Preparation of visible-light-responsive photocatalyst by dehydronitrization of gallium oxide hydroxide for hydrogen evolution from water

Abstract We have performed dehydronitrization of GaOOH under NH 3 flow to produce nitrogen doped Ga 2 O 3 and examined their photocatalytic activities for H 2 evolution from an aqueous methanol solution under visible light irradiation. GaOOH was synthesized by hydrothermal treatment and dehydronitrided at a temperature ranging from 773 K to 1273 K under NH 3 flow. At first, GaOOH was dehydrided to Ga 2 O 3 under 873 K and followed nitrization. With increasing dehydronitrization temperature, the products were getting closer to full nitride (GaN). Among all dehydronitrided samples, only one sample sintered at 1173 K showed photocatalytic activity under visible light irradiation and its crystalline structure had not changed before and after the reactions, while other samples did not show the activity and were oxidized to GaOOH. From thermodynamical aspect, if nitrogen dissolved into oxide or making oxynitride, its chemical potential must be lower than that of N in GaN. Therefore, there should be some gallium oxinitride phase like GaN y O 3-x stable in water showing photocatalytic activity.