The effect of N-doping on the synergy between adsorption and 2e-ORR performance of activated carbon cathode in an electro-Fenton system

•Pyrrolic-N and pyridinic-N can promote the adsorption capacity of activated carbon cathode.•Graphitic-N and pyridinic-N are beneficial to the 2e-ORR on activated carbon cathode.•The appropriate proportion of N-doping type is beneficial to the synergy between adsorption and 2e-ORR.•Excellent synergy can further improve the removal efficiency of TC by electro-Fenton system. The adsorption of carbon materials and 2e-ORR performance can be promoted by N-doping. However, the effect of different N-doping types on adsorption and 2e-ORR and their synergy is not clear, which limits the development of an electro-Fenton system. To enhance the degradation efficiency of the electro-Fenton system, it is essential to understand the mechanisms involved in regulating cathode performance. To achieve this goal, a multi-scale simulation approach was employed that integrates molecular dynamics and quantum chemical simulations. This method was utilized to fabricate carbon planes with various N-doping types. The simulation results showed pyridinic-N and pyrrolic-N showed a cooperative effect and promoted the capacity of activated carbon to adsorb tetracycline. Graphitic-N and pyridinic-N greatly improved the selectivity of 2e-ORR, which is conducive to the formation of H2O2. Experimental investigations have revealed a synergistic association between adsorption and 2e-ORR, and suboptimal performance of either process can hinder the degradation efficacy of electro-Fenton. The reason for this is that an exceptional selectivity of 2e-ORR enhances the production of ·OH, and good adsorption capability facilitates the utilization of ·OH. The MAC cathode exhibits a greater synergistic effect between adsorption and 2e-ORR owing to the suitable proportion of pyridinic-N, pyrrolic-N, and graphitic-N. Under the action of high-efficiency synergy, the degradation effect of tetracycline by the electro-Fenton cathode was 8.72%-11.64% higher than that of other modified cathodes. The outcomes of our investigation provided insights into the approach for targeted control of the performance of N-doped modified cathodes in the electro-Fenton system.