Synthesis of BaTaO2N oxynitride from Ba-rich oxide precursor for construction of visible-light-driven Z-scheme overall water splitting

Barium tantalum oxynitride (BaTaO 2 N) with an absorption edge of ca. 660 nm is one of the most promising photocatalysts for solar water splitting, and is usually synthesized by nitriding a mixture of Ba and Ta-containing compounds with a Ba/Ta molar ratio of unity under ammonia flow at high temperature, usually causing a high density of defect sites. Herein, we introduce a novel synthesis method for BaTaO 2 N (BTON) by employing Ba-rich LiBa 4 Ta 3 O 12 , prepared by a flux method, as a precursor of nitridation. As a comparison, BaTaO x was prepared by conventional solid state reaction and used as the precursor. The as-nitrided samples were correspondingly denoted as BTON-Flux and BTON-SSR. It was found that well-crystallized BTON oxynitride can be similarly obtained by both methods, but the BTON-Flux sample exhibits significantly decreased defect density and enhanced surface area relative to the BTON-SSR sample. As a result of their structural differences, the photocatalytic water splitting performance of the BTON-Flux sample, regardless of the H 2 -evolving half reaction in the presence of methanol or Z-scheme overall water splitting, is much better than that of BTON-SSR. This study may open up a novel strategy for preparing oxynitride photocatalyst with decreased defect density for the promotion of solar water splitting. A novel synthesis of BaTaO 2 N photocatalyst with low defect density is introduced for promotion of overall water splitting performance.