Separation ofthe partial currents for reduction of hydronium ion and water in dilute strong acid solutions using the sinusoidal hydrodynamic modulation method

The simultaneous mass-transport controlled reduction of hydrogen ions and charge-transfer controlled reduction of water has been studied in 1 M KCl solutions of dilute strong acid. Using the sinusoidal hydrodynamic modulation technique, SHM, at a rotating disk electrode, RDE, these studies confirm the existence of a thin reaction layer at the electrode surface where the neutralization reaction between H⁺ and OH^- produced from water reduction causes a decrease in the limiting flux of hydrogen ions at the electrode. An approximate solution to the convectiye-diffusion problem has been obtained, as has the decrease in modulation current response and the thickness of the reaction boundary layer, δ_r- The negligible distortion in the conventional convective-diffusion limiting RDE current accompanying the parallel processes is explained by the magnitude of °_r. Separability of the mass-transfer and non-mass transfer controlled components by the SHM method is demonstrated with studies at various applied potentials, modulation amplitudes and frequencies.