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

Abstract

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.