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

Abstract

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 H₂ 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 H₂ 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, C₃ N₄ -Pd₉ Cu₁ H_x (15 mg) achieves 100 % selectivity for CH₄ production with an average rate of 0.018 μmol h^-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.