Visible-Light Driven Z-Scheme Water Splitting over NiS/CdS/PtOx/WO3 through Modulating Redox Mediator Environments

Visible-light-driven Z-scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. However, developing the Z-scheme using long wavelength responsive sulfides as H-2-evolving photocatalysts remains challenging. Herein, the construction of Z-scheme photocatalytic systems for overall solar water splitting is described using CdS and WO3 as H-2-evolving and O-2-evolving photocatalysts, respectively, in the presence of a shuttle redox mediator. The stoichiometric water splitting into H-2 and O-2 under the solar-simulated irradiation was determined through optimization of cocatalyst, shuttle redox mediator, and pH conditions. The activity attenuation during the long-term reaction was mainly attributed to the backward reaction which can be alleviated by filling the system with moderate argon. This work provides a new photocatalysts combination for the Z-scheme overall water splitting, further reflecting the importance of modulation of redox mediator environments.