Synergy of Palladium Nanoparticles and Single Atoms Promoted Tandem Reactions to Produce Hydroxyl Radical for Efficient Photoelectrochemical Water Purification.

Enhancing the highly selective photocatalytic generation of hydroxyl radical for water purification is extremely desirable but remains challenging since it normally requires a series of reactions associated with different catalysts. Here we report a synergistic catalyst (PdSAs+NPs/Vvac-BiVO4) with dual-functional active sites of palladium nanoparticles and single-atoms that are coordinatively responsible for the synthesis and decomposition of H2O2 in an optimized tandem reaction pathway. The application of this catalyst in the photoelectrochemical system can significantly enhance the production of H2O2 and •OH, with yields that are 531 and 3.5 times higher than its counterparts, respectively. Importantly, this catalyst can be applied for efficient water purification with superior performances including high catalytic activity and stability, wide applicability for different refractory pollutants, excellent performance in real-water systems, and good detoxification property. Physical, theoretical and in situ spectroscopy investigations show the crucial role of PdSAs+NPs/Vvac-BiVO4 catalyst, where the Pd nanoparticles promote the generation of H2O2 via O2 activation and further its desorption and migration to the nearby Pd single-atom sites via spillover, while the Pd single-atoms boost the catalytic decomposition of H2O2 to •OH. This study provides new insights into •OH production via the design of synergistic catalyst with dual-functional active sites for enhanced water purification.