A hydrothermal pretreatment-assisted heterogeneous molten salt strategy to synthesize crystalline carbon nitride for solar-driven H2O2 production.

Interfacial effects critically regulate photocatalytic pathways through charge transfer modulation, reactant enrichment, and transition-state stabilization. However, precisely manipulating free electrons to drive efficient O2 reduction to H2O2 remains challenging. To address this, we develop a hydrothermal pretreatment-assisted heterogeneous molten salt strategy to synthesize crystalline carbon nitride (S/Cl-CN). This approach synergistically integrates molten KSCN (enabling rapid mass transfer and in situ generation of electron-withdrawing CN groups) with solid KCl (providing spatial confinement for oriented crystallization). The heterogeneous environment optimally tunes interfacial effects, enhancing structural order and charge separation efficiency. The resulting S/Cl-CN exhibits extended visible-light absorption (narrowed bandgap 2.67 eV), accelerated carrier mobility and optimized O2 adsorption sites via CN-induced electron redistribution. These properties enable record H2O2 production rates of 4.58 mM g-1 h-1 in pure water (17-fold higher than the reference) and 177.1 mM g-1 h-1 with the sacrificial agent. Mechanistic studies confirm interfacial engineering promotes two-step single-electron oxygen reduction (via stabilized OOH⁎ and HOOH⁎ intermediates), complementary water oxidation pathways and reduced energy barriers for O2 activation and conversion. This work resolves electron-manipulation challenges in photocatalytic H2O2 synthesis and establishes a scalable molten salt platform for interface-optimized catalyst design.