Single Pd atoms synergistically manipulating charge polarization and active sites for simultaneously photocatalytic hydrogen production and oxidation of benzylamine

Photocatalytic hydrogen production coupled with selective oxidation of organic substances is of significance and remains a grand challenge because of unsatisfied photocatalytic activity and unclear mechanism. Herein, we first design and synthesize atomically dispersed Pd on ZnIn2S4 (PdSA-ZIS) for simultaneously photocatalytic hydrogen production and oxidation of benzylamine. Based on systematic characterization with a combination of theoretical simulations, light irradiation-kelvin probe force microscopy (KPFM) and time-resolved photoluminescence spectrum etc, we demonstrate that Pd single atoms can modulate charge polarization as well as the active sites of ZnIn2S4 to promote spatial charge separation and decrease the energy barriers of reaction. The electrons are enriched around Pd single atoms-ZnS layer with lowest energy barriers of H2 production, while more holes are accumulated on InS2 layer for dehydrogenation of benzylamine. This enables PdSA-ZIS to exhibit remarkable photocatalytic performance for the co-production of N-benzylidenebenzylamine (10.2 mmol g−1 h−1) with selectivity of 100% and H2 (11.1 mmol g−1 h−1) under visible irradiation. Furthermore, by means of controlled experiments, theoretical simulations and in situ electron spin resonance (ESR) spectroscopy, a synergetic photocatalytic redox mechanism on the Pd single atom-ZIS interface for dehydrogenation and coupling of benzylamine and H2 production has been investigated in detail.