Mixed-valence Palladium Single-Atom Catalyst Induced by Hybrid TiO2-graphene Through a Photochemical Strategy

Heterogeneous Pd single-atom catalysts (Pd SACs) have demonstrated high efficiency in C-C coupling reactions, which are considered the cornerstones of organic synthesis. However, the development of 2D materials for the evaluation of the catalytic efficiency of mixed-valence Pd SACs remains a significant challenge. In this study, we prepared various mixed-valence Pd SACs via photodeposition. The electronic structure and dispersion state of the surface Pd species were confirmed. The important role of graphene oxide in the design of atomically dispersed Pd species was further confirmed through comparative experiments with Pd/TiO2. The mixed-valence Pd SACs exhibited excellent catalytic activity for the typical palladium-catalyzed Suzuki and Sonogashira C-C coupling. Theoretical calculations and EXAFS spectra were used to determine the mechanism for tailoring the Pd0/Pd2+ atomic ratios. These studies initiate a broad portfolio of mixed-valence metal-based single-atom catalysts (SACs).