Corncob biochar–supported Pd electrocatalysts for ethanol oxidation reaction in alkaline medium: Effect of pyrolysis temperature and addition of Ni

Abstract

This study investigated Pd-based electrocatalysts supported on corncob-derived biochar, pyrolyzed at various temperatures, for ethanol oxidation reaction in an alkaline medium, addressing challenges in direct ethanol fuel cells (DEFCs). Biochar, pyrolyzed at various temperatures (i.e., from 600 to 1000°C) displayed porous morphology and surface oxygenated groups, as confirmed by scanning electron microscopy and energy dispersive x-ray (SEM–EDX) and Fourier transform Infrared (FTIR) spectroscopy. The corncob biochar revealed a mesoporous structure based on Brunauer-Emmett-Teller (BET) analysis with graphitic carbon as confirmed by X-ray diffraction (XRD) analysis. The prepared Pd/biochar, with a trace amount of Ni, was investigated by SEM–EDX, transmission electron microscopy (TEM), XRD, and X-ray photoelectron spectroscopy (XPS). Among the synthesized catalyst composites, PdNi/CB600 demonstrated the least positive onset potential (−0.719 V), highest anodic peak current density (21.69 mA·cm⁻²), and highest I_f/I_b ratio (0.851) toward ethanol oxidation reaction in an alkaline medium, as determined by cyclic voltammetry (CV) and Tafel plot studies. Chronoamperometric analysis demonstrated the superior stability of PdNi/CB600 (65.33%) compared to commercial PdNi/C. These results highlight the corncob biochar's superior electrocatalytic activity over commercial carbon black as a support material for Pd-based electrocatalysts in a basic medium.