The influence of three groups of Pt-Ru/C catalyst's precursors on its performance for direct methanol fuel cell

This research is aimed to increase the activity of platinum-ruthenium alloy (Pt-Ru/C) catalysts and thus to lower the catalyst loading in anodes for methanol electrooxidation. The direct methanol fuel cell (DMFC) anode catalysts, Pt-Ru/C, were prepared from three groups of precursors by thermal reduction. The phase structure, particle size, size distribution and the morphology of reduced catalysts were determined by means of high-resolution transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that XRD patterns of all the catalysts show Pt reflexion of a face centered cubic (fcc) crystal structure. But there are diffraction peaks indicating the presence of either pure Ru or Ru-rich hexagonal close packed (hcp) phase, which is not alloyed with Pt in Pt-Ru/C catalysts prepared from (NH₄) ₂PtCl₆+Ru(OH)₃, or H₂PtCl ₆+RuCl₃ as precursors. The catalyst prepared from Pt (NH₃)₂ (NO₂)₂ and Ru compound of self-prepared as precursors had a more homogeneous distribution of Pt-Ru alloy in carbon and a small particle size of about 3.7 nm. Their performance was tested using a glassy carbon working electrode by cyclic voltammetry(CV), chronoamperometric and amperometric i-t curves in a solution of 0.5 mol· L^-1 CH₃OH and 0.5 mol·L^-1 H ₂SO₄ at 25°C. The electrocatalytic activity of Pt-Ru/C catalysts prepared from Pt(NH₃)₂(NO₂) ₂ and Ru compound of self-prepared as precursors has the highest catalyticactivity for methanol electrooxidation. The peak current density in CV is 11.5 mA·cm^-2.