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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, C3N4−Pd9Cu1Hx (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. Pick of the products: The photocatalytic reduction of CO2 to CH4, with a high production rate and complete selectivity is realized through the simultaneous incorporation of substitutional copper and interstitial hydrogen atoms into the lattice of palladium cocatalysts. The excellent performance can be explained by the synergistic interplay between Pd−H and Cu−CO sites in promoting the rate‐limiting reaction. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of CO 2 into CH 4 represents an appealing approach to alleviate the world's continued reliance on fossil fuels and global warming resulting from increasing CO 2 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 CO 2 to CH 4 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 CO 2 to CH 4 conversion: 1) Cu atoms provide catalytic sites to reduce CO 2 into CO and then to CH 4 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 CH 4 , which is the rate-limiting procedure in the conversion of CO 2 into CH 4 . Arising from the synergistic interplay between Pd-H and Cu-CO sites, C 3 N 4 -Pd 9 Cu 1 H x (15 mg) achieves 100 % selectivity for CH 4 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 CO 2 conversion through lattice engineering at atomic precision., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)