Photocatalytic Redox Coupling Toward Simultaneous Energy Conversion and Chemical Synthesis: A Critical Review of Sacrificial-Agent-Free Systems

Abstract The photocatalytic coupling strategy integrates two or more thermodynamically and kinetically compatible redox half-reactions, enabling the simultaneous utilization of photogenerated electrons and holes without recourse to external sacrificial agents. This approach not only effectively overcomes the inherent performance bottlenecks of conventional photocatalytic systems but also achieves the dual goals of energy conversion and high-value-added product synthesis. This review systematically summarizes the research progress of three major categories of reaction systems which includes H2 production coupling, CO2 reduction coupling, and H2O2 generation coupling, with a primary focus on practical applications in high-value-added reactions such as organic transformation, biomass upgrading, and pollutant degradation. From the perspective of material design, this review thoroughly elucidates the fundamental underlying mechanisms of key strategies, including internal electric field regulation, heterojunction construction, and defect engineering, while critically discussing the synergistic effects of diverse coupled systems on enhancing energy efficiency and producing high-value-added chemicals. Furthermore, this review recapitulates the latest cutting-edge advancements in photocatalytic coupling systems, outlines the challenges and prospects for future development, and holds profound implications for propelling the advancement of solar-driven chemical processes and energy conversion technologies.