Promoting effect of (Co, Ni)O solid solution on Pd catalysts for ethylene glycol electrooxidation in alkaline solution

Abstract

In order to enhance the catalytic activity of Pd-based catalysts in the electrooxidation of ethylene glycol, CoO-NiO binary oxides were designed and synthesized as supports for Pd nanoparticles. The physicochemical properties of the prepared catalysts were investigated by XRD, XPS and HR-TEM, and the electrochemical performances of the catalysts were analyzed by cyclic voltammetry (CV), chronoamperometry (CA), linear sweep voltammetry (LSV), Tafel curve and electrochemical impedance spectroscopy (EIS). The results indicate that the significantly improved electrocatalytic activity and stability in alkaline medium for Pd/CoO-NiO/C catalyst due to the well dispersed Pd nanoparticles and the synergistic effect of (Co, Ni)O solid solution. It is highlighted that Pd/CoO-NiO/C catalyst exhibits a higher mass peak current density (2980.83 mA mg−1Pd) than that of Pd/CoO/C (2373.75 mA mg−1Pd) and Pd/C (1633.75 mA mg−1Pd). Moreover, the physical origin of the improved electrocatalytic activity has been unraveled by first-principle calculations. Notably that, Pd4/CoO-NiO(111) catalyst exhibits more negative CO adsorption energies Eads and provides more electrons during the CO adsorption process compared with Pd4/CoO(111), which well explains experimental results. These results support that Pd/CoO-NiO/C catalysts have high potential for direct alcohol fuel cells application.