Water-activation-facilitated photocatalytic CO₂ reduction by a heterogeneous synergetic single-atomic Zn sites and Pd nanocrystals

Enhancing the photoreduction of carbon dioxide (CO₂) to produce valuable chemicals, such as carbon monoxide (CO), is of significant importance. The bottleneck in developing advanced catalysts lies in the rational design of catalytic centers with efficient CO₂ activation and hydrogen proton production. In this work, palladium nanoparticles (Pd NPs) were successfully modified on UiO-66-NH₂-Zn SAs (UN-Zn SAs) by a photo-deposition method. The optimized photocatalyst, 4 Pd NPs-UN-0.7Zn SAs, demonstrated exceptional performance in converting CO₂ to CO, exhibiting approximately 1.4-fold and 7.8-fold enhancements compared to UN-0.7Zn SAs and UN, respectively. A combination of time-resolved photoluminescence spectroscopy and electron paramagnetic resonance results unveiled that the introduction of Pd NPs effectively promoted the photogenerated charge separation and facilitated water activation to produce more hydrogen protons. The generated hydrogen protons were subsequently coupled with nearby CO₂ that was activated by Zn SAs, thus achieving the facile water-activation-induced CO₂ reduction process. Theoretical calculations further confirmed that the heterogeneous synergistic effects between Zn SAs and Pd NPs lowered the energy barrier for the rate-limiting step of CO₂ conversion to COOH*, thereby achieving efficient photocatalytic CO₂ reduction reactions. This work provides a new perspective on the development of efficient catalysts for the effective conversion of CO₂.