Tantalum Cobalt Nitride Photocatalysts for Water Oxidation under Visible Light

Tantalum cobalt nitride photocatalysts were prepared using a simple drop coating method on a Ta foil substrate followed by thermal ammonia treatment, and their photoelectrochemical (PEC) properties for water oxidation under visible light were studied. The resulting Ta 0.9 Co 0.1 N x films showed a photocurrent of ca. 1.5 mA/cm 2 (12 times higher than that of Ta 3 N 5 ) under 100 mW/cm 2 visible light irradiation at 0.7 V vs Ag/AgCl in a 0.1 M Na 2 SO 4 aqueous solution (pH 11). The good PEC performance was attributed to the introduction of cobalt and the formation of cobalt nitride, which efficiently facilitates electron transfer and suppresses the recombination of photogenerated electron–hole pairs. Some cobalt nitride could further be oxidized to generate cobalt oxide, which serves as an efficient electrocatalyst for water oxidation. The enhanced visible light activity and film stability under light irradiation make tantalum cobalt nitride a promising semiconductor for PEC water oxidation.