Fe0.5Co0.5-Co1.15Fe1.15O4/carbon composite nanofibers prepared by solution blow spinning: Structure, morphology, Mössbauer spectroscopy, and application as catalysts for electrochemical water oxidation

Abstract

In this work, we report the synthesis of Fe0.5Co0.5-Co1.15Fe1.15O4/carbon composite nanofibers by solution blow spinning (SBS) and study their structure, morphology, and catalytic activity toward the oxygen evolution reaction (OER, electrochemical water oxidation) in an alkaline medium. The solution blow spun fibers, prepared using nitrate precursors (Fe and Co) and poly(vinyl pyrrolidone, PVP), were calcined at 620 °C for 1 h in argon atmosphere. The thermogravimetric test shows that the stabilization of mass loss and the formation of the compound occur at ∼600 °C. X-ray diffraction revealed the presence of two crystalline phases, Fe0.5Co0.5 and Co1.15Fe1.15O4, with crystallite sizes of 16.5 nm and 18.1 nm, respectively. Scanning and transmission electron microscopies show that the average fiber and nanoparticle diameters are 362 nm and 28.41 nm, respectively. The quantification of Fe0.5Co0.5 and Co1.15Fe1.15O4 phases determined by the Rietveld refinement agrees well with the relative absorption area (RAA) values obtained by Mössbauer spectroscopy. Electrochemical analyses of Fe0.5Co0.5-Co1.15Fe1.15O4/carbon composite nanofibers supported by commercial Ni foam reveal a low overpotential value of η = 308 mV at 10 mA cm−2 and only 400 mV to generate 450 mA cm−2. The chronopotentiometry test over 15 h indicates that Fe0.5Co0.5-Co1.15Fe1.15O4/carbon nanofibers have excellent chemical and mechanical stability for their use as electrodes for water oxidation.