We performed cyclic voltammetry (CV) on a freshly prepared aqueous BQ solution in a pH = 6.6, 100 mM KCl electrolyte (Figure ; See Experimental Methods in the Supplementary Information). We observed a reduction peak at approximately -430 mV vs. Ag/AgCl (-233 mV vs standard hydrogen electrode (SHE)) and a single oxidation peak near +230 mV vs. Ag/AgCl (+427 vs SHE). The reduction peak possibly represents BQ electroreduction to quinone dianions, which occurs at a potential of -286 mV vs. SHE . The oxidation peak is likely a combination of QH2 oxidation and BQ oxidation. The latter corresponds to conversion of BQ to organic acids and humic substances, which prior works have demonstrated occurs near a potential +300 mV vs. SHE . We note that factors including electrode material and electrolyte lead to differences between the potentials measured here and literature values. The oxidation is catalyzed by metal oxides, such as tin, lead, or iridium oxide . The formation of organic acids and humic substances was confirmed by mass spectrometry measurements of oxidized BQ solutions (Figure ). Several prior works have shown that electrochemical BQ reduction causes pH increases near the cathode . We subjected a 10 mM BQ solution in 1 mM KCl between two ITO electrodes to repeated applications of a multimode electric potential consisting of a 2 V amplitude, 400 Hz oscillatory potential offset by a -200 mV steady potential (Figure ) and measured the resulting pH change near the cathode using a pH-sensitive fluorophore, fluorescein (Figure ;