Photoinduced Absorption Spectroscopy of Photoelectrocatalytic Methylene Blue Oxidation on Titania and Hematite: The Thermodynamic and Kinetic Impacts on Reaction Pathways

Author:

Guo Xinyue1,Ma Zixuan1ORCID,Yuan Yuling1ORCID,Kang Yan2,Xu Hong1,Mao Zhiping13ORCID,Ma Yimeng13ORCID

Affiliation:

1. Key Laboratory of Science and Technology of Eco‐Textile, Ministry of Education College of Chemistry and Chemical Engineering Donghua University Shanghai 201620 China

2. Shanghai Jahwa United Co., Ltd. Shanghai 200082 China

3. National Innovation Center of Advanced Dyeing & Finishing Technology Shandong Zhongkang Guochuang Research Institute of Advanced Dyeing & Finishing Technology Co., Ltd. Taian City Shandong Province 271000 China

Abstract

AbstractPhotoelectrochemical oxidation of methylene blue is investigated, with particular focus on the difference in kinetics and thermodynamics of decoloration and mineralization employing photoinduced absorption spectroscopy. Hematite and titania photoanodes are used for the comparison of both reactions, which is determined to be associated with the depth of the valence band (3.2 vs 2.5 V for titania and hematite, respectively). Methylene blue is mineralized by the titania photoanode, however it is only oxidized to small fragments by hematite. Such difference is related to the valence band potential that provides the thermodynamic driving force for photogenerated holes in both materials. In addition, the kinetic competition of water oxidation is found to occur on titania by controlling the pH of the electrolyte. In the pH 14 electrolyte, mineralization of methylene blue is suppressed due to the faster and dominant kinetics of water oxidation, in contrast to the complete mineralization in the near neutral electrolyte where water oxidation kinetics are modest. These results clearly address the importance considering both thermodynamic and kinetic challenges of methylene blue oxidation, which has been thought to be an easy molecule to oxidize, as the model reaction in the application of photo(electro)catalysis using metal oxides.

Funder

National Natural Science Foundation of China

Fundamental Research Funds for the Central Universities

Publisher

Wiley

Subject

General Physics and Astronomy,General Engineering,Biochemistry, Genetics and Molecular Biology (miscellaneous),General Materials Science,General Chemical Engineering,Medicine (miscellaneous)

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