Atomically dispersed Ni-P4 active sites on few-layer violet phosphorene for efficient photocatalytic hydrogen evolution

Single-atom catalysts (SACs) are currently one of the most active forefronts in heterogeneous catalysis. The vast majority of SACs are coordinated by highly electronegative heteroatoms like N and O, which often results in electron-deficient SACs and undesirable catalytic performance. Tuning the coordination environment of SACs by low-electronegativity species is essential, yet to date remains largely unexplored. Here, few-layer violet phosphorene (VP) was used as a giant phosphorus ligand to confine Ni single-atoms via a photoreduction approach. Combined experimental analysis and density-functional theory calculations confirmed that VP nanosheets covalently stabilized monovalent Ni (I) single-atoms in a Ni-P4 atomic configuration. The active and durable Ni-P4 moieties were shown to reduce the work function and band gap, optimize proton adsorption, and facilitate photoexcited charge separation, synergistically leading to a maximal hydrogen evolution rate of 377.8 μmol h−1g−1 which is an 11-fold increase than that of VP nanosheets. This work paves an avenue for the exploration of VP’s enormous potential in solar-driven artificial photosynthesis as well as provides guidance to the rational design of P-coordinated SACs for diverse applications beyond water splitting.