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

Abstract

Solid solutions between SrTaO2N and CaTaO2N, i.e. Sr1-xCaxTaO2N (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 SrTaO2N and CaTaO2N. Apparent quantum efficiency as high as 1.67% at 420 ± 20 nm was achieved on Sr0.4Ca0.6TaO2N (x = 0.6) which stands as the highest one reported for SrTaO2N and CaTaO2N 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.