Boosting photocatalytic H2O2 evolution through synergistic sulfur doping and crystalline engineering of carbon nitride

Abstract

The photocatalytic two-electron oxygen reduction reaction (2e⁻ ORR) presents a sustainable route for H₂O₂ production, yet its efficiency is constrained by limited light absorption, inefficient charge separation, and inadequate selectivity. Herein, a sulfur-doped crystalline carbon nitride (CSCN) is synthesized via a one-step potassium salt-mediated polymerization of sulfur-containing thiocyanuric acid. Combined theoretical and experimental analyses reveal that sulfur doping not only extends visible-light absorption by activating n → π* electronic transitions but also synergizes with intercalated K⁺ to induce a robust built-in polarization field, markedly facilitating photogenerated charge separation. Moreover, S-doping tailors the surface charge distribution, enhancing O₂ adsorption and steering the reaction pathway toward highly selective 2e⁻ ORR. As a result, the optimized CSCN achieves superior H₂O₂ production rates of 185 μmol g⁻¹ h⁻¹ in pure water and 11.84 mmol g⁻¹ h⁻¹ in the presence of benzyl alcohol as an electron donor under visible light, significantly outperforming its pristine carbon nitride (CN), sulfur-doped carbon nitride (SCN), and crystalline carbon nitride (CCN) counterparts. This work demonstrates a synergistic strategy integrating atomic doping and crystallization engineering to simultaneously regulate the electronic structure and surface reactivity, offering a rational paradigm for designing high-performance carbon nitride-based photocatalysts.