Na and S Co-Doped Carbon Nitride for Enhancing Photocatalytic Hydrogen Peroxide Production

Doping is an effective way to improve the separation efficiency of photogenerated carriers, widen visible light adsorption, and tune the band structure of carbon nitride (g-C₃N₄, CN). Herein, Na, S co-doped CN (CNNS-x) photocatalysts were successfully prepared by a one-step thermal polymerization method using urea and sodium thiosulfate as the raw materials. The incorporation of Na and S not only improves the visible light response intensity and photogenerated carrier separation efficiency of CN but also enhances oxygen adsorption capacity and optimizes the energy band structure of the CN. The optimal CNNS-2.5 photocatalyst revealed a significantly enhanced photocatalytic performance and yielded 4.85 mM (24.25 mmol·g^-1·h^-1) H₂O₂ in 1 h under visible light irradiation. The above yield is 4.71 times that of CN. It also revealed good stability in four cycles. The active species capture test and ESR revealed that the photocatalytic mechanism for H₂O₂ production on CNNS-2.5 was a two-step, single-electron oxygen reduction reaction (ORR) pathway.