N-doped carbon-coated Fe3N composite as heterogeneous electro-Fenton catalyst for efficient degradation of organics

Herein, the application of a N-doped graphitic-carbon-coated iron nitride composite dispersed in a N-doped carbon framework (Fe3N@NG/NC) is investigated as a heterogeneous electro-Fenton (HE-EF) catalyst for the efficient removal of organics. The simultaneous carbonization and ammonia etching of iron-based metal organic framework (Fe-MOF) materials yielded well-dispersed N-doped carbon-coated Fe3N nanoparticles with a diameter of ~70 nm. The Fe3N and pyridinic N endowed the composite with high HE-EF activity for decomposing the electrogenerated H2O2 to •OH. The Fe3N@NG/NC exhibited outstanding HE-EF performance in removing various organic pollutants with low iron leaching. A removal rate of 97–100% could be obtained for rhodamine B (RhB), dimethyl phthalate, methylene blue, and orange II in 120 min at a pH of 5.0. When the solution pH was set to 3.0, 5.0, 7.0, and 9.0, the removal rate of RhB reached 100%, 96%, 92%, and 81%, respectively, in 60 min at an optimum voltage of 0.0 V (vs. reversible hydrogen electrode (RHE)). Moreover, the concentration of leached iron was expected to be below 0.03 mg/L in a wide pH range of 3.0–9.0. In addition, the RhB removal efficiency remained as high as 90% after six cycles in the reusability experiments. This work highlights the MOF-derived Fe3N composite as an efficient HE-EF catalyst and the corresponding catalytic mechanism, which facilitates its application in wastewater treatment.