Kinetic study of the hydrogen electrode reaction on a porous material in a flow cell

The present work deals with the determination of the electrocatalytic activity of porous electrodes.This problem cannot be appropriately treated with the conventional methods because the reaction is not uniform in the whole electrodic surface.Therefore, it is proposed the evaluation of the variation of the equilibrium polarization resistance with pH.As the current - potential dependences are obtained around the equilibrium condition, current values are very low, gaseous evolution is negligible and the ohmic effects can be avoided through a suitable electrolyte solution.In this context a simple model of a porous electrode was developed, consisting in a tubular electrode operating with a laminar flow of electrolyte, where the mass transfer processes towards and/or from the electrode surface are clearly defined as a function of the mean flow rate of the electrolyte.This method was applied to the study of the hydrogen electrode reaction.The experimental determinations were carried out in a flow cell with a platinum tubular electrode and a regulation of the electrolyte flow saturated with hydrogen gas.The apparent polarization resistance was calculated at different flow rate and pH.The application of the flow model together with a kinetic formalism corresponding to the Volmer - Heyrovsky - Tafel mechanism allowed the evaluation of the intrinsic electrocatalytic activity