New insight into photocatalytic CO2 conversion with nearly 100% CO selectivity by CuO-Pd/HxMoO3−y hybrids

Photocatalytic CO2 reduction holds promise for solving climate change. However, low conversion efficiency and low product selectivity limit current systems. Here, we report a strategy involving CuO-Pd deposited on HxMoO3−y with abundant oxygen vacancies (OVs) that drives CO2 photocatalytic reduction toward CO with nearly 100% selectivity and apparent quantum efficiency of 3.0% at 650 nm in H2O vapor at 100 °C. Detailed characterizations demonstrate that high performance mainly stems from the synergistic effect of the paired Cu-Pd sites in CuO-Pd and OVs in HxMoO3−y, where OVs serve as CO2 adsorption sites and induce the migration of localized electrons across the Schottky barrier to Cu-Pd sites, and then Cu-Pd sites promote CO2 reduction to CO. Theoretical calculation shows the strong hybridizations of Cu 3d - and Pd 3d - O 2p orbitals accelerate electrons transfer from CuO-Pd to CO2, effectively optimizing the rate-limiting step (CO2 * → COOH*).