Electro-oxidation competency of palladium nanocatalysts over ceria-carbon composite supports during alkaline ethylene glycol oxidation

Abstract

Direct alcohol fuel cells (DAFCs) are widely regarded as one of the most promising among the futuristic and capable energy systems; direct liquid fuel cells (DLFCs). In this article, we discuss in detail the competency of palladium nanoparticles developed over carbon-ceria composite supports (Pd/C-CeO2) as efficient and durable anode catalysts for the alkaline electro-oxidation of ethylene glycol (EGOR). For the first time, a systematic assessment of the EGOR performance of palladium catalysts with varying Pd-ceria ratios has been reported. The scalable solid-solution route reduction technique enabled the processing of Pd nanoparticles with controlled morphology, size and excellent CeO2 interaction. The structural features of the prepared catalysts were studied using X-ray diffraction, electron microscopy (TEM) and X-ray photon spectroscopy techniques, while the electrochemical performance of the catalysts was analyzed using cyclic voltammetry and chronoamperometry. During alkaline EGOR, the Pd/C-CeO2 catalysts showed an enhanced current density (as high as 68.5 mA cm-2), more negative onset potential, excellent mass activity (4.6 A mg-1Pd) and exceptional durability compared to Pd/C. The enhanced alkaline EGOR kinetics of the Pd/C-CeO2 catalysts is well attributed to the promotion effect of CeO2 on Pd by creating more Pd-OHads and also improved tolerance to poisoning species on the Pd surface. Further, the enhanced ECSA of Pd/C-CeO2 has also aided the excellent EGOR activity in alkaline medium. The validated enhanced oxidation ability of these Pd/C-CeO2 catalysts for the anodic oxidation of other low molecular weight alcohol fuels including methanol and ethanol showcased their application potential toward DMFCs and DEFCs.