Synergy between Palladium Single Atoms and Nanoparticles via Hydrogen Spillover for Enhancing CO2 Photoreduction to CH4

Selective photoreduction of carbon dioxide (CO2) into carbon-neutral fuels such as methane (CH4) is extremely desirable but remains a challenge since sluggish multiple proton-electron coupling transfer and various C-1 intermediates are involved. Herein, a synergistic function between single Pd atoms (Pd-1) and Pd nanoparticles (Pd-NPs) on graphitic carbon nitride (C3N4) for photocatalytic CO2 methanation is presented. The catalyst achieves a high selectivity of 97.8% for CH4 production with a yield of 20.3 mu mol g(cat.)(-1) h(-1) in pure water. Mechanistic studies revealed that Pd-1 sites activated CO2, while Pd-NPs sites boosted water (H2O) dissociation for increased H* coverage. The H* produced by Pd-NPs migrate to the Pd-1 sites to promote multiple proton-electron coupling transfer via hydrogen spillover. Moreover, the adjacent Pd-1 and Pd-NPs effectively stabilized intermediates such as *CHO, thereby favoring the pathway for CH4 production. This work provides a new perspective into the development of selective photocatalytic CO2 conversion through the artful design of synergistic catalytic sites.

Automated summary

This study demonstrates the synergistic function between single Pd atoms and Pd nanoparticles on graphitic carbon nitride for selective photocatalytic reduction of CO2 into CH4, providing a new perspective for the development of selective photocatalytic CO2 conversion.