Electrocatalytic degradation of nitrogenous heterocycles on confined particle electrodes derived from ZIF-67

Nitrogen-containing heterocyclic compounds (NHCs) are hazardous, toxic, and persistent pollutants, thereby requiring urgent solutions. Herein, ZIF-67 was compounded with powder-activated carbon (PAC) to prepare Co/NC/PAC (NC i.e. nitrogen-doped carbon) particle electrodes for the electrocatalytic treatment of pyridine and diazines . Co/NC/PAC reflected the confinement of Co 3 O 4 /CoN/Co 0 into the N-doped graphitic-carbon layer to generate both pyrrolic-N and graphitic-N active sites. Under the optimal conditions (0.3 A, 12 mL min −1 , and initial pH 7.00), the degradation of four NHCs realized 90.2–93.7% efficiencies. The number and position of N atoms in NHCs directly affected the degradation efficiency. The following increasing order of facilitated degradation was recorded: pyridazine <  pyrimidine <  pyrazine < pyridine. The as-obtained Co/NC/PAC possessed the direct redox effect on NHCs, achieving fast electrocatalytic rate. Species like ·OH and H* were detected in Co/NC/PAC system with contributions to NHCs degradation estimated to 24% and 34%, respectively. Density functional theory (DFT) calculations revealed H* susceptible to attacking the N position, while the meta-position of C was subject to  hydroxyl radical (·OH) addition. Overall, degradation of NHCs was achieved by hydro-reduction, oxidation , ring opening cleavage, hydroxylation, and mineralization. Ring-cleavage and mineralization of NHCs provided a novel electrochemical strategy to refractory wastewater treatment .