Figure shows a typical current-time (i-t) trace for the mediated oxidative reduction of 4-BrBN. Prior to the beginning of bulk electrolysis, 20 mL of a DMF solution containing 0.1 M TBAP and 1.0 M H2O (i.e., the solvent composition is 19.64 mL DMF and 0.36 mL H2O) was deaerated with Ar gas for 30 min to remove any dissolved O2. Throughout the entirety of all CPE experiments, an Ar atmosphere was maintained over the solution headspace (Note: this CPE is air sensitive as CO2 •-can reduce O2 to O2 •-). Following the removal of O2, a potential of 0.0 V vs Fc/Fc + was applied to the RVC anode, at which point a small charging current is observed, denoted by point (A) in Figure . Upon stabilization of the current to a steady baseline, 1 mL of deaerated solvent was removed from the anode compartment and was used to dissolve 4-BrBN (4 mg, 0.02 mmol). The concentrated 4-BrBN solution was then injected into the anode compartment, point (B) in Figure . As expected, no change in current is observed, demonstrating that 4-BrBN is not electroactive at 0.0 V. After 45 min, 2 mL of deaerated anolyte was removed from the cell, into which to DiMeFc (4 mg, 0.02 mmol) and (TEA)2C2O4 (52 mg, 0.15 mmol) were dissolved. This concentrated solution was injected back into the anode compartment at point (C) in Figure , resulting in a large anodic current spike. After approximately 2 h, the current returned to its original baseline value, point (D), indicating conclusion of the electrolysis. Liquid-liquid extraction was used to isolate the resulting reaction products, which were analyzed by ultra-high-performance liquid chromatography/mass spectrometry (UHPLC/MS) and gas-chromatography/mass spectrometry (GC/MS) (see Supporting Information for additional details). Results for the oxidative reduction of 4-BrBN with five different DMF/H2O solvent compositions are shown in Table . High conversion yields are achieved in the presence of 0, 1, and 2 M of H2O (entries 1-3), while poor conversion yields are obtained in the presence of 4 and 8 M H2O (entries 4 and 5). When 1 M H2O is present in the solution, a 95% conversion yield is obtained, representing the approximate optimal solution condition for the oxidative reduction of The results in Table qualitatively agree with the hypothesis put forth from CV studies that the efficiency of the oxidative reduction of 4-BrBN is predictably tuned by additions of H2O.