Effect of Palladium Loading on Catalytic Properties of Pd/GCE for the Electro-oxidation of Methanol, Formic Acid, and Ethylene Glycol

This study investigates the influence of the catalyst (Palladium, Pd) mass that loaded onto a glassy carbon electrode (GCE) on the catalytic activity of methanol (MEO), formic acid (FAEO), and ethylene glycol (EGEO) electro-oxidation, the corresponding principal anodic reactions in the direct methanol (DMFCs), formic acid (DFAFCs), and ethylene glycol (DEGFCs) fuel cells, respectively. By increasing the Pd loading at 0.1 V, the Pd surface area increased from 0.55 cm2 (2 min Pd deposition) to 1.94 cm2 (25 min Pd deposition) which increased the peak currents (IP) of MEO (from 0.181 to 0.608 mA), FAEO (from 0.236 to 1.303 mA), and EGEO (from 0.699 to 2.082 mA). Additionally, the increase in Pd loading shifted the oxidation peak potentials (EP) to higher values (from –0.014 to 0.2 V for MEO, from –0.15 to 0.36 V for FAEO, and from 0.11 to 0.44 V for EGEO). It is thought that increasing IP is related to the increased Pd surface area while the slow diffusion of ions (compared with the fast charge transfer) and/or increasing the distance for the electron transport over the electrode due to catalyst stacking were behind the potential shifts.