Rotating Nanoparticle Array Electrode as a Tool for Steady State Kinetic Studies

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 kinetic study of an electrode reaction requires the experimental determination of the activated reaction rate, free from any limitation due to mass transfer of reactants and/or products. From a theoretical point of view, the ideal condition should be that in which the limiting diffusion current density (jL) tends to infinity. This condition cannot be achieved experimentally, but significant increases of jL values can be obtained through an adequate design of the measurements. To take into account these aspects, as well as to evaluate the electrocatalytic activity of metallic nanoparticles, the present work proposes the use of an electrode consisting in an array of nanoparticles dispersed on the surface of a conducting inert substrate, which is subjected to rotation in order to ensure that a steady state condition for the reaction under study is reached. The preparation of such electrodes is feasible, but for the analysis of dependence of the current density (j) on overpotential (h) at a given rotation rate (w), it remains the problem of the lack of an expression that establishes a relationship between the limiting diffusion current density and the geometric parameters of the array. Consequently the present work developes a model involving the nanoparticle radius (r) and the average distance between the particles (d). It was also defined the active area factor (faa) that takes into account the difference between the diffusion flow area (geometric area) and the real active area. The resulting expression was applied to the case of hydrogen oxidation reaction reaction (hor), resolved under the kinetic mechanism of the Tafel-Heyrovsky-Volmer, which expressions for the j(h) dependences were previously derived.