Advanced graphene-silica fume/polyaniline-iron nanoparticle composite electrocatalyst for efficient oxygen reduction in alkaline media.

The development of low-cost, efficient and stable electrocatalysts for oxygen reduction reaction is critical for advancing energy conversion and storage technologies. The oxygen reduction reaction (ORR) is a key electrochemical process in energy conversion systems, particularly in fuel cells, where it governs the overall efficiency of the device. This study explores the electrochemical performance of a novel carbon paste electrode (CPE) modified with silica fume (SF), polyaniline (PANi), and iron nanoparticles (FeNPs) for potential application in fuel cells and supercapacitors. A stepwise electrode modification approach was employed to fabricate CPE/SF, CPE/SF/PANi, and CPE/SF/PANi/FeNP nano-composite electrodes. The structural and morphological characteristics of the modified electrodes were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Electrochemical properties were assessed via cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). The incorporation of PANi and FeNPs significantly enhanced the electrocatalytic activity of the electrode, as evidenced by increased current densities and reduced onset potentials in methanol oxidation and oxygen evolution reactions (OER). EIS data demonstrated a marked decrease in charge transfer resistance, indicating improved electrical conductivity. The results confirmed that the reactions were diffusion-controlled. Chronoamperometric analysis further revealed superior long-term stability and resistance to electrode poisoning in the FeNP-modified electrodes. The addition of SF resulted in a substantial 7.235-fold increase in current density, with the initial values determined as 1.089 mA cm⁻² for CPE/PANi and 7.879 mA cm⁻² for CPE/PANi/SF.These results highlight the synergistic effects of combining SF, PANi, and FeNPs, offering promising prospects for use in energy-related applications.