Continuous hydrogen generation from water was realized for 110 h using an n-type GaN film with a NiO cocatalyst. This GaN–NiO photocatalyst exhibits incident photon-to-current conversion efficiencies of 70 and 57% at wavelengths of 300 and 350 nm, respectively. These results indicate that the GaN–NiO photocatalyst has high stability and efficiency for hydrogen generation.

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We confirmed that GaN photocatalyst with NiO cocatalyst (GaN-NiO) continuously produced hydrogen from water for 500 hours without any extra bias. The GaN-NiO photocatalyst was hardly etched and 184-mL hydrogen gas was produced from the electric charge of 1612 coulombs, the Faradic efficiency of which was 89.2%. The conversion efficiency from incident light energy to hydrogen chemical energy was 0.98% in average for 500 h. The incident photon-to-current conversion efficiency (IPCE) was 50% at 300 nm and 35% at 350 nm after the experiment, which was much higher than those of other semiconductor-based photocatalysts.