Boosting TiO ₂ Photocatalytic H ₂ O ₂ Production via S, N‐Codoped Lignin‐Derived Carbon Dots: Quantifying the Enhancement Role

ABSTRACT Carbon dots (CDs) have emerged as promising modifiers for boosting the photocatalytic H 2 O 2 production, yet their precise role remains to be quantitatively elucidated. Herein, S, N‐codoped lignin‐derived carbon dots (SN‐LCDs) and lignin‐derived carbon dots (LCDs) were synthesized and employed to modify TiO 2 . Under simulated solar light irradiation, the SN‐LCDs/TiO 2 exhibited the highest H 2 O 2 production performance of 1601.6 μmol g −1 h −1 , which was 11.7 and 2.2 times that of pristine TiO 2 (136.8 μmol g −1 h −1 ) and LCDs/TiO 2 (715.6 μmol g −1 h −1 ), respectively. Through systematic investigations of the 2e − oxygen reduction reaction (ORR) kinetics, interfacial charge transfer kinetics, and photoelectrochemical characterization, a novel quantitative evaluation system based on enhancement factor (EF) was established. SN‐LCDs primarily enhanced the TiO 2 performance by inhibiting H 2 O 2 decomposition (EF = 3.27) and enhancing ORR activity (EF = 2.63). Additional contributions include the expansion of the solar light absorption range (EF = 2.32), promotion of e − –h + separation and migration (EF = 1.82), and improvement of selectivity toward the 2e − ORR pathway (EF = 1.66). The in situ characterization and density functional theory calculations further revealed the key role and mechanism of SN‐LCDs in enhancing TiO 2 photocatalytic H 2 O 2 production. This study not only advances the mechanistic understanding of CD‐enhanced photocatalysts but also provides a strategic framework for optimizing CD‐modified photocatalytic systems.