Triclinic-Phase Bismuth Chromate: A Promising Candidate for Photocatalytic Water Splitting with Broad Spectrum Ranges

Photocatalytic water splitting for solar energy conversion remains challenged by the lack of novel semiconductor photocatalysts with paramount parameters including wide light-harvesting ranges and suitable band structures. Here, a novel triclinic-phase bismuth chromate (Bi₂ CrO₆ ) acting as a semiconductor photocatalyst candidate is reported. Triclinic Bi₂ CrO₆ exhibits a broad absorption range of ≈650 nm with a direct bandgap of 1.86 eV and shows a suitable band structure for water splitting. Theoretical simulations of triclinic Bi₂ CrO₆ reveal a high charge mobility, possibly owing to the strong hybridized covalent bonds, large elastic modulus, and small carrier effective mass. The triclinic Bi₂ CrO₆ is demonstrated to work well toward photocatalytic water oxidation and hydrogen production reactions under visible light and match well with its absorption ranges. In particular, it exhibits decent photocatalytic water oxidation performance in the presence of various electron scavengers. Furthermore, the visible-light-driven Z-scheme overall water splitting system is fabricated by coupling triclinic Bi₂ CrO₆ as the oxygen evolution photocatalyst with SrTiO₃ :Rh as the hydrogen evolution photocatalyst, giving a stable overall water splitting with stoichiometric evolution of H₂ and O₂ . This work presents a promising semiconductor material enabling wide-range light harvesting for photocatalytic and photo-electrochemical solar energy conversion.