Voltammetric currents of the reduction of hydrogen ions from monoprotic acids. The effect of water dissociation

In the present work we report on the results of numerical simulation of the voltammetric currents of the hydrogen ions reduction from aqueous solutions of monoprotic acids. Diffusion and migration of the components of solution are taken into account, as well as homogenous chemical reaction of water dissociation. Calculations show that for small overvoltage the rate of the electrode reaction of hydrogen ion reduction is close to that in binary solutions. For large overvoltage, the rate of hydrogen reduction is higher than it might be expected for a binary acid. The concentration of the hydroxyl ion near the electrode substantially exceeds its concentration in the volume and has a maximum at a small distance from the metal surface. These effects result from the joint action of migration and a fast chemical reaction of water dissociation. In aqueous solutions of a strong acid with an excess of the supporting electrolyte, the effect of water dissociation reaction on the rate of hydrogen ion reduction is insignificant.