Iron oxide/porous carbon as a heterogeneous Fenton catalyst for fast decomposition of hydrogen peroxide and efficient removal of methylene blue

Abstract

A high performance Fe₃O₄/Fe/Fe₃C@PCNF heterogeneous Fenton catalyst was synthesized for aqueous H₂O₂ decomposition and was utilized to remove methylene blue in water. Surprisingly, Fe₃O₄/Fe/Fe₃C@PCNF showed an extremely fast decomposition rate; this rate ranked as the highest value reported to date. Furthermore, it showed efficient removal of methylene blue in water which was tested at different H₂O₂ concentrations and solution temperatures. Based on detailed characterization, several unique features of this catalyst were presumed to be responsible for its remarkable catalytic activity for H₂O₂ decomposition as follows: (1) the presence of Fe⁰ and delocalized π-electrons of graphitic layers promotes the reduction of Fe³⁺ to Fe²⁺; (2) the catalyst particles were partially covered with a few defective graphitic layers, and H₂O₂ decomposition could occur through these defects; (3) the defective graphitic layers partially covered the catalyst particle to force the decomposition reaction to occur only in the vicinity of carbon and Fe₃O₄. Finally, this presumption was proved through experiments by changing the activation time of Fe₃O₄/Fe/Fe₃C@PCNF. After H₂O₂ decomposition was completed, Fe₃O₄/Fe/Fe₃C@PCNF could be efficiently separated by an external magnetic field because of its ferromagnetic behavior. Fe₃O₄/Fe/Fe₃C@PCNF showed high removal activity of aqueous methylene blue tested under various conditions.