Facilely tuning the coating layers of Fe nanoparticles from iron carbide to iron nitride for different performance in Fenton-like reactions.

In this study, a series of Fe-based materials are facilely synthesized using MIL-88A and melamine as precursors. Changing the mass ratio of melamine and MIL-88A could tune the coating layers of generated zero-valent iron (Fe) particles from FeC to FeN facilely. Compared to Fe/FeN@NC sample, Fe/FeC@NC exhibits better catalytic activity and stability to degrade carbamazepine (CBZ) with peroxymonosulfate (PMS) as oxidant. Free radical quenching tests, open-circuit potential (OCP) test and electron paramagnetic resonance spectra (EPR) prove that hydroxyl radicals (OH) and superoxide radical (O) are dominant reactive oxygen species (ROSs) with Fe/FeC@NC sample. For Fe/FeN@NC sample, the main ROSs are changed into sulfate radicals (SO) and high valent iron-oxo (Fe (IV)=O) species. In addition, the better conductivity of FeC is beneficial for the electron transfer from Fe to the FeC, thus could keep the activity of the surface sites and obtain better stability. DFT calculation reveals the better adsorption and activation ability of FeC than FeN. Moreover, PMS can also be adsorbed on the Fe sites of FeN with shorter FeO bonds and longer SO bonds than on FeC, the Fe (IV)=O is thus present in the Fe/FeN@NC/PMS system. This study provides a novel strategy for the development of highly active Fe-based materials for Fenton-like reactions and thus could promote their real application.