctional oxygen redox activity, stability, and cyclability, leading to a cost-effective application in energy conversion and storage, albeit to the cost of higher catalyst loadings.

  • 39.
    Paulraj, Alagar Raj
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Chamoun, Mylad
    Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
    Svengren, Henrik
    Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
    Noréus, Dag
    Department of Materials and Environmental Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
    Göthelid, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Skårman, Björn
    Höganäs AB, SE-263 83 Höganäs, Sweden.
    Vidarsson, Hilmar
    Höganäs AB, SE-263 83 Höganäs, Sweden.
    Johansson, Malin B
    Division of Physical Chemistry, Department of Chemistry, The Ångström Laboratory, Uppsala University, P.O. Box 523, SE-75120 Uppsala, Sweden.
    Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes2019In: Batteries, E-ISSN 2313-0105, no 1Article in journal (Other academic)
    Abstract [en]

    Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

  • 40.
    Paulraj, Alagar Raj
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Johansson, Malin B
    Division of Physical Chemistry, Department of Chemistry, The Ångström Laboratory, Uppsala University, P.O. Box 523, SE-75120 Uppsala, Sweden.
    NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media2018In: catalyst, Vol. 8, no 8Article in journal (Refereed)
    Abstract [en]

    This article reports the two-step synthesis of NiFeOx nanomaterials and their characterization and bifunctional electrocatalytic activity measurements in alkaline electrolyte for metal-air batteries. The samples were mostly in layered double hydroxide at the initial temperature, but upon heat treatment, they were converted to NiFe2O4 phases. The electrochemical behaviour of the different samples was studied by linear sweep voltammetry and cyclic voltammetry on the glassy carbon electrode. The OER catalyst activity was observed for low mass loadings (0.125 mg cm−2), whereas high catalyst loading exhibited the best performance on the ORR side. The sample heat-treated at 250 °C delivered the highest bi-functional oxygen evolution and reduction reaction activity (OER/ORR) thanks to its thin-holey nanosheet-like structure with higher nickel oxidation state at 250 °C. This work further helps to develop low-cost electrocatalyst development for metal-air batteries

  • 41. Pirjamali, M.
    et al.
    Kiros, Yohannes
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Effects of carbon pretreatment for oxygen reduction in alkaline electrolyte2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 109, no 2, p. 446-451Article in journal (Refereed)
    Abstract [en]

    The effects of different media on carbon pretreatments for oxygen reduction in alkaline electrolyte without application of active electrocatalysts were examined. Low surface area Vulcan XC-72 and high surface area Ketjenblack EC-300 were subjected to aqueous acid (flouric or formic), gaseous (H-2, N-2 or CO2) and thermal treatments at 600 or 900 degreesC. Though non-scrubbed air was used, as a result of which carbonate build-up was high and peroxide concentration increased due to the electrode reaction, some of the electrodes resulted in life-tests of more than 2000 h at 65 degreesC, 6 M KOH with a constant load of 50 mA cm(-2) and intermittent polarisations at higher current densities. BET-surface areas and pH changes of more than 60% and weight losses of up to 15% of the carbon blacks were observed after the pretreatment steps. Electrochemical characterisation of the carbons showed that pretreatment steps of the carbon blacks have a significant effect on the long-term stability and activity of the gas diffusion electrodes in alkaline electrolyte.

  • 42.
    Rifau, Ali
    et al.
    University Sains Malaysia.
    Zainal, Zainal
    University Sains Malaysia.
    Mutharasu, D.
    Fauzi, A.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Zhu, Bin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Zanzi Vigouroux, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Performance study on an Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) fabricated by dry pressing method2006In: American Journal of Applied Sciences, ISSN 1546-9239, E-ISSN 1554-3641, Vol. 3, no 9, p. 2020-2024Article in journal (Refereed)
  • 43. Salvi, Paolo
    et al.
    Nelli, Paolo
    Villa, Marco
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Zangari, Giovanni
    Bruni, Gianna
    Marini, Amedeo
    Milanese, Chiara
    Hydrogen evolution reaction in PTFE bonded Raney-Ni electrodes2011In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, no 13, p. 7816-7821Article in journal (Refereed)
    Abstract [en]

    This study is concerned with the hydrogen evolution reaction (HER) in several PTFE bonded Raney-Ni electrodes as function of temperature and treatments. The Mo-doped Raney-Ni catalysts are activated by hours of long cathodic polarization interleaved with few deep "charge - discharge" (polarity reversal) cycles. Moreover, the HER efficiency of the electrode requires additives which enhance conductivity and surface properties: with powders of Ni alloys (Ni-Ti, Ni-Cr, Ni-Fe) the electrode becomes also more stable, and almost insensitive to polarity reversal. The main effect of a temperature increase is the reduction of the Tafel slope, which is about 120 mV/dec at 25 degrees C, and about 60 mV/dec at 60 degrees C. A proper choice of additives yield electrodes which withstand polarity reversal and may be used in electrolysers which are intermittently operated, or have anodes which require periodic in situ re-activation by reduction.

  • 44.
    Solis, Jerry L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE). UMSS Universidad Mayor de San Simón, Bolivia.
    Alejo, L.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Calcium and tin oxides for heterogeneous transesterification of Babasssu oil (Attalea speciosa)2016In: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 4, no 4, p. 4870-4877Article in journal (Refereed)
    Abstract [en]

    Non-edible oils and waste cooking oils are alternatives to uphold a sustainable large scale production of biodiesel considering large volumes and by-products. Babassu oil (Attalea speciosa) offers a challenging case study scenario for the preparation of a heterogeneous catalytic material. This study shows the binary synthesis of calcium and stannic oxide (CaO/SnO2) catalysts for transesterification of oils with high content of free fatty acids (FFAs). The catalysts were prepared with several mass ratios of CaO:SnO2 in the proportions of 1:4, 4:1, 7:3 and 1:1. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and N2-physisorption analyses. Biodiesel production was tested using a 23 full factorial design with variables such as temperature, methanol/oil molar ratio, and catalyst weight relative to oil. Such design statistically proved that there was no significant effect over the response variable. Furthermore a Box-Behnken design surface response analysis using the same three variables with three levels was performed with MATLAB showing a non-linear relation and statistical response of the optimal conditions for biodiesel production. The optimal experimental conditions were found to be 54.1°C, agitation speed at 250rpm with 6wt.% of CaO/SnO2 (7:3 mass ratio of the binary catalyst) and 10:1 (methanol:oil) molar ratio. The catalyst has shown a high potential for conversion of Babassu oil by fine-tuning as a single step by simultaneous esterification and transesterification to biodiesel.

  • 45.
    Solis, Jerry L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. Centro de Tecnologı´a Agroindustrial, FCyT, UMSS Universidad Mayor de San Simo´n, Cochabamba, Bolivia.
    Berkemar, Albin L.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alejo, Lucio
    Centro de Tecnologı´a Agroindustrial, FCyT, UMSS Universidad Mayor de San Simo´n, Cochabamba, Bolivia.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Biodiesel from rapeseed oil (Brassica napus) by supported Li2O and MgO2016In: International Journal of Energy and Environmental Engineering, ISSN 2008-9163, E-ISSN 2251-6832Article in journal (Refereed)
    Abstract [en]

    Vegetable oils are a vast triglyceride sourcefor biodiesel production; i.e. fatty acid methyl esters(FAME), with methanol and a catalyst via transesterification reaction. The aim of this work was to study heterogeneously catalysed biodiesel production with solid oxides such as mayenite (Ca12Al14O33) and alumina(Al2O3) as catalyst carriers using edible rapeseedoil as feedstock. These oxides were impregnated to have Li2O and MgO concentrations of 5–10 and 5–30 wt% oneach carrier, respectively. The catalysts were characterized using N2-physisorption (BET/BJH), scanning electronmicroscopy (SEM), and X-ray diffraction (XRD)analyses. The synthesized catalysts were mesoporous ranging from 119 to 401 A ° and their chemical phase composition was confirmed by the XRD. The catalyst coating (MgO/Li2O) was studied, along with the catalyst amount in the reactor and the assessment of the transesterification reaction kinetics. The reaction was studiedat 60 C, atmospheric pressure, agitation rate of180 rpm, and a reaction time of 2 h in a 6:1 molar ratioof methanol to oil. For each catalyst, loadings of 2.5, 5,and 10 wt% relative to the oil weight were evaluated.The highest biodiesel yield was obtained by 5 wt%(relative to oil weight) impregnated mayenite catalyst coated with 10 wt% of Li2O. The kinetic data fits to a pseudo-first-order model having a reaction rate constantequal to 0.045 min-1 under these mild reaction conditions.

  • 46.
    Solis, Jerry Luis
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Davila, R.
    Sandoval, C.
    Guzmán, D.
    Guzmán, H.
    Alejo, L.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Ethanol Production from Schinus molle Essential Oil Extraction Residues2019In: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265XArticle in journal (Refereed)
    Abstract [en]

    Abstract: The present study determines the best conditions for the fermentation of Schinus molle drupes by the combination of different types of hydrolysis with the search for an adequate yeast strain. Schinus molle seed residues from an essential oil extraction plant (EOEP) have a high potential for ethanol production. Native yeast strains were isolated from the residues and were used to ferment the lignocellulosic residues, along with baker’s yeast (Saccharomyces cerevisiae) at 30 °C and pH 5.5 for comparison. Morphological and biochemical characterizations were carried out on the isolated yeast strains. Thermogravimetric and high-performance liquid chromatography analyses were done on the S. molle seeds (fresh and residue) to determine the ethanol production potential. The followed methodology included increasing the sugar content by hydrolysis with chemical (sulphuric acid, acetic acid, and sodium hydroxide), physical (thermal, vacuum, and ultrasound), and enzymatic treatments (amyloglucosidase and α-amylase). Once the optimum combination of yeast-hydrolysis was determined, a comparison of the greenhouse gas emissions between the original and proposed processes was done. The fermentation of the residues might replace methane from uncontrolled decomposition and reduce the solid residues in 50%/day, hence the EOEP global warming potential is reduced by 47%. The yearly income was estimated to increase by USD 2592.50 from 6302.6 L of ethanol produced from the residues.

  • 47.
    Soroka, Inna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Bjervås, Jens
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ceder, J.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Wallnerström, G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Connan, Mallory
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Tarakina, N. V.
    Maier, Annika Carolin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kiros, Yohannes
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Particle size effect of Ag-nanocatalysts deposited on carbon as prepared by γ-radiation induced synthesis2019In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, article id 108370Article in journal (Refereed)
    Abstract [en]

    The effect of silver particle sizes on the catalytic performance of Ag/C electrodes for oxygen reduction reaction (ORR) was studied. The Ag particles were precipitated from AgNO3 solutions on Vulcan XC-72 carbon as support by γ-radiation induced synthesis method. The structural and morphological characterizations of the electrode materials were done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that particles with smaller diameters, 11 ± 6 nm, possess higher catalytic activity for ORR (50 mA/cm2 at 0.3 V) as compared to those with larger diameters, 41 ± 5 nm, ORR activity is 25 mA/cm2 at 0.3 V. The observed effect may be explained by an increased amount of low coordinated atoms in smaller particles as compared to the larger ones.

  • 48.
    Soroka, Inna
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Tarakina, Nadezda V.
    Hermansson, Anton
    KTH, School of Chemical Science and Engineering (CHE).
    Bigum, Lukas
    KTH, School of Chemical Science and Engineering (CHE).
    Widerberg, Rickard
    KTH, School of Chemical Science and Engineering (CHE).
    Andersson, Mikael S.
    Mathieu, Roland
    Paulraj, Alagar R.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Radiation-induced synthesis of nanoscale Co- and Ni-based electro-catalysts on carbon for the oxygen reduction reaction2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 30, p. 9995-10002Article in journal (Refereed)
    Abstract [en]

    A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by.-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3.4% Co and 0.4% Ni) after reduction by irradiation, both the Ni and Co-based gas diffusion electrodes showed high catalytic activity for oxygen reduction both at room temperature and at 60 degrees C.

  • 49. Spets, J. P.
    et al.
    Kuosa, M. A.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Anttila, T.
    Rantanen, J.
    Lampinen, M. J.
    Saari, K.
    Enhancement of glucose electro-oxidation by an external electromagnetic field in direct-mode fuel cells2010In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, no 2, p. 475-479Article in journal (Refereed)
    Abstract [en]

    In this study a direct-mode fuel cell in which the fuel and electrolyte are mixed with each other is tested. An alkaline electrolyte is used. The direct-mode fuel cell is exposed to an externally generated electromagnetic field between electrodes to cause both the splitting of the fuel molecule into smaller units (i.e. electrochemical reforming) and an increase in the activity of catalyst materials on the fuel before electrochemical oxidation. The target is to create a fuel cell with a capacity range of a few mW cm(-2) with glucose as a fuel. In the selected fuel cell type with glucose as the fuel, a maximum current density of 13 mA cm(-2) was obtained. On the basis of the tests it seems to be possible to use the glucose-fuelled cell in small-scale applications, e. g. in small electronic devices.

  • 50.
    Spets, J. -P.
    et al.
    Helsinki University of Technology.
    Kuosa, M.
    Helsinki University of Technology.
    Granström, T.
    Helsinki University of Technology.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Rantanen, J.
    Helsinki University of Technology.
    Lampinen, M. J.
    Helsinki University of Technology.
    Saari, K.
    Helsinki University of Technology.
    Production of glucose by starch and cellulose acid hydrolysis and its use as a fuel in low-temperature direct-mode fuel cells2010In: THERMEC 2009, PTS 1-4 / [ed] Chandra, T; Wanderka, N; Reimers, W; Ionescu, M, Berlin, 2010, Vol. 638-642, p. 1164-1169Conference paper (Other academic)
    Abstract [en]

    The use of glucose, which is produced from the acid hydrolysis of starch and cellulose, is studied as a fuel in a low-temperature direct-mode fuel cell (LTDMFC) with an alkaline electrolyte. Glucose is regarded as being as good a fuel as bioethanol, because both the fuels give 2 electrons per molecule in the fuel cell without carbonisation problems. However, glucose can be produced with fewer processing stages from starch and cellulose than can bioethanol. In the LTDMFC the fuel and the electrolyte are mixed with each other and the fuel cell is equipped only with metal catalysts. Cellulose as a fuel is of great importance because the fuel for the energy production is not taken from food production. A description of an acid hydrolysis method for starch and cellulose is presented. Values for glucose concentrations in each hydrolysate are analysed by means of a chromatographic method. Each glucose hydrolysate was made alkaline by adding of potassium hydroxide before feed in the fuel cell. Polarisation curves were measured, and they were found to produce lower current density values when compared to earlier tests with pure glucose. The Coulombic efficiency of pure glucose electrochemical oxidation in LTDMFC, which was calculated from a ratio of detected current capacity (As) to the maximum current capacity with the release of two electrons per molecule, was also found to be very low. Concerning the hydrolysates, the glucose concentrations were found to have values that were too low when compared to the earlier tests with pure glucose in a concentration of 1 M. The further development demands for the system under consideration are indicated. The concentration of glucose in the hydrolysate is essential to achieve high enough current density values in the LTDMFC.

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