Kinetics of hydrogen evolution reaction with Frumkin adsorption: re-examination of the Volmer–Heyrovsky and Volmer–Tafel routes

Abstract A re-examination of the basic kinetic derivations of the Volmer–Heyrovsky and Volmer–Tafel routes for the hydrogen evolution reaction with a Frumkin adsorption of the intermediate was carried out. Expressions for the dependence of the surface coverage and current density on overpotential were derived for both routes without kinetic approximations. On the basis of these dependencies, the kinetic behavior was simulated for different values of the parameters involved at 298.16 K. Conditions for the existence of Tafelian domains were discussed and the independence of the Tafel slopes on the type of adsorption of the reaction intermediate was demonstrated. The results obtained were critically compared with those derived from approximated expressions customarily used and the differences with them were pointed out.