Effect of Ni on PtRu/C catalyst performance for ethanol electrooxidation in acidic medium

This research is aimed to improve the utilization and activity of anodic catalysts for ethanol electrooxidation. The direct ethanol fuel cell anodic catalysts, PtRuNi/C and PtRu/C, were prepared by chemical reduction method. Their performances were tested by using a glassy carbon disk electrode through cyclic voltammetric curves, chronoamperometric curves, and amperometric i-t curves in a solution of 0.5 mol/L CH₃CH₂OH and 0.5 mol/L H₂SO₄. The particle size, lattice parameter, composition, micro-morphology, and surface states of metals in the PtRuNi and PtRu surface particles were determined by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX) analysis, transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS), respectively. XRD analysis showed that both of the catalysts exhibited face-centered cubic structures and had smaller lattice parameters than did Pt/C catalyst. Their sizes are relatively small, about 3.0 nm. Their size distribution of the metal nanoparticles is very homogeneous, without evident agglomeration. There are a lot of Ni oxides with different oxidation states in the PtRuNi/C catalyst from XPS results. No significant differences in the ethanol electrooxidation on both electrodes were found regarding the onset potential for ethanol electrooxidation by using cyclic voltammetry. Yet, the catalytic activity of the PtRuNi/C catalyst is much higher for ethanol electrooxidation than that of the PtRu/C catalyst. Also, its CO-tolerance is better than that of the PtRu/C catalyst. The hydrogen spillover effect of Ni hydroxides and electronic effect of metallic Ni play an important role in the catalytic performance of PtRuNi/C catalyst for ethanol electrooxidation.