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Significance of Hydroxyl Radical in Photoinduced Oxygen Evolution in Water on Monoclinic Bismuth Vanadate

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journal contribution
posted on 2017-11-07, 00:00 authored by Yukihiro Nakabayashi, Masami Nishikawa, Nobuo Saito, Chiaki Terashima, Akira Fujishima
Understanding the details of the mechanism of water photo-oxidation on monoclinic bismuth vanadate (m-BiVO4) is intriguing for efficient oxygen (O2) evolution under solar light. Hydroxyl (OH) radical was confirmed in a photocatalytic system of m-BiVO4 powders. OH radical is highly reactive to dimerize into hydrogen peroxide (H2O2), which is further oxidized into O2 molecule. Therefore, O2 evolution from OH radicals could be one of the plausible mechanisms. In the present study, to clarify the significance of O2 evolution from OH radicals, O2 molecules and OH radicals were generated by photoelectrochemical water oxidation on m-BiVO4 electrode. The amounts of O2 molecules and OH radicals were quantified by using an oxygen meter and a fluorescence probe method, respectively. The current efficiency of the photocurrent for the formation of OH radicals (∼0.06%) was much smaller than that for O2 evolution (∼100%), indicating that O2 evolution from OH radicals was not significant on m-BiVO4.

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