Proton-rich interfaces and long-lived carriers synergistically boost the kinetics of photocatalytic hydrogen peroxide production over sulfonated carbon nitride.

The insufficient photogenerated carrier lifetime and sluggish charge transport are two key factors limiting the efficiency of graphitic carbon nitride catalysts for the photosynthesis of hydrogen peroxide (H2O2). Herein, we propose a strategy that prolongs the photogenerated carrier lifetime and accelerates charge and proton transport via two microenvironment modulation strategies, thereby enhancing H2O2 synthesis performance. Photocatalytic H2O2 generation experiments demonstrate that the optimal (DSCN) achieves a significantly enhanced H2O2 production rate of 14.35 mmol g-1 h-1 in a system containing sacrificial agent, with an apparent quantum yield (AQY) of 11.9% at 400 nm and a solar-to-chemical energy conversion efficiency of 0.37%. Femtosecond transient absorption spectroscopy (fs-TA) and time-resolved photoluminescence spectroscopy (TRPL) indicate that sulfonic acid functionalization can effectively modulate the interfacial electron and charge dynamics, promote charge separation and significantly extend the lifetime of photogenerated carriers. More importantly, density functional theory (DFT) calculations combined with experimental results reveal a primary two-step single-electron oxygen reduction reaction mechanism involving sulfonic acid-functionalized interfaces that modulate the local electronic structure and construct a proton-rich microenvironment, significantly promoting O2 activation and *OOH intermediate formation. In addition, DSCN exhibits excellent H2O2 synthesis capability in various real water samples and continuous-flow reactors, and demonstrates great potential for practical application in the degradation of environmental pollutants.