Hydrogen oxidation on ensembles of Pt nanostructures supported on microelectrodes

JOSE LUIS FERNANDEZ; MARIELA A. BRITES HELÚ; MARÍA R. GENNERO DE CHIALVO; ABEL C. CHIALVO

Querétaro

Congreso; 64th Annual meeting of the International Society of Electrochemistry; 2013

International Society of Electrochemistry (ISE)

Thiswork carried out a mechanistic study of the hydrogen oxidation reaction (hor) on platinum nanoelectrodes under well-controlledmass-transport conditions defined on a microelectrode. The elementary kinetic parametersof the Tafel-Heyrovsky-Volmer (THV) mechanism were determined and related tothe nanoelectrode dimensions. Random ensembles of Pt nanostructures weredeposited on gold microelectrodes (disk radius: a = 12.5 mm)by short-pulse sputtering. These nanostructures had a dish-like geometry, withheights h = 1.1 ± 0.2 nm (as measured by STM) and adjustable radii(r) with narrow dispersions. Thefraction of active area (faa)was measured by adsorption and further electro-oxidation of carbon monoxide. Boththe r and faa values of the resulting micro nanoelectrodeensembles (mNEEs) varied in the ranges 1 nm < r < 10 nm and 10-3 < faa < 0.3, respectively, dependingon the sputtering conditions. The horwas analyzed on Pt mNEEsby steady-state current(i)-overpotential(h)curves measured in 0.5 M H2SO4 saturated with H2.The kinetic model to correlate these curves was a modification of that previouslydeveloped for rotating nanoparticle array electrodes, and takes into accountthe mass-transport through two diffusion layers with radial fluxes. The dependenceof the limiting current density (jL)on faa that resulted fromthis model reproduced acceptably well the experimental values, as can be seenin Fig. 1b. Thus, the i(h)dependences were fitted with the equations of the THV mechanism (lines in Fig.1a) to obtain the elementary kinetic parameters.