Electrocatalytic Activity of Core-shell Au@Pt Nanoparticles for the Hydrogen Oxidation Reaction

M.A. MONTERO; M.R. GENNERO DE CHIALVO; A.C. CHIALVO

Niza

Congreso; 61st Annual Meeting of the International Society of Electrochemistry (ISE); 2010

International Society of Electrochemistry

The objective of the present work is to prepare core-shell Au@Pt nanoparticles and evaluate their electrocatalytic activity for the hydrogen oxidation reaction. The Au nanoparticles were prepared by the citrate method, which average size measured by STM was 14.2 nm. Then, they were covered with platinum through the reduction of H2PtCl6 with hydroxylamine. The further observation by TEM gave an average particle size of 15.1 nm. This result allows inferring that the average thickness of the layer of platinum on the gold nanoparticle is about 0.5 nm. To prepare the working electrode, a drop of the colloidal solution (5 µl) was placed on the substrate and then evaporated in a desiccator. The amount of nanoparticles can be controlled by repeating this operation several times as well as by diluting the original solution. Thus it can be prepared electrodes with a very low factor of active area. The substrate consisted in a smooth gold rod mounted in a Teflon cylinder to be used as a rotating disc electrode. The electrodes thus prepared were characterized by cyclic voltammetry and then evaluated as electrocatalysts for the hydrogen oxidation. The experimental measurements of the current-overpotential dependencies were carried out in 0.5 M H2SO4 at a rotation rate of 2500 rpm and on steady state by the application of a potential program. These experimental curves were correlated with kinetic expressions previously derived on the basis of the Volmer-Heyrovsky-Tafel mechanism. It was found that at low factors of active area the kinetics of the hydrogen oxidation on the Au@Pt nanoparticles displays a transition between the Tafel-Volmer route, which dominates at low overpotentials, and the Heyrovky-Volmer route, predominant at high overpotentials.