Figure 5.

Results of long-term electrolysis (hydrogen evolution from a HClO₄/NaClO₄ electrolyte solution) measured by iRDE&GC. Currents measured electrochemically (full black curve) and chromatographically (calculated using eq 1, dots) at E = −625 mV vs Ag|AgCl are shown in (a). A slow drift (decay) over time can be observed as a result of the electrolysis becoming exhaustive. Values of pH measured before and after the electrolysis, along with limiting currents estimated using the respective H⁺ concentrations and the diffusion coefficient of 8.79 × 10^–5 cm² s^–1 are shown by the dashed horizontal lines. This pH change is in alignment with the shifting of the LSV plateaus shown in (b) and also corresponds to the estimated H⁺ concentration change calculated by taking into account the charge of the electrolysis, shown as the hatched area in (a), and a cell volume of 87 cm³. The applied rotational rate was 1600 min^–1, and the linear sweep voltammograms were recorded at a sweep rate of 50 mV s^–1.