For the results reported in Figure , the electrochemical oxidations were performed under a constantcurrent (CC) step followed by a constant-voltage (CV) step to exclude the impact of cell internal resistance changes on the extent of the reaction completion . The CC step was usually set at a current density of 2 mA/cm 2 to force a slow oxidation reaction for both DHA and the dimer. To explore whether the oxidation rate affects the conversion efficiency, oxidation was performed an order of magnitude more rapidly at a current density of 20 mA/cm 2 . With such a change, in 2.0 M OH -and a cutoff voltage of -0.1 V, the conversion efficiency remained almost unchanged. However, at a cutoff voltage of -0.2 V, the conversion efficiency decreased to 84% at 20 mA/cm 2 from 89% at 2 mA/cm 2 . Although this variation is quite small, such a decline may further confirm the adverse effect of a very low cutoff voltage on the conversion of DHA to DHAQ. This observation, which seems consistent with the slight decline in the conversion shown in Figure in 2 M OH -at cutoff voltages lower than -0.1 V, may be explained as follows. Under slow DHA/dimer oxidation, most of the reaction occurs in the CC region at a voltage above the cutoff value; see, e.g., Figure . At a faster DHA/dimer oxidation rate, however, the cell voltage quickly approaches the cutoff voltage. If the main electroactive species, DHAQ in this case, is unstable at very low cell voltages as indicated by Figure , then more DHAQ may decompose when the cell spends longer at lower voltages during the faster oxidation rate. Although the cutoff voltage for the results shown in Figure is -0.4V, DHAQ may decompose to a lesser extent at cutoff voltages explored in Figure . We interpret these results to mean that the rate of oxidation of DHA does not adversely affect the conversion efficiency as long as the cutoff voltage is not harmful to the main reactive species. This safe cutoff cell voltage appears to be closer to -0.1 V, i.e. a negolyte voltage of 0.45 V vs. SHE. Thus, the conversion of DHA to DHAQ can be performed faster only if the cutoff voltage is chosen properly.