The Dependence of Bi₂MoO₆ Photocatalytic Water Oxidation Capability on Crystal Facet Engineering

Crystal facet engineering of semiconductor photocatalysts is regarded as an emerging strategy to tune their physicochemical properties and optimize the photoreactivity of the materials. In this work, two plate-like Bi₂MoO₆ samples were prepared, dominant in either the distinctly different {100} or {010} facets. As a consequence of the electronic structure effects induced by the facets, the {100}-dominant Bi₂MoO₆ (100-BMO) possessed a smaller band gap and delivered a much higher photocatalytic water oxidation activity than {010}-dominant Bi₂MoO₆ (010-BMO). A greater charge carrier density in 100-BMO was found to promote electron accumulation on the {100} surfaces, leading to the narrower band gap, as supported by Mott-Schottky measurements. Efficient intrinsic electron-hole separation and longer charge carrier lifetimes in 100-BMO were also observed. Further, a higher photocurrent density and smaller Nyquist plot arc radius presented by 100-BMO imply a higher charge transfer capacity. EPR analysis indicated that the 100-BMO boasted a higher oxygen vacancy density, whereby the vacancies could serve as shallow donors to trap electrons and suppress photogenerated electron-hole pair recombination. Overall, the {100} facet in Bi₂MoO₆ delivered a mix of distinctly advantageous characteristics relative to the {010} facet with the findings clearly illustrating the value of crystal facet engineering in boosting photocatalytic performance.