Abstract: Against the backdrop of the global "dual-carbon" strategy, solar-driven photocatalysis emerges as a promising avenue for clean energy conversion and carbon neutralization. However, conventional single photocatalysts suffer from rapid carrier recombination and mismatched redox reaction kinetics, severely limiting their catalytic performance. Different from conventional heterojunctions that compromise redox potential for enhanced charge separation, S-scheme heterojunctions feature a unique band alignment that selectively eliminates useless low-energy carriers via interfacial recombination. This configuration preserves high-energy electrons and holes with robust redox capabilities, fundamentally resolving the intrinsic trade-off between charge separation efficiency and thermodynamic redox driving force in photocatalysis. Based on this working principle, this review systematically elucidates the efficient utilization mechanism of electron-hole pairs in S-scheme heterojunctions, with a specific focus on the synergistic promotion mechanism between paired reduction and oxidation half-reactions in photocatalytic redox coupling systems. We highlight three major categories of reduction reactions—hydrogen production, CO₂ reduction, and H₂O₂—coupled with diversified value-added oxidation processes (e.g., organic molecule oxidation, biomass upgrading, and pollutant oxidative degradation). Through the rational regulation of active site construction, band structure engineering, and interfacial charge modulation in S-scheme heterojunctions, the reaction kinetics, conversion efficiency, and catalytic pathways of both reduction and oxidation half-reactions can be synchronously optimized, which substantially improves the atom utilization efficiency and overall economic value of solar energy photocatalytic conversion. This review systematically clarifies the intrinsic correlation and synergistic mechanism between S-scheme heterojunction design and dual-reaction coupling catalysis, aiming to provide feasible theoretical guidance and technical roadmaps for the rational construction of high-efficiency, low-cost, and multifunctional solar-driven photocatalytic systems.

Key words: S-scheme heterojunction, Dual reactions, Charge separation, Electron-hole synergy, Redox photocatalysis