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 evolution from water splitting under visible light () irradiation was examined. It was found that formaldehyde can notably enhance photocatalytic evolution with its simultaneous degradation. An alkaline condition also was beneficial to the photocatalytic evolution. The effect of formaldehyde concentration on the 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 () and 25.7% at 420 nm even without any cocatalysts. The possible mechanism was discussed.