Z-scheme photocatalyst sheets with P-doped twinned Zn_0.5Cd_0.5S_1-x and Bi₄NbO₈Cl connected by carbon electron mediator for overall water splitting under ambient condition

Cutting edge research within solar energy harvesting focuses on H₂ production from photocatalytic overall water splitting (OWS) using artificial two-step photoexcitation system known as Z-scheme. Inspired by natural photosynthesis, Z-scheme imparts a unique vectorial electron transfer from the ingenious arrangement of PS I-PS II coupling connected by an electron mediator. This allows Z-scheme to confer efficient charge isolation and split water into its constituent components, hydrogen (H₂) and oxygen (O₂), at two different positions with strong redox ability. More recently, particulate Z-scheme photocatalyst sheets have been worth noting as potentially scalable approach for solar water splitting. In this contribution, particulate Z-scheme photocatalyst sheets were developed using P-doped twinned Zn_0.5Cd_0.5S_1-x (d-ZCS-P) as hydrogen evolution photocatalysts (HEP) and Bi₄NbO₈Cl as oxygen evolution photocatalysts (OEP), which both embedded on N-doped carbon nanotubes (N-CNTs) as carbon conductive film. Further surface modification on photocatalyst sheets through concerted deposition of co-catalyst and protective shell warrants an efficient overall water splitting from pure water, with a solar-to-hydrogen conversion efficiency (STH) of 0.15% under ambient condition. The rational Z-scheme configuration of photocatalyst sheets alleviates the effect of H⁺ and OH⁻ concentration overpotentials which in turn bolstering the photocatalytic performance and paves a promising way of solar energy augmentation.