SrTaO2N-CaTaO2N solid solutions as efficient visible light active photocatalysts for water oxidation and reduction

Solid solutions between SrTaO 2 N and CaTaO 2 N, i.e. Sr 1-x Ca x TaO 2 N (0.0 ≤ x ≤ 1.0) were synthesized and investigated as photocatalysts for water oxidation and reduction. A wealth of important parameters such as Ta-(O, N) bond length, Ta-(O, N)-Ta bond angle, band gap and band edge positions can be successively tuned by varying Sr/Ca molar ratios at A site. These solid solutions work well as photocatalysts to drive water splitting reactions under visible light illumination which clearly outperform their parent compounds SrTaO 2 N and CaTaO 2 N. Apparent quantum efficiency as high as 1.67% at 420 ± 20 nm was achieved on Sr 0.4 Ca 0.6 TaO 2 N (x = 0.6) which stands as the highest one reported for SrTaO 2 N and CaTaO 2 N to date. This simple approach by cation control at A site serves as a useful tool to tailor photocatalytic properties of perovskite oxynitrides, opening new playgrounds for the design and development of these tempting compounds as efficient photocatalysts.