Mechanistic Analysis of the Synergic Enhancement Effect of Doping and Defects on Hydrogen Peroxide Production in Crystalline Carbon Nitride

Graphitic carbon nitride (g-C₃N₄) assisted photocatalytic hydrogen peroxide (H₂O₂) production has garnered significant interest due to its environmental sustainability. This study successfully synthesizes the crystalline material NaLi-CN via a simple molten salt-assisted method, simultaneously introducing Na⁺ dopant alongside nitrogen vacancies and cyanide groups. The obtained photocatalyst exhibits exceptional H₂O₂ production capacity, reaching 25.65 mmol g^-1 h^-1, representing a 113-fold enhancement over pristine g-C₃N₄. This performance enhancement stems from its highly crystalline structure, which effectively reduces the interlayer spacing and significantly promotes in-plane and interlayer electron migration. Moreover, a synergistic effect between Na⁺ dopant and defect structures not only broadens the light absorption range but also significantly enhances charge separation efficiency. Interestingly, NaLi-CN enables simultaneous activation of multiple reaction pathways in the presence of a sacrificial agent, collectively suppressing competing reactions and dramatically enhancing two-electron oxygen reduction reaction selectivity. This study elucidates the synergic role of doping and defects in crystalline carbon nitride and provides valuable insights for designing efficient photocatalytic systems by optimizing the H₂O₂ production reaction pathways.