Lattice Engineering on Metal Cocatalysts for Enhanced Photocatalytic Reduction of CO2 into CH4

Photocatalytic conversion of CO2 into CH4 represents an appealing approach to alleviate the world's continued reliance on fossil fuels and global warming resulting from increasing CO2 concentrations in the atmosphere. However, its practical application is greatly limited by serious electron-hole recombination in the photocatalysts and the production of CO and H-2 as side reactions. Herein, for the first time, it is demonstrated that the photocatalytic reduction of CO2 to CH4 can be significantly improved through the simultaneous alloying and hydriding of metal cocatalysts. The isolation of Cu and H atoms in Pd lattices play three roles in the enhancement of CO2 to CH4 conversion: 1) Cu atoms provide catalytic sites to reduce CO2 into CO and then to CH4 to suppress H-2 evolution; 2) H atoms improve the electron-trapping ability of cocatalysts; and 3) H atoms accelerate the reduction of CO to CH4, which is the rate-limiting procedure in the conversion of CO2 into CH4. Arising from the synergistic interplay between Pd-H and Cu-CO sites, C3N4-Pd9Cu1Hx (15 mg) achieves 100% selectivity for CH4 production with an average rate of 0.018 mu molh(-1) under visible-light irradiation. This work provides insights into the design of a cocatalyst for highly selective CO2 conversion through lattice engineering at atomic precision.