Modulating Ti t2g Orbital Occupancy in a Cu/TiO2 Composite for Selective Photocatalytic CO2 Reduction to CO.

The electronic structure of composites plays a critical role in photocatalytic conversion, whereas it is challenging to modulate the orbital for an efficient catalyst. Herein, we regulated the t2g orbital occupancy state of Ti to realize efficient CO2 conversion by adjusting the amount of photo-deposited Cu in the Cu/TiO2 composite. For the optimal sample, considerable electrons transfer from the Cu d orbital to the Ti t2g orbital, as proven by X-ray absorption spectroscopy. The Raman spectra results also corroborate the electron enrichment on the Ti t2g orbital. Further theoretical calculations suggested that the orbital energy of the Ti 3d orbital in TiO2 is declined, contributing to accepting Cu 3d electrons. As a result, the Cu/TiO2 composite exhibited an extremely high selectivity of 95.9 % for CO, and the productivity was 15.27 µmol g-1 h-1 , which is almost 6 times that of the original TiO2 . Our work provides a strategy for designing efficient photocatalysis as a function of orbital regulation.