Hydrogen Oxidation on ensembles of Pt nanostructures supported on microelectrodes

J.L. FERNANDEZ; M.A. BRITES HELU; M.R. GENNERO DE CHIALVO; A.C. CHIALVO

Queretaro

Congreso; 64th Annual Meeting of the International Society of Electrochemistry (ISE); 2013

ISE

This work carried out a mechanistic study of the hydrogen oxidation reaction (hor) on platinum nanoelectrodes under well-controlled mass-transport conditions defined on a microelectrode. The elementary kinetic parameters of the Tafel-Heyrovsky-Volmer (THV) mechanism were determined and related to the nanoelectrode dimensions. Random ensembles of Pt nanostructures were deposited on gold microelectrodes by short-pulse sputtering. These nanostructures had a dish-like geometry and adjustable radii with narrow dispersions. The fraction of active area (faa) was measured by adsorption and further electro-oxidation of carbon monoxide. The radius of the resulting micro nanoelectrode ensembles (MNEEs) varied between 1 nm and 10 nm and faa between 10-3 and 0.3, depending on the sputtering conditions. The hor was analyzed on Pt MNEEs by steady-state current-overpotential curves measured in 0.5 M H2SO4 saturated with H2. The kinetic model to correlate these curves was a modification of that previously developed for rotating nanoparticle array electrodes, and takes into account the mass-transport through two diffusion layers with radial fluxes. The dependence of the limiting current density on faa that resulted from this model reproduced acceptably well the experimental values. Thus, the current density-overpotential dependences were fitted with the equations of the THV mechanism to obtain the elementary kinetic parameters.