Ionic-Liquid-Derived Nitrogen-Doped Carbon Electrocatalyst for Peroxide Generation and Divalent Iron Regeneration: Its Application for Removal of Aqueous Organic Compounds

We investigated the activities of the ionic-liquid-derived (by pyrolysis) nitrogen-doped carbon as the electrocatalyst for the two-electron oxygen reduction reaction (ORR) and regeneration of divalent iron in the electro-Fenton process, focusing on the pyrolysis-temperature-dependent evolution of the doping structure. The results provided insight into the evolution of the catalytic activity as a function of the pyrolysis temperature. On the basis of the XPS N 1s analysis, the pyrolysis temperature was optimized at the 900 °C since the pyridinic/graphitic N structures which are known to be active sites for the ORR were maximized (4.29% pyridinic N and 7.30% graphitic N). The carbonyl surface group, which is known to be an active site for the Fe 3+ /Fe 2+ redox, was also maximized at the pyrolysis temperature of 900 °C (1.11%). This catalyst, adopting two simultaneously working electrodes for in situ H 2 O 2 generation/Fe 2+ regeneration, was successfully applied to the removal of the azo-dye (Orange II, TOC removal ≈95%) and the trace pharmaceutical compounds [carbamazepine, amoxicillin (≈100% degradation within 90 min) and cimetidine (≈90% degradation within 180 min)]; the pyrolysis-temperature-optimized performance was superior to those of many conventional carbon-based electrocatalysts.