Photo-induced charge separation and photocatalytic activity of Ga-doped SnO2

Ga-doped SnO₂ with different molar ratios of Ga/Sn (1, 2, 3, and 4 %) was prepared by a facile co-precipitation route. The photocatalysts prepared were characterized by N₂ adsorption–desorption measurements, X-ray diffraction, UV/Vis diffuse reflectance spectroscopy, and scanning electron microscope. The separation efficiency of photo-generated charge was studied using benzoquinone as scavenger. Hydroxyl radicals produced during photocatalytic process were detected by a terephthalic acid photoluminescence probing technique. Doping Ga³⁺ into SnO₂ can greatly enhance the separation efficiency of photo-induced charge and the formation rate of hydroxyl radicals. The superoxide radical is the main active species during the photocatalytic process. The catalytic activity of photocatalysts for decolorization of methyl orange in aqueous solution was investigated. Among the photocatalysts prepared, Ga-doped SnO₂ with 3 %Ga possesses the best photocatalytic activity and the underlying mechanism is suggested.