Palladium single atoms: engineering asymmetric active sites for selective photothermal reduction of carbon dioxide to methanol.

Photothermal (PT) synergistic catalysis for the conversion of CO2 to methanol (MeOH) represents a promising strategy for CO2 utilization. However, the development of Cu-ZnO catalysts exhibiting high thermal stability and photocatalytic activity remains a critical challenge for efficient CO2 conversion via the PT catalysis. To address these issues, Pd single atoms are successfully anchored onto the Cu-ZnO surface of the Z-scheme heterostructure (designated as Pd1/Cu-ZnO), resulting in three distinct asymmetric coordination environments: Pd-O-Cu, Pd-Cu, and Pd-O-Zn. The non-uniform charge distribution at the Pd-Cu site on Pd1/Cu-ZnO enhances the adsorption and dissociation of H2, while the Pd-O-Zn site simultaneously optimizes the CO2 adsorption configuration, thereby promoting significant elongation of the C=O bond. The band structures of semiconductors (CuO and ZnO) are modulated by Pd single atoms, which simultaneously enhances the localized surface plasmon resonance (LSPR) effect for Cu0, thereby improving Pd1/Cu-ZnO light response. The MeOH yield achieved with Pd1/Cu-ZnO as the catalyst is 1.45 times greater in the PT catalytic reaction compared to the thermal catalytic reaction, reaching 332.1 mmol·g-1Cu·h-1, while the selectivity increased from 50.1% to 87.2%, highlighting the exceptional performance of the single atom asymmetric sites. This study underscores the crucial role of single atoms in PT synergistic catalysis, demonstrating their superior potential for enhancing CO2 utilization under mild conditions and improving atomic economy.