Significant CO2 photoreduction on a high-entropy oxynitride

CO2 photoreduction on photocatalysts is a nature-friendly solution to decrease the CO2 amount, but the method still has low efficiency because of difficult separation and easy recombination of charge carriers in available catalysts. In this study, a high-entropy oxynitride was introduced as an active photocatalyst for photoreduction. The material had a chemical composition of TiZrNbHfTaO6N3 and was produced by a high-pressure torsion method followed by oxidation and nitriding. It showed higher photocatalytic CO2 to CO conversion compared to corresponding high-entropy oxide, benchmark photocatalyst P25 TiO2, and almost all catalysts introduced in the literature. The high activity of this oxynitride, which also showed good chemical stability, was attributed to the large absorbance of light and easy separation of electrons and holes, the low recombination of charge carriers, and the high CO2 adsorption on the surface. These findings introduce high-entropy oxynitrides as promising photocatalysts for CO2 photoreduction.