Enhanced oxygen reduction of multi-Fe3O4@carbon core–shell electrocatalysts through a nanoparticle/polymer co-assembly strategy

Abstract

This paper reports a facile synthesis of multi-Fe₃O₄@carbon (mFe₃O₄@C) core–shell nanoparticles (NPs) using co-assembly of Fe₃O₄ NPs and polystyrene-b-poly(ethylene oxide) (PS-b-PEO) as a template. Slow solvent exchange leads to multiple tiny hydrophobic Fe₃O₄ NPs entrapped within PS-b-PEO micelles. After polydopamine coating and subsequent carbonization, a carbon shell encapsulating multiple Fe₃O₄ cores is obtained. The significant features of mFe₃O₄@C lie in the more active Fe₃O₄ sites and available free space within the carbon shell. As a result, the oxygen reduction performance of the resultant mFe₃O₄@C shows a higher onset potential than that of single Fe₃O₄@C. Meanwhile, mFe₃O₄@C exhibits a larger limiting current density (5.2 mA cm⁻² at 1.0 V), long-time stability, and methanol tolerance compared to commercial Pt/C. The generality of the micellar immobilized NPs as a template is expected to boost the fabrication of various core–shell NPs for practical applications.