Z-scheme photocatalyst sheets with P-doped twinned Zn0.5Cd0.5S1-x and Bi4NbO8Cl connected by carbon electron mediator for overall water splitting under ambient condition

Abstract

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 Zn0.5Cd0.5S1-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.