The influence of acidic and alkaline precursors on Pt-Ru/C catalyst performance for a direct methanol fuel cell

This research aims to increase the activity of platinum-ruthenium alloy (Pt-Ru/C) catalysts for methanol electrooxidation. The direct methanol fuel cell (DMFC) anodic Pt-Ru/C catalysts were prepared from acidic and alkaline Pt(NH3)(2)(NO2)(2) solutions as Pt precursors, respectively, and with the same acidic Ru compound but without Cl- ion as the Ru precursor by thermal reduction. The phase structures, lattice parameters, particle sizes, alloy composition, distribution, and the morphology of reduced catalysts were determined by means of X-ray diffraction (XRD), energy-dispersive analysis of X-ray (EDAX), and high-resolution transmission electron microscopy (TEM). It was found that the XRD patterns of the two catalysts showed Pt reflections for a face centered cubic (fcc) crystalline alloy structure. The catalyst prepared from the acidic Pt(NH3)(2)(NO2)(2) as a precursor has a more homogeneous distribution of Pt-Ru metal particles on carbon. Its size is relatively small, about 3.7 nm. Its chemical composition is quite similar to theoretical value of 1:1 (Pt:Ru). The catalyst prepared from the alkaline Pt(NH3)(2)(NO2)(2) as a precursor has an uneven distribution of Pt-Ru particles on carbon and its size is relatively large, and the chemical composition of Pt and Ru was 6:4. The performance was tested using a glassy carbon working electrode by cyclic voltammetry (CV) and chronoamperometric curves in a solution of 0.5 mol L-1 CH3OH and 0.5 moI L-1 H2SO4 at 25 degrees C. The electrocatalytic activity of the Pt-Ru/C catalyst prepared from the acidic Pt(NH3)(2)(NO2)(2) as a precursor was the higher for methanol electrooxidation than that of catalyst from the alkaline source. The peak current density from the CV plot was 11.5 mA cm(-2). (c) 2006 Elsevier B.V. All rights reserved.