Black single-crystal TiO2 nanosheet array films with oxygen vacancy on {001} facets for boosting photocatalytic CO2 reduction

Abstract

• Preparation of black TiO 2 by a mild aluminothermic reduction. • Oxygen vacancy doping can extend the light absorption range of TiO 2 to the visible light region. • The black TiO 2 with oxygen vacancy on {001} facets has the best photocatalytic CO 2 reduction activity. Black TiO 2 nanosheet array films with oxygen vacancy on {001} facets were prepared by solid phase reaction with a mild aluminothermic reduction method. The oxygen vacancies increase the absorption of visible light and the separation efficiency of photogenerated electron-hole pairs. For the black TiO 2 with oxygen vacancy prepared by annealing, only the oxygen vacancies on {001} facets boost the photocatalytic CO 2 reduction, while these on {101} facets in a small number increase the recombination of photogenerated electrons and holes and inhibit the photocatalytic CO 2 reduction performance. Meanwhile, the black TiO 2 nanosheet array films with oxygen vacancy on {001} facets have a good photocatalytic CO 2 reduction to CO with a reduction rate of 128.5 µmol•g –1 •h –1 under visible light irradiation, which is ascribed to the formation of oxygen vacancy and the synergistic effect of special unsaturated coordination Ti 5c atom improving the adsorption capacity of CO 2 and increasing the reduction rate of CO 2 to CO.