Intercalation of Nanosized Fe3C in Iron/Carbon To Construct Multifunctional Interface with Reduction, Catalysis, Corrosion Resistance, and Immobilization Capabilities

As a robust reducing system in industrial wastewater treatment, iron/carbon (Fe/C) microelectrolysis suffers from surface passivation and low utilization efficiency. Herein, we introduced Fe3C into the Fe/C system to develop a core-shell Fe0/Fe3C/C nanorod with a multifunctional interface (Fe3C/C) providing reduction, catalysis, adsorption, and corrosion resistance. The results proved that the fabricated Fe0/Fe3C/C possesses 5.6 times higher reduction capacity (220 mg/g) for Cr(VI) reduction but a relatively lower Fe leakage (2.7 mg/L) than Fe/C. On the basis of the results of electrochemical characterization (Tafel polarization curves and electrochemical impedance spectroscopy), the corrosion-resistant Fe3C/C shell can significantly prevent surface passivation of the Fe0 core, whereas Fe3C efficiently catalyzes electron transfer from the inner Fe0 to the external carbon surface. Moreover, the reductive species involved in Cr(VI) removal were identified as hydrogen atoms, adsorbed Fe(II) ions, and electrons tunneling from Fe0. STEM, XPS, and Mössbauer spectroscopies were further adopted to characterize the interface reaction of Fe0/Fe3C/C during the Cr(VI) removal process. Finally, the reaction mechanism for Cr(VI) reduction over Fe0/Fe3C/C was proposed, and the distribution of active sites was inferred.