Abstract: Photocatalysis is a green and environmentally-friendly process that utilizes the ubiquitous intermittent sunlight. To date, an emerging S-scheme heterojunction across the intimately coupled heterojunction materials is proposed to surpass the efficiency of conventional II-type and Z-type photocatalysis. Furthermore, S-scheme heterojunction photocatalysts with greatly improved photocatalytic performance have gained significant attention due to their fast charge carriers separation along with strong redox ability and stability, since its proposal in 2019. Herein, a timely and comprehensive review is highly desired to cover the state-of-the-art advances. Driven by this idea, the review conveys the recent progress and provides new insights into further developments. Unlike the conventional method, in this review, we implement a quantification model to outline current trends in S-scheme heterojunctions research as well as their correlations. The overview begins with the fundamentals of four basic photocatalytic mechanisms, followed by its design principles. Afterward, diverse characterization techniques used in the S-scheme heterojunctions are systematically summarized along with the modification strategies to boost photocatalytic performances. Additionally, the internal reaction mechanism and emerging applications have been reviewed, including water conversion, CO₂ remediation, wastewater treatment, H₂O₂ production, N₂ fixation, etc. To sum up the review, we present several current challenges and future prospects of the S-scheme heterojunctions photocatalysts, aiming to provide indispensable platforms for the future smart design of photocatalysts.

Key words: S-scheme heterojunctions, Photocatalysts, Modification strategies, Charge separation mechanism