A surface-alkalinized Ti3C2 MXene as an efficient cocatalyst for enhanced photocatalytic CO2 reduction over ZnO

Photocatalytic reduction of carbon dioxide (CO2) into hydrocarbon fuels has attracted increasing research attention in recent years. However, the fast recombination of photoinduced charge carriers and poor adsorption/activation capability of CO2 molecules limit the photoconversion efficiency. Herein, we report on loading a two-dimensional (2D) titanium carbide (Ti3C2) MXene as a noble-metal-free cocatalyst onto zinc oxide (ZnO) via a facile electrostatic self-assembly method for efficient CO2 photoreduction. It is interesting to find that the ZnO loaded with 7.5 wt% of surface-alkalinized Ti3C2 exhibited remarkably improved evolution rates of CO (30.30 mu mol g(-1) h(-1)) and CH4 (20.33 mu mol g(-1) h(-1)), which were approximately 7-fold and 35-fold those of bare ZnO, respectively. The surface-alkalinized Ti3C2 MXene is believed to play a crucial role in improving the separation/transfer of photoinduced charge carriers and the adsorption/activation of CO2 molecules, accounting for the superior photocatalytic activity of CO2 reduction. Our work demonstrates that the Ti3C2 MXene could be employed as a noble-metal-free cocatalyst for efficient photocatalytic CO2 reduction.