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 PtRu 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 mol L−1 H2SO4 at 25 °C. The electrocatalytic activity of the PtRu/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.