2.6. HER Studies in NaHCO3 and NaOH

For direct comparison with RRDE experiments, HER studies were done in Ar saturated 0.1 M NaHCO₃ electrolyte; for this experiment, a RHE reference and a RDE tip were used. The working electrode was prepared according to subsection 2.3. The CVs were taken in the potential window of 0 to −1 V vs RHE at a scan rate of 25 mV s^–1 at different rotation speeds. Additional studies were also done at different bicarbonate concentrations (0.025, 0.05, 0.2, 0.4, and 0.5 M) by following the same procedure as above.

In order to study the role of pH on water reduction reaction, further studies were done at pH 10, 11, 12, and 13 by using NaOH, where the ionic strength of the electrolyte was maintained at 0.1 M by adding NaClO₄. This was done in order to eliminate any effects from the cation concentration changes in the bulk and to have a comparable ionic strength with the experiments done in NaHCO₃. In these studies, the CVs were taken in the potential window of 0 to −0.8 V vs RHE at a scan rate of 25 mV s^–1, at 2500 rpm.