Electrocatalytic oxidation of formic acid by Pt/Co nanoparticles

The electrocatalytic activity of Pt/Co bimetallic nanoparticles towards for mic acid (0.2 M HCOONa/0.28 M HClO4) oxidation was explored by cyclic volta mmetry of the nanoparticles supported on highly oriented pyrolytic graphite (HOPG). The particles were prepared by electrodeposition from a bath of mi xed concentrations of Co2+ and PtCl62- ions and characterized by tapping mo de atomic force microscopy (TMAFM). The compositions of the nanoparticles w ere determined as close as possible to individual particles by energy dispe rsive X-ray analysis (EDX). Nanoparticles of different atomic ratios of Pt/ Co were prepared and the peak currents in cyclic voltammetry of formic acid oxidation were measured. The activity of the bimetallic particles was foun d to be maximum when the atom ratio Pt:Co is between 1 : 1.1 and 1 : 3.5. T he maximum activity is about one order of magnitude higher than that of pur e Pt nanoparticles. Comparison of the currents to those from microelectrode s and wire electrodes shows no mass-transfer limitations in nanoparticles w ith diameters less than 100 nm. The bimetallic particles exhibit interestin g kinetics and Co appears to significantly enhance the electroxidation of f ormic acid. The advantage of using nanoparticles for mass-transfer free kin etics studies is also demonstrated.