Enhanced photocatalytic performance of direct Z-scheme Bi4Ti3O12/SrTiO3 photocatalysts for CO2 reduction to solar fuel

Abstract. Solar-driven CO2 reduction to solar fuel is an effective way to deal with the greenhouse effect and energy crisis. A one-step hydrothermal method was used to synthesize Bi4Ti3O12  /  SrTiO3 composite photocatalysts. The heterogeneous structure formed by intimate contact was observed between SrTiO3 (STO) nanoparticles and Bi4Ti3O12 (BTO) nanoplates, achieving an enhanced photocatalytic CO2 reduction yield of CO (13.37  μmol  /  g) that was 5.74-fold that of pure STO (2.33  μmol  /  g), with a high yield of CH4 (1.55  μmol  /  g). Characterizations of phase composition, morphology, and optical/electrochemical properties were applied to prove the heterojunction structure and its role in improving the photocatalytic performance. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy tests demonstrate that electrons transfer from STO to BTO and result in the generation of an internal electron field between the two phases. Consequently, a direct Z-scheme system was formed: photoelectrons in the conduction band of BTO transferred to the valence band of STO to recombine with the holes thus spatially separated the photogenerated electron–hole pairs while enabling the photocatalyst to achieve the maximum reduction and oxidation capability. The catalyst structure system proposed here may bring new ideas for the development of titanate-based photocatalysts with high CO2 reduction activity.