Metal oxynitrides are promising photocatalysts due to their narrow bandgap, but their lower stability compared to metal oxides is a drawback. The introduction of high-entropy alloys with entropy-stabilization features has shown high potential for various functional applications in recent years. By considering these two types of materials, we developed a high-entropy oxynitride for photocatalytic water splitting. The material, with a general composition of TiZrHfNbTaO6N3 and a d0 electronic configuration, showed a narrow bandgap of 1.6 eV, which is much lower than the bandgaps of relevant binary and high-entropy oxides. The material exhibited photocurrent generation and photocatalytic hydrogen production with high chemical stability, suggesting the high potential of high-entropy oxynitrides as advanced low-bandgap and stable photocatalysts.
