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Improving the Photo-Oxidative Performance of Bi2MoO6 by Harnessing the Synergy between Spatial Charge Separation and Rational Co-Catalyst Deposition

Author:
Wu, Xuelian, Hart, Judy N., Wen, Xiaoming, Wang, Liang, Du, Yi, Dou, Shi Xue, Ng, Yun Hau, Amal, Rose, Scott, Jason
Source:
ACS applied materials & interfaces 2018 v.10 no.11 pp. 9342-9352
ISSN:
1944-8252
Subject:
bismuth, electrons, energy, gold, manganese oxides, materials science, molybdates, oxygen production, photocatalysis, photocatalysts, photooxidation, platinum, semiconductors, silver
Abstract:
It has been reported that photogenerated electrons and holes can be directed toward specific crystal facets of a semiconductor particle, which is believed to arise from the differences in their surface electronic structures, suggesting that different facets can act as either photoreduction or photo-oxidation sites. This study examines the propensity for this effect to occur in faceted, plate-like bismuth molybdate (Bi₂MoO₆), which is a useful photocatalyst for water oxidation. Photoexcited electrons and holes are shown to be spatially separated toward the {100} and {001}/{010} facets of Bi₂MoO₆, respectively, by facet-dependent photodeposition of noble metals (Pt, Au, and Ag) and metal oxides (PbO₂, MnOₓ, and CoOₓ). Theoretical calculations revealed that differences in energy levels between the conduction bands and valence bands of the {100} and {001}/{010} facets can contribute to electrons and holes being drawn to different surfaces of the plate-like Bi₂MoO₆. Utilizing this knowledge, the photo-oxidative capability of Bi₂MoO₆ was improved by adding an efficient water oxidation co-catalyst, CoOₓ, to the system, whereby the extent of enhancement was shown to be governed by the co-catalyst location. A greater oxygen evolution occurred when CoOₓ was selectively deposited on the hole-rich {001}/{010} facets of Bi₂MoO₆ compared to when CoOₓ was randomly located across all of the facets. The elevated performance exhibited for the selectively loaded CoOₓ/Bi₂MoO₆ was ascribed to the greater opportunity for hole trapping by the co-catalyst being accentuated over other potentially detrimental effects, such as the co-catalyst acting as a recombination medium and/or covering reactive sites. The results indicate that harnessing the synergy between the spatial charge separation and the co-catalyst location on the appropriate facets of plate-like Bi₂MoO₆ can promote its photocatalytic activity.
Agid:
5952816