Defect-driven electroless deposition and activation of platinum sites on ZnIn2S4 nanosheets for accelerated kinetics of photocatalytic hydrogen production

The role of defects introduced into photocatalysts has been controversial, as some claim they serve as electron-trapping sites for improving the photogenerated charge separation, while others argue they act as exciton recombination centers to shorten the lifetime and mean free path of photocarriers. In the current study, we show the defect sites introduced into Zinc indium sulfide (ZIS) function as a double-bladed sword: on one hand, they act as recombination centers to impede photogenerated electron-hole separation in bulk ZIS; on the other hand, they drive electroless deposition and activation of the Pt co-catalyst through strong electronic coupling and thereby drastically enhance photocatalytic hydrogen production. As such, the defect-rich ZIS with a moderate Pt loading manifests the best hydrogen evolution rate of 15.56 mmol h−1 g−1 with a superb Pt-based TOF of 2334 h−1, apart from a high TON of 99610 in 92 h, which are among the best reported in literature for chalcogenide-based photocatalysts. Comprehensive microscopic, spectroscopic and photoelectrochemical characterizations unveil that the intimate coupling between the ZIS vacancy sites and deposited Pt atoms/clusters not only promotes photoexcited electron-hole separation, but also modulates local charge polarization to leverage the intrinsic activity of the co-catalyst.