Electrocatalytic Properties and DFT Studies of Pd-Based Catalysts Supported on Ceria/Onion-like Carbon for Isopropanol Oxidation in Alkaline Medium

This study investigated the electrocatalytic performance of Pd-based catalysts supported on onion-like carbon (OLC) for isopropanol (IPA) oxidation in alkaline media (a direct isopropanol fuel cells (DIFC)). The synthesized and evaluated catalysts included PdNi/OLC, Pd/CeO₂/OLC, and PdNi/CeO₂/OLC, all of which demonstrated performances comparable to that of commercial Pd/C. These samples are characterized by physicochemical analytical methods such as X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) coupled with energy-dispersive X-ray (EDX), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS). Electrochemical measurements were also carried out using cyclic voltammetry (CV), chronoamperometry (CA), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The CV tests and Tafel analysis results revealed that PdNi/CeO₂/OLC exhibited the highest current response with an onset potential of −0.69 V and better kinetic activity of 136.9 mV/dec respectively. Chronoamperometric tests confirmed that PdNi/CeO₂/OLC maintains superior stability and antipoisoning properties, achieving stable current densities over extended periods. EIS showed the lowest charge transfer resistance (R_ct) for PdNi/CeO₂/OLC, reflecting more efficient electron transfer. The Ni-containing catalysts also exhibit lower Tafel slopes (121.5 mV/dec for PdNi/OLC and 136.9 mV/dec for PdNi/CeO₂/OLC), indicating improved reaction kinetics due to Ni. Density functional theory (DFT) calculations suggest that Ni incorporation into Pd enhances electron donation, which is enhanced by the CeO₂ support. This synergy improves IPA adsorption and reaction kinetics, leading to enhanced electrocatalytic performance. These findings demonstrate that alloying Pd with Ni and supporting it on CeO₂ significantly boosts electrocatalytic activity, stability, and mass transport in alcohol oxidation. The PdNi/CeO₂/OLC catalyst is a promising candidate for DIFC applications, offering high efficiency, durability, and a low onset potential.