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.