Integration of Co Single Atoms and Ni Clusters on Defect-Rich ZrO 2 for Strong Photothermal Coupling Boosts Photocatalytic CO 2 Reduction.

We report a solvothermal method for the synthesis of an oxygen vacancy-enriched ZrO ₂ photocatalyst with Co single atoms and Ni clusters immobilized on the surface. This catalyst presents superior performance for the reduction of CO ₂ in H ₂ O vapor, with a CO yield reaching 663.84 μmol g ^-1 h ^-1 and a selectivity of 99.52%. The total solar-to-chemical energy conversion efficiency is up to 0.372‰, which is among the highest reported values. The success, on one hand, depends on the Co single atoms and Ni clusters for both extended spectrum absorption and serving as dual-active centers for CO ₂ reduction and H ₂ O dissociation, respectively; on the other hand, this is attributed to the enhanced photoelectric and thermal effect induced by concentrated solar irradiation. We demonstrate that an intermediate impurity state is formed by the hybridization of the d-orbital of single-atom Co with the molecular orbital of H ₂ O, enabling visible-light-driven excitation over the catalyst. In addition, Ni clusters play a crucial role in altering the adsorption configuration of CO ₂ , with the localized surface plasmon resonance effect enhancing the activation and dissociation of CO ₂ induced by visible-near-infrared light. This study provides valuable insights into the synergistic effect of the dual cocatalyst toward both efficient photothermal coupling and surface redox reactions for solar CO ₂ reduction.