High‐Entropy Design Boosts Visible‐Light‐Induced Photocatalytic Hydrogen Production on Perovskite Oxynitrides

Abstract Semiconducting oxynitrides are attractive candidates for producing solar hydrogen, while the abundant defects evolved during harsh nitridation synthesis and the unfavorable charge transfer properties of oxynitrides restrict the solar‐to‐hydrogen conversion. Herein, by virtue of high‐entropy design, a single‐phase high‐entropy oxynitride {LaSmPrNdGd}TiO 2 N (HE‐LnTiO 2 N) is presented toward alleviating these issues for the first time. It is found that the HE‐LnTiO 2 N can be obtained at milder nitridation conditions than those of the conventional one‐element oxynitrides, which is beneficial to inhibiting the formation of reduced Ti 3+ defects that act as recombination centers. Moreover, the combined contribution of the multiple lanthanide elements modifies the electronic structures of HE‐LnTiO 2 N, thus enhancing the charge transfer efficiency. Consequently, the photocatalytic hydrogen evolution activity achieved on HE‐LnTiO 2 N is two times that of the representative one‐element oxynitride SmTiO 2 N under visible light irradiation. This study highlights the efficacy and great potential of high‐entropy design toward optimizing photocatalytic materials for enhanced solar energy conversion.