Tunable interfacial charge transfer in a nickel sulfide/red phosphorus composite for efficient benzyl alcohol selective oxidation: Effect of nickel sulfide crystal phase.

Red phosphorus (RP) has recently attracted considerable attention in the field of photocatalysis owing to its remarkable optical properties. However, the rapid recombination of photogenerated carriers presents a substantial challenge for the application of RP in the selective photocatalytic oxidation of benzyl alcohol. Herein, a series of nickel sulfide (NiS) materials with different crystal phase, including α-NiS, β-NiS and α-β-NiS, were employed to modulate the interfacial charge transfer in RP for photocatalytic oxidation of benzyl alcohol (BA) coupled with H2 evolution. A comprehensive array of experimental and theoretical analyses has demonstrated that the Ohmic junction formed between β-NiS and RP is more conducive to enhancing the separation and migration of carriers in comparison to the Schottky junction formed between α-NiS and RP. As expected, the β-NiS/RP exhibited superior photocatalytic performance, achieving higher yields of benzaldehyde (6.79 μmol g-1 h-1) and H2 (7.16 μmol g-1 h-1) compared to α-NiS/RP, α-β-NiS(glo)/RP and α-β-NiS(fla)/RP. The observed enhancement in photocatalytic activity can primarily be attributed to the distinct carrier separation mechanisms, specifically the Ohmic contact in the β-NiS/RP system and the Schottky junction in the α-NiS/RP system. This study introduces an effective strategy for optimizing carrier migration mechanisms in composite catalysts via crystal phase modulation, thereby providing valuable insights into the design of highly efficient photocatalysts for energy and environmental applications.