High-index facet engineering of PtCu cocatalysts for superior photocatalytic reduction of CO2 to CH4

Photocatalytic conversion of CO2 to CH4 is beneficial in alleviating global warming and advancing a low-carbon economy. However, it is a challenge to develop semiconductor-based photocatalysts with high CO2 conversion efficiency, resulting from electron-hole recombination in bulk semiconductors as well as the low adsorption and activation ability of stable CO2 molecules on the semiconductor surface. The combination of metal cocatalysts with semiconductors is a promising route to improve the photocatalytic performance in CO2 reduction. Herein, we demonstrate that the photocatalytic performance in the reduction of CO2 to CH4 can be greatly promoted by introducing high-index faceted cocatalysts. In this work, PtCu alloy concave nanocubes with (730) facets were loaded on C3N4 nanosheets, which act as cocatalysts greatly enhancing the photocatalytic activity and selectivity in CH4 production in comparison with (100) facet enclosed PtCu nanocubes. As revealed by experimental characterization combined with density functional theory calculations, the (730) high-index facet has more low-coordinated metal active sites to increase the adsorption and activation of CO2, while the introduction of Cu to Pt leads to synergistic effects between the two metals for high selectivity towards the desired CH4. This work highlights the rational facet design of cocatalysts for enhanced photocatalytic performance in CO2 conversion.