Photocatalytic Z‐scheme Overall Water Splitting: Insight into Different Optimization Strategies for Powder Suspension and Particulate Sheet Systems

Abstract Achieving solar light‐driven photocatalytic overall water splitting is the ideal and ultimate goal for solving energy and environment issues. Photocatalytic Z‐scheme overall water splitting has undergone considerable development in recent years; specific approaches include a powder suspension Z‐scheme system with a redox shuttle and a particulate sheet Z‐scheme system. Of these, a particulate sheet has achieved a benchmark solar‐to‐hydrogen efficiency exceeding 1.1 %. Nevertheless, owing to intrinsic differences in the components, structure, operating environment, and charge transfer mechanism, there are several differences between the optimization strategies for a powder suspension and particulate sheet Z‐scheme. Unlike a powder suspension Z‐scheme with a redox shuttle, the particulate sheet Z‐scheme system is more like a miniaturized and parallel p/n photoelectrochemical cell. In this review, we summarize the optimization strategies for a powder suspension Z‐scheme with a redox shuttle and particulate sheet Z‐scheme. In particular, attention has been focused on choosing appropriate redox shuttle and electron mediator, facilitating the redox shuttle cycle, avoiding redox mediator‐induced side reactions, and constructing a particulate sheet. Challenges and prospects in the development of efficient Z‐scheme overall water splitting are also briefly discussed.