Coupling Cu Single Atoms and Phase Junction for Photocatalytic CO2 Reduction with 100% CO Selectivity

Reducing CO2 through artificial photosynthesis is a remarkable strategy for converting solar energy into useful chemical feedstocks. However, most photocatalytic systems suffer from low efficiency owing to insufficient active sites and the lack of a directional charge-transfer channel. Herein, we develop Cu single atoms (SAs) on the nitrogen-doped carbon anchored on TiO2 with the anatase–rutile mixed phase (Cu SAs/TiO2), which shows 100% CO selectivity and high apparent quantum efficiency of 2.0% at 420 nm in photocatalytic CO2 reduction with H2O vapor. Such a high performance is ascribed to the synergetic effect of Cu SAs and phase junction, where Cu SAs act as adsorption and activation sites of CO2 and phase junction accelerates the migration of photogenerated electrons along the Ti–N–Cu–(O–CO2) channel. Theoretical calculation further shows that the strong hybridization of Cu 3d and CO2–O 2p orbitals promotes the electron transfer from Cu SAs to CO2, effectively optimizing the rate-limiting step (CO2* → COOH*).