Noble-metal-free chalcogenide nanotwins for efficient and stable photocatalytic pure water splitting by surface phosphorization and cocatalyst modification

Chalcogenide photocatalysts are considered excellent candidates for photocatalytic water splitting because of their narrow bandgaps enabling utilization of visible light. However, severe self-oxidation of sulfide ions during water oxidation greatly restricts their application toward pure water splitting. Herein, we report the synthesis of a near-surface P-doped Cd0.5Zn0.5S (CZS) nanotwin photocatalyst, co-modified by red phosphorus (RP) and transition metal phosphides (TMPs, including FeP, Ni2P, and Co2P) by a one-step phosphorization method that enables efficient and stable pure water splitting. We demonstrate that homogenous phosphorus bridges formed from CZS to both RP and TMP because of near-surface P doping. These unique bridges enable effective charge transfer from RP to CZS and then to TMP via a two-electron Z-scheme mechanism. Significantly, the RP for photogenerated holes capture shows great corrosion–resistance during water oxidation, with simultaneous production of H2O2, while TMP promotes H2 evolution. The optimal CZS-P-Co2P shows a H2 evolution rate of 801.3 μmol/h/g for visible-light-driven pure water splitting, with an apparent quantum of 7.46% at 400 nm, which are among the highest reported values over chalcogenide photocatalysts. This work demonstrates the promising application potential of chalcogenides as photocatalysts for pure water splitting.