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Studies on Rechargeable Fe-air electrodes in Alkaline electrolyte
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy storage system is an important component in the energy system based on variable renewable energy sources into the grid. Energy storage system could contribute to decarbonization, energy security, offset the demand and supply of the electricity sector, especially for the electric grid. These can be either mechanical, electrochemical, chemical, electromagnetic or thermal devices. The most important functional characteristics of an energy storage system are capital cost, roundtrip efficiency, energy and power rating, response times and cycle life. Electrochemical energy storage systems (EES) have the following edge over the other systems: fast response time, relatively short duration of storage, size, high efficiency, a decentralized installation which is closer to generation or consumption site.

The focus of this thesis is on the development of cost-effective iron anode materials and electrocatalytic air electrodes for Fe-air batteries that potentially could become as an energy storage system. Iron-based systems are attractive due to their safety, cheapness, non-toxicity and ubiquitous availability of materials. However, both the anode and cathode parts have numerous drawbacks that need to be addressed. The anode exhibits poor charge efficiency, rate capability and low capacity utilization while the cathode has sluggish kinetics, poor activity, structural stability and the numbers of active non-noble metal catalysts are limited.

This work utilized Cu and Sn-doped iron nanomaterials and different additives (Bi2S3, CNT, LiOH) to enhance the performance of the iron electrode. The performance of the electrodes were evaluated using the charge/discharge cycling, rate capability, cyclic voltammetry (CV), galvanostatic and potentiodynamic polarization measurements, in operando charging measurements combined with mass spectrometry. The fresh and cycled electrodes and powders were characterized by ex-situ XRD, BET, SEM, TEM , XPS and Raman spectroscopy. The most striking results are the prevention of nanoparticle agglomeration, increased charging efficiency (80-91%), effect of Cu and Sn dopants on specific capacity (367-603 mAh g-1) and improved performance of the electrodes at high charge current densities.

In the subsequent air electrode part, non-precious metal La-doped CaMnOx, nano Co3O4 and NiFeOX electrocatalysts were synthesized using co-precipitation and hydrothermal methods. Both the single and mixed catalysts were used as bi-functional catalysts for oxygen reduction and evolution reactions (ORER). The catalysts were characterized by XRD, SEM, TEM, BET, Raman and XPS. The electrocatalytic activity and stability were assessed in alkaline solutions on gas diffusion electrodes and glassy carbon electrode by linear sweep voltammetry (LSV), CV and rotating disk electrode (RDE). Furthermore, the mixed catalyst and NiFeOX showed excellent bifunctional performance such as high activity and stability achieved by the hybridization of the two catalysts and the effect of catalyst loading on the electrocatalytic performance. These findings can help to develop a cost-effective material for Fe-air batteries.

Place, publisher, year, edition, pages
Stockholm: KTH , 2019. , p. 108
Keywords [en]
Fe-air battery; Cu/Sn-doped nanostructured iron electrodes, Alkaline electrolytes, Bi-functional OER/ORR catalyst, perovskite/spinel catalyst, NiFeOx, air electrode
National Category
Engineering and Technology Chemical Process Engineering Chemical Sciences
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-241534ISBN: 978-91-7873-087-2 (electronic)OAI: oai:DiVA.org:kth-241534DiVA, id: diva2:1281953
Public defence
2019-03-01, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 39078-1
Note

QC 20190124

Available from: 2019-01-24 Created: 2019-01-23 Last updated: 2019-02-22Bibliographically approved
List of papers
1. Core/shell structure nano-iron/iron carbide electrodes for rechargeable alkaline iron batteries
Open this publication in new window or tab >>Core/shell structure nano-iron/iron carbide electrodes for rechargeable alkaline iron batteries
2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 7, p. A1665-A1672Article in journal (Refereed) Published
Abstract [en]

In this work, we have studied a 2% copper substituted core shell type iron/iron carbide as a negative electrode for application in energy storage. The NanoFe-Fe3C-Cu delivered 367 mAh g−1 at ≈80% current efficiency, successfully running for over 300 cycles. The superior electrode kinetics and performance were assessed by rate capability, galvanostatic, potentiodynamic polarization measurements in 6 M KOH electrolyte and at ambient temperature. Ex-situ XRD characterizations and SEM images of both the fresh and used electrode surfaces show that nanoparticles were found to be still intact with negligible particle agglomeration. The electrodes have shown stable performances with low capacity decay, whereas sulfur dissolution from the additive Bi2S3 was found to decrease the charging efficiency with time. This core-shell type structured nano material is, consequently, an auspicious anode candidate in alkaline-metal/air and Ni-Fe battery systems.

Place, publisher, year, edition, pages
Electrochemical Society, 2017
Keywords
Renewable Energy Integration, Metal-Sulfide Additives, Electrochemical Properties, Anode Materials, Impedance Spectroscopy, Storage Systems, Performance, Carbon, Nanoparticles, Nanocomposites
National Category
Materials Chemistry
Research subject
Chemical Engineering; Chemistry
Identifiers
urn:nbn:se:kth:diva-210003 (URN)10.1149/2.1431707jes (DOI)000404397300042 ()2-s2.0-85020553265 (Scopus ID)
Funder
Swedish Energy Agency, 39078-1
Note

QC 20170627

Available from: 2017-06-27 Created: 2017-06-27 Last updated: 2019-01-24Bibliographically approved
2. La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte
Open this publication in new window or tab >>La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte
2018 (English)In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, p. 1-14Article in journal, Editorial material (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
National Category
Chemical Engineering
Research subject
Chemical Engineering; Chemistry
Identifiers
urn:nbn:se:kth:diva-222516 (URN)10.1007/s10008-017-3862-2 (DOI)000431668000007 ()2-s2.0-85040363046 (Scopus ID)
Funder
Swedish Energy Agency, 39078-01
Note

QC 20180212

Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2019-01-24Bibliographically approved
3. Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
Open this publication in new window or tab >>Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
Show others...
2019 (English)In: Batteries, E-ISSN 2313-0105, no 1Article in journal (Other academic) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Iron electrodes, Cu and Sn-doped iron, SWCNT and LiOH additives, charge efficiency, hydrogen evolution, GC-MS analysis
National Category
Chemical Process Engineering
Research subject
Chemistry; Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-241278 (URN)10.3390/batteries5010001 (DOI)000464125800001 ()
Note

QC 20190121

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-05-09Bibliographically approved
4. NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media
Open this publication in new window or tab >>NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media
2018 (English)In: catalyst, Vol. 8, no 8Article in journal (Refereed) Published
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

National Category
Other Chemical Engineering Chemical Process Engineering
Research subject
Chemical Engineering; Chemistry
Identifiers
urn:nbn:se:kth:diva-241281 (URN)10.3390/catal8080328 (DOI)000442517100033 ()2-s2.0-85052506473 (Scopus ID)
Funder
Swedish Energy Agency, 39078-01
Note

QC 20190124

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-08-20Bibliographically approved

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