All-Solid-State C₃N₄/Ni_xP/Red Phosphorus Z-Scheme Heterostructure for Wide-Spectrum Photocatalytic Pure Water Splitting

Z-scheme photocatalysts encouraged by natural photosynthesis have received increasing attention for pure water splitting. However, there have been only a few instances of effective Z-scheme nanosystems utilizing nonmetal photocatalysts for both water reduction and oxidation. In this study, we used carbon nitride (CN), metallic Ni_xP, and crystalline red phosphorus (RP) to build a solid-state Z-scheme photocatalytic system, which worked as reduction sites, an electron mediator, and oxidation sites, respectively. The light absorption capability up to ∼600 nm enabled the photocatalyst to realize water splitting under broad-spectrum illumination. Detailed analysis suggested that the photocatalytic hydrogen production rate was apparently enhanced on account of effective spatial separation of light-induced charges owing to the intimate contact between the Ni_xP mediator and photocatalyst components as well as the suitable energy band alignment. Meanwhile, hydrogen peroxide instead of oxygen was generated from water oxidation, which can solve the separation and safety issues of the synchronized production of hydrogen and oxygen and thus facilitated the feasible application of photocatalytic hydrogen production.