Insights into transition metal encapsulated N-doped CNTs cathode for self-sufficient electrocatalytic degradation

In electrochemical advanced oxidation processes (EAOPs), a series of transition metal encapsulated nitrogen-doped carbon nanotubes ([email protected], M=Fe, Co, Ni, Cu) as bifunctional cathodes were synthesized to compare and uncover their activity trends, fulfilling the self-sufficient electrocatalytic degradation. The sulfamethazine (SMT) degradation activity trends were follows: [email protected]>[email protected]>[email protected]>[email protected] cathode at pH≤ 7, while the [email protected] cathode exhibited the highest activity at pH 9 due to the more 1O2 and atomic H*. In-situ Fourier transformed infrared (FTIR) spectroscopy and density functional theory (DFT) calculation suggested that the atomic H* was easier to generate under the action of pyridinic N on [email protected] cathode. Overall, various pollutants degradation on [email protected] cathode performed with good stability with low leaching iron (0.12 mg L−1) and low energy consumption (<0.3 kWh∙log−1∙m−3). This study sheds light on different mechanisms of reactive species production on [email protected] cathode, thus providing guidance for the selectivity between [email protected] via active species and pollutants.