On the influence of hydronium and hydroxide ion diffusion on the hydrogen and oxygen evolution reactions in aqueous media

• Demonstrating influence of HER and OER on ion diffusion
• OER and HER limited by hydroxide and hydronium ion diffusion
• Measuring diffusion constants of hydroxide and hydronium ions by RDE

We present a study concerning the influence of the diffusion of H+ and OH− ions on the hydrogen and oxygen evolution reactions (HER and OER) in aqueous electrolyte solutions. Using a rotating disk electrode (RDE), it is shown that at certain conditions the observed reaction rates do not depend on the kinetics but on diffusion properties; In fact we demonstrate how studying these reactions in 0.1 M non-buffered aqueous electrolytes with pH-values ranging between pH 1 to pH 13, the diffusion coefficients of H+ and OH− ions can be determined. Within the experimental error limits, we found no pH dependency on the diffusion coefficients for any of the investigated ions.