Metal Oxide Semiconductor Materials for Photo-oxidation of Water and Organic Amine Groups.

Photoelectrochemical water oxidation;Electrochemical impedance spectroscopy study on metal oxide for water oxidation;Photoelectrochemical water splitting;Copper tungstate (CuWO4);Alpha tin tungstate (SnWO4);Electrode construction with the use of graphene;Chemistry;Science;Chemistry

Pyper, Kayla J.Pecoraro, Vincent L. ;

University of Michigan

关键词: Photoelectrochemical water oxidation;    Electrochemical impedance spectroscopy study on metal oxide for water oxidation;    Photoelectrochemical water splitting;    Copper tungstate (CuWO4);    Alpha tin tungstate (SnWO4);    Electrode construction with the use of graphene;    Chemistry;    Science;    Chemistry;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/113412/kpyper_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

With environmental decline due to increasing carbon dioxide and pollution levels, sustainability and ecofriendly improvements are necessary to maintain quality of life. In order to move in this direction, new sources of energy must be identified and sustainable methods must be realized. The overarching themes of sustainable energy addressed in this thesis are developing clean fuel, advancing energy efficiency, and advancing clean energy. These themes lend toward removal of our current reliance on unclean sources like oil and coal, and useless nonrenewables, toxic substances, and chemical waste. The future energy source we chose to focus on is hydrogen by photoelectrochemical water splitting using metal oxide semiconductors and visible sunlight. To advance clean energy we have chosen to focus on a greener approach to organic oxidations, specifically amine oxidation, by use of a semiconductor metal oxide and visible sunlight. With a Z-scheme approach for water splitting the central material focused on this work is copper tungstate, an n-type visible- light absorbing semiconductor, for the water oxidation half reaction. An emphasis is also placed on the use of copper tungstate to provide sustainable pathways for organic amine oxidation reactions. Another n-type material from the tungstate family, alpha tin tungstate, was also synthesized and explored for sustainable water oxidation.Copper tungstate was evaluated for mechanistic insight into water oxidation under visible-light illumination using electrochemical impedance spectroscopy (EIS). A mid-gap energy state (rather than the valence band) was identified as the carrier source in the water oxidation reaction on the surface of polycrystalline sol-gel copper tungstate electrodes. This state is likely composed of Cu(3d) character. The best way to improve materials for water oxidation is to identify more in depth information on how the reaction takes place on the material surface. These EIS studies on copper tungstate have provided us with chemical information to improve the reactivity of copper tungstate. It has also expanded the scope to a subset of organic reactions potentially catalyzed by these Cu 2+ sites with orbital energies within the band gap. Copper tungstate performs benzylamine oxidation to benzylidenebenzylimine with 89% Faradic efficiency, which was confirmed by gas chromatography.