Kinetic Model of Hydrogen Evolution at an Array of Au-Supported Catalyst Nanoparticles

A model is presented for studying the electrocatalytic activity at an array of catalyst nanoparticles that is deposited on a catalytically inactive support material. The objective is to rationalize effects on apparent reactivity of sizes and packing densities of nanoparticles. In the current version, the focus of the model is on the contribution of the spillover effect of adsorbed hydrogen to the overall rate of the hydrogen evolution reaction. For nanoparticles of fixed size, the current density per catalyst surface area exhibits a peculiar maximum as a function of the surface particle density; the optimum particle density varies with the rate of spillover of adsorbed hydrogen from particle to support and with adsorbate surface diffusion. For fixed particle density, the current density per catalyst surface area increases strongly with decreasing particle size. The model was used to fit experimental current densities for different catalyst particle coverage at varying electrode potentials. A good agreement between experimental data and calculated results was found. The fits provide key parameters of surface processes on the catalyst/support system.