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. (C) 2015 Elsevier Ltd. All rights reserved.