Charge Transfer Modulation in g-C₃N₄/CeO₂ Composites: Electrocatalytic Oxygen Reduction for H₂O₂ Production

The electrocatalytic two-electron oxygen reduction reaction (2e-ORR) represents one of the most prospective avenues for the <i>in situ</i> synthesis of hydrogen peroxide (H₂O₂). However, the four-electron competition reaction constrains the efficiency of H₂O₂ synthesis. Therefore, there is an urgent need to develop superior catalysts to facilitate the H₂O₂ synthesis. In this study, graphite-phase carbon nitride and cerium dioxide composites (g-C₃N₄/CeO₂) with varying CeO₂ loadings were prepared with favorable 2e-ORR electrocatalysts. The optimized composite, containing 20 wt % CeO₂ (g-C₃N₄/CeO₂-20%) exhibited the highest Faradaic efficiency (FE) of 97% and notable H₂O₂ yielding of 9.84 mol g_cat.^-1 h^-1 at the potential of 0.3 V (vs RHE) in a 0.1 M KOH electrolyte. Density functional theory calculations revealed that the improvement of the selectivity and yield of H₂O₂ for the composites were attributed to the charge transfer between g-C₃N₄ and CeO₂, which causes the active site C atom donating electrons to form C⁺, thereby enhancing the adsorption and desorption of *OOH intermediates. Additionally, the g-C₃N₄/CeO₂-20% composite exhibits excellent 2e-ORR performance in neutral and acidic electrolytes and demonstrates superior capability in electro-Fenton degradation of organic pollutants. This study not only provides new insights into the electrocatalytic mechanism of g-C₃N₄/CeO₂ composites but also demonstrates an effective method for designing 2e-ORR catalysts.