Synthesis and characterization of PtCo nanowires for the electro-oxidation of methanol

Abstract

PtxCo100−x (60≤x≤100) 1D nanostructures (nanowires) on titanium are prepared by direct electrodeposition throughout a porous anodic aluminum oxide membrane and analyzed for methanol electrooxidation. For comparison, thin films of the same composition are also prepared. The morphology and composition are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A model based on the simultaneous deposition of Pt and Co underpotential deposition (UPD) on Pt was devised to understand how the composition varies with the electrodeposition potential. The deposition rates were determined by means of an Electrochemical Quartz Crystal Microbalance (EQCM). PtxCo100−x alloy formation was confirmed by X-ray diffraction (XRD). Electrocatalytic properties for methanol oxidation are investigated by cyclic voltammetry (CV) in 1.0M CH3OH+0.5M H2SO4. The results show that PtCo nanowires yield to an enhancement (by a factor of 5) of the exposed surface area (m2g−1). In the presence of CH3OH, If/Ib ratio of Pt rich nanowires is systematically higher than for thin films with the same composition. If/Ib ratio of Pt90Co10 nanowires is 1.59, larger than that of pure Pt (If/Ib=0.76–0.87) and commercially available PtCo deposited on carbon support (If/Ib=1.32).