Synthesis of Zinc Germanium Oxynitride Photocatalysts Using Solid Nitrogen Sources

ZnGeN 2 :ZnO, a solid solution of ZnGeN 2 and ZnO, functions as a photocatalyst active for overall water splitting under visible light. The absorption edge wavelength of ZnGeN 2 :ZnO shifts toward longer wavelength with increasing ZnO content. However, the conventional synthesis by nitridation under an NH 3 flow causes the reduction and volatilization of Zn species, which inherently restricts the maximum absorption edge wavelength to 460 nm. In this study, ZnGeN 2 :ZnO with a ZnO content of 66 mol% and an absorption edge of around 540 nm was synthesized using Zn 3 N 2 as a solid nitrogen source in a sealed evacuated tube. The obtained ZnGeN 2 :ZnO, when loaded with hydrogen and oxygen evolution cocatalysts, exhibited activity for overall water splitting under visible light irradiation. The photocatalytic activity was enhanced by post‐nitridation treatment. This work demonstrates a novel synthetic approach to long‐wavelength‐responsive ZnGeN 2 :ZnO and expands its potential for green hydrogen production via sunlight‐driven water splitting.