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Doping with nitrogen atoms can improve the catalytic activity of activated carbon cathodes in electro-Fenton systems, but currently there is a lack of understanding of the catalytic mechanism, which limits the further development of high-performance activated carbon cathodes. Here, a multi-scale exploration was conducted using density functional theory and experimental methods to investigate the mechanism of different nitrogen doping types promoting the redox performance of activated carbon cathodes and the degradation of phenol. The density functional theory results indicate that the introduction of nitrogen atoms enhances the binding ability between carbon substrates and oxygen-containing substances, promotes the localization of surrounding electrons, and makes it easier for O 2 to bind with protons and catalyze the hydrogenation reaction of *OOH. Due to its weak binding ability with oxygen-containing substances, AC is difficult to form H 2 O 2 , resulting in a tendency towards the 4e−ORR pathway. The binding energy between graphite-N carbon substrate and pyridine-N carbon substrate with *OOH is closer to the volcano top, so graphite n and pyridine n can better promote the selectivity of activated carbon for 2e-ORR. In addition, the calculation results also indicate that pyrrole-N and graphite-N are more capable of catalyzing the reaction energy barrier between ·OH and phenol. Finally, the simulation results were used to guide the modification of nitrogen doped activated carbon and experimental verification was carried out. The degradation results of phenol confirmed the efficient synergistic effect between different types of nitrogen doping, and the NAC-800 electrode exhibited efficient and stable characteristics. This work provides a guiding strategy for further developing stable and highly selective activated carbon cathode materials. • Nitrogen doping improves the bonding ability between AC cathode and *OOH. • Graphene-N and pyridine-N increased the 2e-ORR selectivity of activated carbon. • Pyrrorole-N and graphite-N have catalytic effects on the degradation of phenol. • There are effective synergies between different types of nitrogen doping. • Nitrogen doping can promote the formation of H 2 O 2 and the degradation of phenol. [ABSTRACT FROM AUTHOR]

The use of the electro-Fenton process to continuously generate H 2 O 2 and efficiently degrade organic pollutants is considered a promising technology. The ratio of generation of H 2 O 2 is usually regarded as the critical step; however, how the H 2 O 2 is utilized is also of particular importance. Herein, activated carbon was activated at different temperatures and used to explore the effect of nitrogen doping on the production and utilization of H 2 O 2 in the electro-Fenton-based degradation of organic pollutants. The experimental results indicate that nitrogen-doped activated carbon simultaneously promotes the generation and utilization of H 2 O 2 , which is attributed to the regulation of the competition between phenol and O 2 adsorption by the doped nitrogen. Nitrogen doping not only improves 2e−ORR selectivity but also aggregates phenol near the cathode to balance the concentrations of phenol and ·OH. Density functional theory (DFT) calculations further confirmed that pyrrole-N as a dopant promoted the adsorption of phenol, while pyridine-N was more favorable for O 2 adsorption. The unique balance of nitrogen types possessed by modified activated carbon NAC-750 permits the efficient synergistic generation and utilization of H 2 O 2 in a balanced manner during the degradation of phenol. This work provides a new direction for the rational nitrogen-doping modification of activated carbon for the electro-Fenton-based degradation of organic pollutants. [Display omitted] • The adsorption of phenol affects the adsorption of O 2 and the generation of H 2 O 2. • Graphite-N is the main site for the competitive adsorption of phenol and O 2. • Competition can be effectively regulated by regulating nitrogen doping types. • Reasonable nitrogen doping can promote the generation and utilization of H 2 O 2. [ABSTRACT FROM AUTHOR]