High-performance of Cu-TiO2 for photocatalytic oxidation of formaldehyde under visible light and the mechanism study

Photocatalysis is regarded as a promising method for indoor formaldehyde (HCHO) removal, and there remains a strong demand for the development of highly efficient photocatalysts for HCHO oxidation under visible light. Herein, by grafting nano CuOx clusters onto TiO2, the higher performance is achieved over Cu-TiO2 for the photocatalytic oxidation of HCHO under visible light compared with the typical photocatalysts N-TiO2 and g-C3N4. It is found that the presence of water greatly promotes the activity of HCHO oxidation on Cu-TiO2. The characterization results indicate that the CuOx clusters on TiO2 exhibit high redox reversibility between Cu (II) and Cu (I) and greatly facilitate the migration of electrons. The mechanism of photocatalytic oxidation of HCHO was explored by using in situ DRIFTS measurements and DFT calculations. It is shown that HCHO is firstly oxidized to dioxymethylene (DOM), and then DOM is transformed into formate species under visible light irradiation. DFT calculations results indicate that the OH species are responsible for surface formate decomposition, which is the rate-determining step, while O2− radical is not active in formate decomposition. Our findings improve the understanding on the photocatalytic oxidation of HCHO, and the Cu-TiO2 catalyst is a promising candidate for practical application in indoor air purification.