Bismuth Tantalum Oxyhalogen: A Promising Candidate Photocatalyst for Solar Water Splitting

As wide range of light absorption and suitable redox potentials are prerequisites for photocatalytic water splitting, exploring new semiconductor-based materials with proper band structures for water splitting still calls for long-standing efforts. In this work, a series of photocatalysts, bismuth tantalum oxyhalide, Bi4TaO8X (X = Cl, Br), with valence band and conduction band positions at approximate to-0.70 and approximate to 1.80 eV versus the reversible hydrogen electrode (RHE), respectively, are found to be capable for both water oxidation and reduction under visible light irradiation. Using flux synthetic methods, Bi4TaO8X (X = Cl, Br) with microplatelet morphology can be successfully prepared. The photocatalyst based on these materials shows an apparent quantum efficiency as high as 20% at 420 nm for water oxidation. In addition, a Z-scheme system coupling Bi4TaO8Br with Ru/SrTiO3:Rh is successfully achieved for overall water splitting with a stoichiometric ratio of H-2 and O-2 evolutions. This work demonstrates a new series of semiconductors Bi4TaO8X (X = Cl, Br) with the promising application in the field of solar energy utilization.