All CPE experiments were performed in a divided cell where an ion permeable glass frit and methyl cellulose ion exchange membrane were used to separate the anolyte and catholyte, as described elsewhere. A reticulated vitreous carbon (RVC) electrode and Ag/AgxO QRE were placed in the anolyte compartment, while a graphite rod electrode was placed in the catholyte compartment. The Ag/AgxO QRE was placed in a glass capillary filled with DMF/0.1 M TBAP and was separated from the anolyte solution by a glass frit. Glacial acetic acid (0.5 mL of 17 M to give 0.4 M acetic acid in DMF/0.1 M TBAP) was added to the catholyte compartment, enabling the hydrogen evolution reaction to serve as the cathode half-reaction.