A novel bifunctional particle electrode with abundant Fe/Fe3C and Fe-N-C sites to enhance the performance of electro-Fenton in degrading organic pollutant

Electro-Fenton (EF) technology emerges as a promising approach to address the treatment of persistent organic pollutants. Nevertheless, its practical implementation often comes with certain drawbacks, like the low H2O2 activation efficiency, poor pH adaptability, and difficult recycling of the catalyst. To this end, we introduced highly active Fe-N-C sites onto the surface of nitrogen-doped graphene, improved the chemical environment of its central Fe atoms with Fe/Fe3C nanoparticles, effectively regulated the multi-electron oxygen reduction process of the catalyst in the electrochemical reaction, and realized the efficient production and activation of H2O2 in the electro-Fenton process. The synthesized Fe/Fe3C@FeNG-1000 achieved efficient removal of refractory organic pollutants in neutral conditions. The rate constant of degradation for tetracycline hydrochloride (TC) in the electro-Fenton reaction system at pH 7 was recorded as 0.1011 min-1. Additionally, a removal rate of 67.4% for total organic carbon (TOC) was achieved in just 120 min. The treatment of actual wastewater also showed excellent performance, with an average specific energy consumption of 6.16 kWh kg-1 COD-1. Fe/Fe3C@FeNG-1000 can still achieve more than 90% degradation efficiency after 5 consecutive cycles of the experiment, showing excellent stability, and the catalyst can be conveniently retrieved via magnetic methods following the reaction. The results show that the Fe/Fe3C@FeNG-1000-EF system has a wide range of pH applicability, long-term stability and good recyclability, has a good application value in practical wastewater treatment.