• • Nv-C3N4-CNT/GF electrode achieved a charge transfer resistance of 13.26 Ω and a double-layer capacitance (Cdl) of 3.75 mF·cm−2, 3.30 times higher than pristine GF, indicating enhanced electrocatalytic activity and active site density.
• • Under RSM-optimized conditions (current density 41.24 mA·cm−2, pH 7.23, catalyst content 1.02 g, calcination temperature 305.42 °C), H2O2 production reached 1638.73 mg·L−1, with a relative error of 0.92% from the predicted value, confirming model accuracy.
• • The electrode demonstrated robust durability: after 6 cycles, H2O2 production decreased by only 13.688%, and in a 1.25 L, 0.1 mol·L−1 Na2SO4 solution, maximum production reached 2014.04 mg·L−1 over 960 min, with a peak Faradaic efficiency of 54.86%.
• • The Nv-C3N4-CNT/GF electrode outperformed g-C3N4-CNT/GF and CNT/GF by 1.3 and 1.5 times in H2O2 yield (1622.73 mg·L−1 at 90 min), demonstrating the critical role of nitrogen vacancies in enhancing 2e−ORR selectivity and activity.