Efficient and stable photocatalytic hydrogen evolution from alkaline formaldehyde solution over Cd0.5Zn0.5S solid solution under visible light irradiation

Cd0.5Zn0.5S photocatalyst was prepared by a hydrothermal method and characterized by x-ray diffraction and UV–Vis absorption spectroscope techniques. Using the pollutant formaldehyde as an electron donor, the photocatalytic H2 evolution from water splitting under visible light (λ≥420 nm) irradiation was examined. It was found that formaldehyde can notably enhance photocatalytic H2 evolution with its simultaneous degradation. An alkaline condition also was beneficial to the photocatalytic H2 evolution. The effect of formaldehyde concentration on the H2 evolution rate was consistent with a Langmuir–Hinshelwood kinetic model. The stability test indicated that the catalyst was rather stable during 20-h irradiation and the average apparent quantum yield amounted to 3.1% under visible light irradiation (λ≥420 nm) and 25.7% at 420 nm even without any cocatalysts. The possible mechanism was discussed.