Ab Initio Calculation of Surface-Controlled Photocatalysis in Multiple-Phase BiVO4

Bismuth vanadate (BiVO4) is one of the semiconductors that are often used for photoelectrochemical water splitting because of its low band gap and various crystalline phases. Using density functional theory (DFT) based calculations, the surface properties, electronic structures, and photocatalytic properties of different facets are obtained. These include the (001), (011), and (101) facets that are truncated from ms-BiVO4 and the comparable {001}, {011}, and {101} facets that are produced by means of cleavage from ts-BiVO4. Our findings show a surface stability order of (001)/{001} > (101)/{101} > (011)/{011}. The (011) and {011} facets present distinct surface properties owing to the asymmetric a–b plane of ms-BiVO4, in contrast to ts-BiVO4. The work function of the {011} facet is dramatically decreased by 1 eV in comparison to the other facets, resulting from a positive surface dipole with an open lattice. Surface (001) shares geometric and electronic structure characteristics with {001}, and surface (101) possesses identical features with {101}. The electronic structures of surfaces (001)/{001} and (011) show indirect band gaps, while surfaces (101)/{101} possess direct band gaps. The mid-band gap states appear at surface {011} caused by the isolated O 2p states. For the photocatalytic properties, surfaces (001)/{001} have excellent visible-light absorption capacity and support H2O molecules to be adsorbed. Meanwhile, the flat-band potentials of (101)/{101} exhibit more negative behaviors than other surfaces. Our work indicates that surfaces (001)/{001} display outstanding photocatalytic performance, and surfaces (101)/{101} offer a promising and controllable potential for visible-light-driven photocatalytic activity. Surface (011) is perfectly suitable for the adsorption of the H2O molecule with constrained visible-light response. Moreover, the obtained surface–properties relationships provide comprehensive comparisons between the facets stemming from the two bulk phases. We confirm that the discrepancies between the (011) and {011} surfaces in facet morphologies and electronic structures are one of the reasons accounting for the distinct photoelectrochemical activities of ms- and ts-BiVO4 from experiments. Facet {011} can be exploited as a powerful photocatalyst if the mid-gap states are eliminated. We propose that regulating or decorating the exposed facets of ts-BiVO4 can be generalized to mitigate the differences between ms- and ts-BiVO4 in photoelectrochemical activities.