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Publications (10 of 21) Show all publications
Zou, Y., Liu, Y., Wang, X., Sheng, G., Wang, S., Ai, Y., . . . Wang, X. (2017). Glycerol-Modified Binary Layered Double Hydroxide Nanocomposites for Uranium Immobilization via Extended X-ray Absorption Fine Structure Technique and Density Functional Theory Calculation. ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 5(4), 3583-3595
Open this publication in new window or tab >>Glycerol-Modified Binary Layered Double Hydroxide Nanocomposites for Uranium Immobilization via Extended X-ray Absorption Fine Structure Technique and Density Functional Theory Calculation
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2017 (English)In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 5, no 4, p. 3583-3595Article in journal (Refereed) Published
Abstract [en]

Novel, efficient, glycerol-modified nanoscale layered double hydroxides (rods Ca/Al LDH-Gl and flocculent Ni/Al LDH-Gl) were successfully synthesized by a simple one-step hydrothermal synthesis route and showed excellent adsorption capacities for U(VI) from aqueous solutions under various environmental conditions. The advanced spectroscopy analysis confirmed the existence of abundant oxygen-containing functional groups (e.g., C-O, O-C=O, and C=O) on the surfaces of Ca/AI LDH-Gl and Ni/Al LDH-Gl, which could provide enough free active sites for the binding of U(VI). The maximum adsorption capacities of Macro-application (Environment U(VI) calculated from the Sips model were 266.5 mg.g(-1) for Ca/Al LDH-Gl and 142.3 mg.g(-1) for Ni/Al LDH-Gl at 298.15 K, and the higher adsorption capacity of Ca/Al LDH-Gl might be due to more functional groups and abundant high-activity "Ca-O" groups. Macroscopic experiments proved that the interaction of U(VI) on Ca/Al LDH-Gl and Ni/Al LDH-Gl was due to surface complexation and electrostatic interactions. The extended Xray absorption fine structure analysis confirmed that U(IV) did not transformation to U(VI) on solid particles, and stable inner sphere complexes were not formed by reduction interaction but by chemical adsorption. The density functional theory (DFT) calculations further evidenced that the higher adsorption energies (i.e., E-ad = 4.00 eV for Ca/AI LDH-Gl-UO22+ and E-ad = 2.43 eV for Ca/Al LDH-Gl-UO2CO3) were mainly attributed to stronger hydrogen bonds and electrostatic interactions. The superior immobilization performance of Ca/AI LDH-Gl supports a potential strategy for decontamination of UO22+ from wastewater, and it may provide new insights for the efficient removal of radionuclides in environmental pollution cleanup.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keywords
Nanocomposites, Layered double hydroxides, Immobilization, U(VI), EXAFS
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-206255 (URN)10.1021/acssuschemeng.7b00439 (DOI)000398429700088 ()2-s2.0-85016790731 (Scopus ID)
Note

QC 20170512

Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2017-06-30Bibliographically approved
Yu, S., Wang, X., Yao, W., Wang, J., Ji, Y., Ai, Y., . . . Wang, X. (2017). Macroscopic, Spectroscopic, and Theoretical Investigation for the Interaction of Phenol and Naphthol on Reduced Graphene Oxide. Environmental Science and Technology, 51(6), 3278-3286
Open this publication in new window or tab >>Macroscopic, Spectroscopic, and Theoretical Investigation for the Interaction of Phenol and Naphthol on Reduced Graphene Oxide
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2017 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 6, p. 3278-3286Article in journal (Refereed) Published
Abstract [en]

Interaction of phenol and naphthol with reduced graphene oxide (rGO), and their competitive behavior on rGO were examined by batch experiments, spectroscopic analysis and theoretical calculations. The batch sorption showed that the removal percentage of phenol or naphthol on rGO in bisolute systems was significantly lower than those of phenol or naphthol in single-solute systems. However, the overall sorption capacity of rGO in bisolute system was higher than single-solute system, indicating that the rGO was a very suitable material for the simultaneous elimination of organic pollutants from aqueous solutions. The interaction mechanism was mainly pi-pi interactions and hydrogen bonds, which was evidenced by FTIR, Raman and theoretical calculation. FTIR and Raman showed that a blue shift of C=C and -OH stretching modes and the enhanced intensity ratios of I-D/I-G after phenols sorption. The theoretical calculation indicated that the total hydrogen bond numbers, diffusion constant and solvent accessible surface area of naphthol were higher than those of phenol, indicating higher sorption affinity of rGO for naphthol as compared to phenol. These findings were valuable for elucidating the interaction mechanisms between phenols and graphene-based materials, and provided an essential start in simultaneous removal of organics from wastewater.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-205457 (URN)10.1021/acs.est.6b06259 (DOI)000397477900019 ()28245121 (PubMedID)2-s2.0-85018522323 (Scopus ID)
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-05-22Bibliographically approved
Zou, Y., Wang, X., Ai, Y., Liu, Y., Li, J., Ji, Y. & Wang, X. (2016). Coagulation Behavior of Graphene Oxide on Nanocrystallined Mg/AI Layered Double Hydroxides: Batch Experimental and Theoretical Calculation Study. Environmental Science and Technology, 50(7), 3658-3667
Open this publication in new window or tab >>Coagulation Behavior of Graphene Oxide on Nanocrystallined Mg/AI Layered Double Hydroxides: Batch Experimental and Theoretical Calculation Study
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2016 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 7, p. 3658-3667Article in journal (Refereed) Published
Abstract [en]

Graphene oxide (GO) has attracted considerable attention because of its remarkable enhanced adsorption and multifunctional properties. However, the toxic properties of GO nanosheets released into the environment could lead to the instability of biological system. In aqueous phase, GO may interact with fine mineral particles, such as chloridion intercalated nanocrystallined Mg/Al layered double hydroxides (LDH-Cl) and nanocrystallined Mg/Al LDHs (LDH CO3), which are considered as coagulant molecules for the coagulation and removal of GO from aqueous solutions. Herein the coagulation of GO on LDHs were studied as a function of solution pH, ionic strength, contact time, temperature and coagulant concentration. The presence of LDH Cl and LDH-CO3 improved the coagulation of GO in solution efficiently, which was mainly attributed to the surface oxygen-containing functional groups of LDH Cl and LDH-CO3 occupying the binding sites of GO. The coagulation of GO by LDH-CI and LDH-CO3 was strongly dependent on pH and ionic strength. Results of coagulation of GO on LDHs was energetically favored by electrostatic interactions and hydrogen bonds, which was further evidenced by FTIR and XPS analysis. By integrating the experimental results, it was clear that LDH Cl could be potentially used as a cost-effective coagulant for the elimination of GO from aqueous solutions, which could efficiently decrease the potential toxicity of GO in the natural environment.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-185979 (URN)10.1021/acs.est.6b00255 (DOI)000373655800043 ()26978487 (PubMedID)2-s2.0-84964240157 (Scopus ID)
Note

QC 20160504

Available from: 2016-05-04 Created: 2016-04-29 Last updated: 2017-11-30Bibliographically approved
Ji, Y. & Luo, Y. (2016). New Mechanism for Photocatalytic Reduction of CO2 on the Anatase TiO2(101) Surface: The Essential Role of Oxygen Vacancy. Journal of the American Chemical Society, 138(49), 15896-15902
Open this publication in new window or tab >>New Mechanism for Photocatalytic Reduction of CO2 on the Anatase TiO2(101) Surface: The Essential Role of Oxygen Vacancy
2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 49, p. 15896-15902Article in journal (Refereed) Published
Abstract [en]

Photocatalytic reduction of CO2 into organic molecules is a very complicated and important reaction. Two possible pathways, the fast-hydrogenation (FH) path and the fast-deoxygenation (FdO) path, have been proposed on the most popular photocatalyst TiO2. We have carried out first-principles calculations to investigate both pathways on the perfect and defective anatase TiO2(101) surfaces to provide comprehensive understanding of the reaction mechanism. For the FH path, it is found that oxygen vacancy on defective surface can greatly lower the barrier of the deoxygenation processes, which makes it a more active site than the surface Ti. For the FdO path, our calculation suggests that it can not proceed on the perfect surface, nor can it proceed on the defective surface due to their unfavorable energetics. Based on the fact that the FH path can proceed both at the surface Ti site and the oxygen vacancy site, we have proposed a simple mechanism that is compatible with various experiments. It can properly rationalize the selectivity of the reaction and greatly simplify the picture of the reaction. The important role played by oxygen vacancy in the new mechanism is highlighted and a strategy for design of more efficient photocatalysts is proposed accordingly.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-199742 (URN)10.1021/jacs.6b05695 (DOI)000389962800025 ()2-s2.0-85006173288 (Scopus ID)
Note

QC 20170123

Available from: 2017-01-23 Created: 2017-01-16 Last updated: 2017-11-29Bibliographically approved
Chen, Z., Lu, J., Ai, Y., Ji, Y., Adschiri, T. & Wan, L. (2016). Ruthenium/Graphene-like Layered Carbon Composite as an Efficient Hydrogen Evolution Reaction Electrocatalyst. ACS Applied Materials and Interfaces, 8(51), 35132-35137
Open this publication in new window or tab >>Ruthenium/Graphene-like Layered Carbon Composite as an Efficient Hydrogen Evolution Reaction Electrocatalyst
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2016 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 51, p. 35132-35137Article in journal (Refereed) Published
Abstract [en]

Efficient water splitting through electrocatalysis has been studied extensively in modern energy devices, while the development of catalysts with activity and stability comparable to those of Pt is still a great challenge. In this work, we successfully developed a facile route to synthesize graphene-like layered carbon (GLC) from a layered silicate template. The obtained GLC has layered structure similar to that of the template and can be used as support to load ultrasmall Ru nanoparticles on it in supercritical water. The specific structure and surface properties of GLC enable Ru nanoparticles to disperse highly uniformly on it even at a large loading amount (62 wt %). When the novel Ru/GLC was used as catalyst on a glass carbon electrode for hydrogen evolution reaction (HER) in a 0.5 M H2SO4 solution, it exhibits an extremely low onset potential of only 3 mV and a small Tafel slope of 46 mV/decade. The outstanding performance proved that Ru/GLC is highly active catalyst for HER, comparable with transition-metal dichalcogenides or selenides. As the price of ruthenium is much lower than platinum, our study shows that Ru/GLC might be a promising candidate as an HER catalyst in future energy applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
graphene-like, ruthenium, supercritical fluid, electrocatalysis, hydrogen evolution reaction (HER)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-200757 (URN)10.1021/acsami.6b09331 (DOI)000391081700021 ()2-s2.0-85008199776 (Scopus ID)
Note

QC 20170209

Available from: 2017-02-09 Created: 2017-02-09 Last updated: 2017-11-29Bibliographically approved
Ding, X., Gao, Y., Fan, T., Ji, Y., Zhang, L., Yu, Z., . . . Sun, L. (2016). Silicon Compound Decorated Photoanode for Performance Enhanced Visible Light Driven Water Splitting. Electrochimica Acta, 215, 682-688
Open this publication in new window or tab >>Silicon Compound Decorated Photoanode for Performance Enhanced Visible Light Driven Water Splitting
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2016 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 215, p. 682-688Article in journal (Refereed) Published
Abstract [en]

An efficient dye (1) sensitized photoelectrochemical cell (DS-PEC) has been assembled with a silicon compound (3-chloropropyl) trimethoxy-silane (Si-Cl) decorated working electrode (WE) TiO2(1 + 2). The introduction of this Si-Cl molecule on photoanode leads to better performances on efficiency than untreated ones for light driven water splitting. The firm Si-O layer formed on TiO2 increased the resistance of the TiO2/catalyst interface which is assumed to decrease charge recombination from TiO2 to the oxidized catalyst 2. The work presented here provides an effective method to improve the performances of DS-PECs.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Dye-sensitized photoelectrochemical cell, photoanode, water splitting, molecular catalyst
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-194259 (URN)10.1016/j.electacta.2016.08.152 (DOI)000384008900077 ()2-s2.0-84984876979 (Scopus ID)
Note

QC 20161024

Available from: 2016-10-24 Created: 2016-10-21 Last updated: 2017-11-29Bibliographically approved
Yu, S., Wang, X., Ai, Y., Liang, Y., Ji, Y., Li, J., . . . Wang, X. (2016). Spectroscopic and theoretical studies on the counterion effect of Cu(II) ion and graphene oxide interaction with titanium dioxide. ENVIRONMENTAL SCIENCE-NANO, 3(6), 1361-1368
Open this publication in new window or tab >>Spectroscopic and theoretical studies on the counterion effect of Cu(II) ion and graphene oxide interaction with titanium dioxide
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2016 (English)In: ENVIRONMENTAL SCIENCE-NANO, ISSN 2051-8153, Vol. 3, no 6, p. 1361-1368Article in journal (Refereed) Published
Abstract [en]

With the widespread use of graphene oxide (GO), it is inevitable that part of GO is released into the environment and co-exist with heavy metal ions as contaminants and is likely to be co-adsorbed on minerals and oxides. This study, for the first time, demonstrates the individual and mutual removal mechanism of GO and Cu(II) on titanium dioxide (TiO2) by batch experiments, spectroscopic analysis and density functional theory (DFT) computations. Electrostatic interaction and hydrogen bonding are the dominant modes of GO sorption onto TiO2, and the interaction of Cu(II) with TiO2 is mainly dominated by inner-sphere surface complexation. The presence of Cu(II) enhances GO coagulation on TiO2 and vice versa. The experimental results are further verified by DFT sorption energy (Es) calculations in the order (TiO2-GO)-Cu > TiO2-GO for GO interaction and (TiO2-GO)-Cu > TiO2-Cu for Cu(II) interaction. The mutual interaction is favorable for the simultaneous removal of GO and heavy metal ions by surface complexation between Cu(II) and oxygen-containing functional groups. These findings might facilitate better understanding of the co-removal behavior of carbon nanomaterials and heavy metal ions on oxides, which is crucial to decreasing the environmental toxicity of pollutants in the natural environment.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-200792 (URN)10.1039/c6en00297h (DOI)000391423400013 ()2-s2.0-85000714773 (Scopus ID)
Note

QC 20170203

Available from: 2017-02-03 Created: 2017-02-02 Last updated: 2017-02-03Bibliographically approved
Ji, Y. & Luo, Y. (2016). Structure-dependent photocatalytic decomposition of formic acid on the anatase TiO2(101) surface and strategies to increase its reaction rate. Journal of Power Sources, 306, 208-212
Open this publication in new window or tab >>Structure-dependent photocatalytic decomposition of formic acid on the anatase TiO2(101) surface and strategies to increase its reaction rate
2016 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 306, p. 208-212Article in journal (Refereed) Published
Abstract [en]

Formic acid is a typical molecule that is involved in a lot important solar energy conversion processes. We perform first-principles calculations on the molecular mechanism of its photocatalytic decomposition reaction (PCD) on the anatase TiO2(101) surface. We find that the reaction barrier is sensitively dependent on the adsorption structure of the molecule. The one-step PCD of the monodentate formic acid has a lower barrier than that of bidentate formate. Coadsorbed water molecules can transform the formate from a bidentate to a monodentate configuration which greatly lower its decomposition barrier. Water molecule can also induce the spontaneous dissociation of the formic acid molecule. The monodentate dissociated formic acid is stabilized by the hydrogen bonds which will slightly enhance the barrier for its photodecomposition. However, the reaction rate can be further enhanced if the hydrogens are removed (for example, by oxygen molecules). Therefore, using coadsorbate and deliberately introducing and removing hydrogen bonds can be two strategies to tailor the photoreaction rate of the molecules.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
DFT, Hydrogen bond, Photocatalysis, Potential energy surface
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-180915 (URN)10.1016/j.jpowsour.2015.12.002 (DOI)000370309300024 ()2-s2.0-84950146817 (Scopus ID)
Funder
Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologySwedish Research Council
Note

QC 20160127. QC 20160319

Available from: 2016-01-27 Created: 2016-01-25 Last updated: 2017-11-30Bibliographically approved
Ji, Y. & Luo, Y. (2016). Theoretical Study on the Mechanism of Photoreduction of CO2 to CH4 on the Anatase TiO2(101) Surface. ACS Catalysis, 6(3), 2018-2025
Open this publication in new window or tab >>Theoretical Study on the Mechanism of Photoreduction of CO2 to CH4 on the Anatase TiO2(101) Surface
2016 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 3, p. 2018-2025Article in journal (Refereed) Published
Abstract [en]

Artificial photosynthesis of CO, has recently attracted intense attention as a potential solution for the energy crisis and global warming. However, the molecular mechanism of the reaction is quite complicated and is far from understood. We performed a first-principles calculation on the thermodynamically feasible formaldehyde pathway: CO2 -> HCOOH -> H2CO -> CH3OH -> CH4. The interconversion of the Cl molecules has been systematically investigated. We find that a two-electron process has a lower barrier than a one-electron process for the photoreduction of all of the molecules under investigation except for methanol. On the basis of the full potential energy surface for photoreduction of CO, to methane, the rate-limiting step is found to be the photoreduction of formic acid to formaldehyde, which contains the elementary step that has the largest kinetic barrier. It will be more efficient if CO instead of formic acid is the precursor of formaldehyde. Then the rate-limiting step becomes the photoreduction of CO, to CO. However, the barriers for the photoreduction of the organic molecules are all higher than the barriers for their photodecomposition reaction, which suggests that all of the Cl organic molecules are more easily oxidized than reduced. Thus, charge separation is crucial for improving the efficiency and selectivity of the reaction. The intertwining of photoreduction and photooxidation reactions might be one of the major reasons for the complexity and low efficiency of the reaction. On the basis of the calculations, a new mechanism for the reaction is proposed.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
artificial photosynthesis, TiO2, solar energy, density functional theory, potential energy surface
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-184536 (URN)10.1021/acscatal.5b02694 (DOI)000371755500072 ()2-s2.0-84960122862 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20160406

Available from: 2016-04-06 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
Cao, X., Ji, Y. & Luo, Y. (2015). Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst: Insight from First-Principles Calculations. The Journal of Physical Chemistry C, 119(2), 1016-1023
Open this publication in new window or tab >>Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst: Insight from First-Principles Calculations
2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 2, p. 1016-1023Article in journal (Refereed) Published
Abstract [en]

The catalytic properties of the single-Pd-doped Cu55 nanoparticle toward propane dehydrogenation have been systemically investigated by first-principles calculations, and the possible reaction mechanisms and effects of the single and multiple Pd doping on the catalytic activity have been discussed. Calculations reveal that the low-energy catalytic conversion of propane to propylene by the Pd/Cu single-atom catalyst comprises the initial crucial C–H bond breaking at either the methyl or methylene group, the facile diffusion of detached H atoms on the Cu surface, and the subsequent C–H bond dissociation activation of the adsorbed propyl species. The single-Pd-doped Cu55 nanoparticle shows remarkable activity toward C–H bond activation, and the presence of relatively inactive Cu surface is beneficial for the coupling and desorption of detached H atoms and can reduce side reactions such as deep dehydrogenation and C–C bond breaking. The single-Pd-doped Cu55 cluster bears good balance between the maximum use of the noble metal and the activity, and it may serve as a promising single-atom catalyst toward selective dehydrogenation of propane.

Keywords
Atoms, Calculations, Catalyst activity, Catalysts, Chemical activation, Dehydrogenation, Nanoparticles, Precious metals, Propane, Propylene, C-H bond dissociation, Catalytic conversion, Catalytic properties, CH-bond activation, Dehydrogenation of propanes, First-principles calculation, Propane dehydrogenation, Reaction mechanism
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-159882 (URN)10.1021/jp508625b (DOI)000348094000017 ()2-s2.0-84949115465 (Scopus ID)
Note

QC 20150211

Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2017-12-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6994-9802

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