Investigating the electrochemical advanced oxidation mechanism of N-doped graphene aerogel: Molecular dynamics simulation combined with DFT method

Nitrogen-doped graphene as a perfectly-efficient and environmentally compatible electrocatalyst won widespread attention in electrochemical advanced oxidation processes (EAOP). However, the relationship between surface structure regulation and activity of catalysts is still lacking in systematic scientific guidance. Herein, nitrogen-doped graphene aerogel (NGA) was conveniently prepared through hydrothermal treatment, and then utilized to fabricate the gas diffusion electrode (GDE) as the cathode for tetracycline (TC) removal. High free radical yield (81.2 μM) and fast reaction rate (0.1469 min-1) were found in NGA system. The molecular dynamics simulation (MD) results showed that the interaction energy of NGA was greater than the raw graphene aerogel (GA). The adsorption activation of H2O2 and the degradation of TC occurred in the first adsorption layer of catalysts, and both processes turned more orderly after nitrogen doping. Moreover, the van der Waals interaction was stronger than the electrostatic interaction. Density function theory (DFT) revealed that the adsorption energy of H2O2 at graphitic N, pyridinic N, and pyrrolic N sites was -0.03 eV, -0.39 eV, and -0.30 eV, respectively. Pyridinic N sites were inferred as the main functional regions of in-situ activation •OH, there were more likely to occur ectopic reaction in pyrrolic N, and graphitic N were responsible for improving H2O2 production. By revealing the microstructure and activation characteristics of NGA, an experiment-simulation complementary strategy is provided in the EAOP to discover or to optimize new catalysts.