Promising ethylene glycol electro-oxidation at tailor-designed NiOx/Pt nanocatalyst

Abstract

The significant hydrogen content and energy density in addition to the liquid nature and the high boiling point of ethylene glycol (EG) have recommended it as a potential replacement for hydrogen in proton exchange membrane fuel cells (PEMFCs). We herein report an enhanced electrocatalytic activity of EG electro-oxidation (EGO) in alkaline medium on a binary catalyst composed of platinum nanoparticles (nano-Pt) and nickel oxide nanoparticles (nano-NiOx) and assembled electrochemically on a glassy carbon (GC) electrode. The electrocatalytic activity of this catalyst towards EGO depended significantly on the loading level of the constituting ingredients of the catalyst, electrolyte acidity (pH) and the operating temperature. Several tools of electrochemical and materials characterization including the cyclic voltammetry (CV), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were all employed to confirm the successful deposition, to probe the relative ratio of the catalyst's ingredients and to evaluate the surface topography, bulk composition and structure of the proposed catalyst. The results indicated a volcano-shaped dependence of the catalytic activity towards EGO on the loading level of nano-pt and nano-NiOx in the recommended catalyst. The investigation succeeded to optimize the synthetic procedure to reduce the amount of the precious Pt in the catalyst while maintaining a better catalytic activity than that obtained at the bare Pt surfaces. Interestingly, adding nano-NiOx to the catalyst's ingredients (NiOx/Pt/GC) ended up with a significant lowering (13.90 kJ mol−1) in the activation energy (Ea) of EGO in comparison to that (Ea = 18.83 kJ mol−1) obtained at the Pt/GC electrode.