Boosting photocatalytic H2O2 evolution via S-scheme charge routing in N,S-doped carbon dots/g-C3N4 heterojunctions

The solar-driven synthesis of hydrogen peroxide (H 2 O 2 ) using graphitic carbon nitride (g-C 3 N 4 ) is inherently limited by rapid charge recombination and insufficient light absorption. To address this issue, pre-synthesized nitrogen and sulfur co-doped carbon dots (N,S-CDs) were introduced onto g-C 3 N 4 nanosheets via a hydrothermal pre-anchoring strategy followed by calcination. The as-synthesized N,S-CDs/g-C 3 N 4 composites exhibited an enhanced H 2 O 2 production rate (1162.8 μmol·g −1 ·h −1 ), which was approximately 4.7 times higher than that of pristine g-C 3 N 4 . The improvement of photocatalytic activity was primarily attributable to the construction of step-scheme (S-scheme) heterojunction, which not only expedited the spatial separation of photogenerated charge carriers but also preserved the high redox potentials essential for efficient H 2 O 2 synthesis. Furthermore, the N,S-CDs broadened the light absorption range, enabling more effective utilization of visible light. This work provides a promising strategy for rational design of CD-based heterojunctions toward high-efficiency solar-driven H 2 O 2 production.