In situ pH measurements with hydrous iridium oxide in a rotating ring disc configuration

► In situ pH measurements were successfully performed using an RRDE configuration. ► Hydrous iridium oxide was used as the pH sensing material on the ring. ► The response time of the ring, limits the applicability in transient experiments. ► Steady state measurements are most suitable, owing to the ring response time. ► To account for non-idealities, an experimental “collection efficiency” is advised.