Synergistic effect of atomically dispersed Cu species and Ti-defects for boosting photocatalytic CO 2 reduction over hierarchical TiO 2 .

The photocatalytic water-mediated CO 2 reduction reaction, which holds great promise for the conversion of CO 2 into valuable chemicals, is often hindered by inefficient separation of photogenerated charges and a lack of suitable catalytic sites. Herein, we have developed a glycerol coordination assembly approach to precisely control the distribution of atomically dispersed Cu species by occupying Ti-defects and adjusting the ratio between Cu species and Ti-defects in a hierarchical TiO 2 . The optimal sample demonstrates a ∼4-fold improvement in CO 2 -to-CO conversion compared to normal TiO 2 nanoparticles. The high activity could be attributed to the Ti defects, which enhance the photogenerated charge separation and simultaneously facilitate the adsorption of water molecules, thereby promoting the water oxidation reaction. Moreover, by means of in situ EPR and FTIR spectra, we have demonstrated that Cu species can effectively capture photogenerated electrons and facilitate the adsorption of CO 2 , so as to catalyze the reduction of CO 2 . This work provides a strategy for the construction of atomic-level synergistic catalytic sites and the utilization of in situ techniques to reveal the underlying mechanism.