Preparation of Nanostructured/ Microplatinum Surfaces by Application of a Square Wave Potential Regime for Methanol Oxidation

Abstract

Platinum nanoparticles were electrodeposited on the tantalum electrode by using a square wave potential regime to form a modified electrode. The modified electrode was characterized by scanning electron microscopy (SEM), cyclicvoltammetry and energy-dispersive X-ray spectroscopy (EDX). The size, shape, and uniformity of the distribution of particles are influenced by frequency, lower and upper limits, time application of the square wave potential regime, and the concentration of [PtCl6]2- in the solution. The optimal deposition time to obtain platinum nanoparticles on the tantalum surface was 2 min. The optimal conditions for preparation of the nanostructured platinum deposits were 100 Hz frequency, -0.4 V to 0.00 V lower and higher limits of the square wave respectively with an amplitude of 0.4 V. The optimal concentration was 1x10-4 M [PtCL6]2-. The electrocatalytic properties of platinum nanoparticles deposited onto the tantalum substrate were investigated for oxidation of methanol in acidic medium. The modified electrode by nanoparticles showed enhanced electrocatalytic performance compared to the polycrystalline platinum electrode. The sizes of the studied Pt nanoparticles range from 11 to 89 nm, polycrystalline Pt is inferior to nanoparticles Pt for methanol oxidation at above 65.1 mV, and the oxidation current on nanoparticles Pt becomes much higher than that on polycrystalline Pt at above 35μA.The peak current density ratios (jf/jb) for the polycrystalline pt and nanoparticles Pt electrodes were 1.01 and 1.87, respectively, indicating that the nanoparticles Pt electrode was much more resistant to catalytic poisoning.