Efficient photocatalytic hydrogen evolution through reverse hydrogen spillover on photoactivated copper-doped mesoporous titania spheres

Transition-metal-doped mesoporous TiO2 (M-mTiO2) spheres are highly desired for photocatalysis because of their large specific surface area and extended light absorption. Herein, a universal method is developed for the preparation of M-mTiO2 spheres and their photocatalytic mechanism is unveiled. Fe-mTiO2, Co-mTiO2, Ni-mTiO2, Cu-mTiO2 spheres are successfully prepared by the developed method. Among all M-mTiO2 samples, the Cu-mTiO2 catalyst exhibits reversible photoactivation phenomenon during photocatalysis. The photocatalytic hydrogen evolution rate on photoactivated Cu-mTiO2 can reach 3.31 mmol g−1 h−1, which is much higher than those of other M-mTiO2 and is 28.3 times of that of the mTiO2. Density functional theory (DFT) calculations reveal that the photoactivation of Cu-mTiO2 is associated with the facile formation of oxygen vacancies on Cu-mTiO2. The photoactivation induces the active site change and the light absorption increase of Cu-mTiO2. The active site change has the dominant role for the enhancement of photocatalytic performance. On the photoactivated Cu-mTiO2, the hydrogen production is through a reverse hydrogen spillover process. Our findings not only provide a universal method for the preparation of M-mTiO2 but also deepen the understanding about the photoactivation and the hydrogen production mechanism.