Enhanced photocatalytic CO2 reduction to methanol by modulating valence states of copper in CuSrTiO3

Manipulating the oxidation states of transition metals is an ideal solution to achieve selective generation of different products and copper is widely used in CO 2 photocatalytic reduction to methanol. However, the understanding on the effects of valence states of copper species in SrTiO 3 on its structure and the selectivity of the corresponding product in CO 2 photocatalysis are currently still limited. Here, copper-doped SrTiO 3 nanofibers with different controllable ratios of Cu + /Cu 2+ and Cu + /Cu 0 were prepared by the combination of the electrospinning with the in-situ reduction method. The proportion of copper with different valence states (Cu + /Cu 2+ and Cu + /Cu 0 ) was changed by rationally adjusting the time of hydrogen reduction. The presence of monovalent copper facilitated the generation of reactive intermediates, thereby enhancing its photocatalytic activity. The copper-doped SrTiO 3 nanofibers obtained after 3 h of hydrogen reduction (STCu 0.08 -H-3 h) had the highest proportion of Cu + /Cu 2+ and Cu + /Cu 0 with the highest methanol yield (6.96 μmol·g −1 ·h −1 ). Methanol generation rate and Cu + /Cu 2+ ratio of STCu 0.08 -H-xh (x = 1, 2, 3, 4,5) with different hydrogen reduction time were proven to be linearly positively correlated. Furthermore, theoretical investigation and in-situ CO 2 infrared spectrum deeply understood the difference of CO 2 adsorption behavior and CO 2 activation over Cu 2+ and Cu + of STCu 0.08 -H-3 h photocatalyst and the reaction intermediates involved in the photocatalytic CO 2 reduction to methanol.