The present invention relates to a copper ion-modified tungsten oxide photocatalyst subjected to chemical etching treatment with a basic aqueous solution in which a rate of change in diffuse reflectance of the photocatalyst as measured at a wavelength of 700 nm between before and after irradiated with an ultraviolet light in atmospheric air is less than 10%; and a process for producing a copper ion-modified tungsten oxide photocatalyst which includes a copper ion modifying step of modifying a tungsten oxide powder with a copper ion; a chemical etching step of subjecting the tungsten oxide powder to chemical etching treatment with a basic aqueous solution, the chemical etching treatment being carried out either before or after the copper ion modifying step; and a drying step of drying the product obtained after the above steps at a temperature of 200° C. or lower.
展开▼
