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.