Kinetics of CO₂ electroadsorption on electrodispersed platinum electrodes in acid solutions

Abstract

The kinetics of CO₂ electroadsorption on electrodispersed Pt electrodes have been investigated in different acid electrolytes. The kinetic data obtained at different adsorption potentials, adsorption times and CO₂ concentrations in solution have been interpreted in terms of two complex reaction mechanisms involving the formation of strongly and weakly bound reduced CO₂ adsorbates through reactions involving s-H and w-H adatoms, respectively, and carbon dioxide. The reaction mechanism between H adatoms and CO₂ implies the initial electroadsorption of H atoms, the transport of CO₂ from the bulk of the solution to the reaction interface, and the formation of the reduced CO₂ adsorbate. Under certain conditions, particularly when s-H adatoms are involved, the entire reaction approaches mass transport rate control. Conversely, the reaction between w-H adatoms and CO₂ appears as a rather slow process.