Examination of the voltage profile during the oxidation of DHA reveals that this compound turns into the DHA dimer at a quite high cell voltage, around 0.9 V. Thus, if the discharge cutoff voltage of a DHAQ | ferro/ferricyanide cell is set at or below this value, then DHA, which forms gradually due to the disproportionation of DHAQ 4-(Scheme 1), may get electrochemically oxidized to the dimer even during regular cycling. Consequently, a mixture of DHA and dimer exists in the negolyte well before the onset of a regeneration step. Thus, we hypothesized that the inefficiency of the regeneration procedures at discharge cutoff voltages of 0.9 V or lower in Figure is related to the gradual decomposition of DHA, the dimer, or both, exacerbated at higher OH -concentrations. The hypothesized decomposition reactions starting from DHA and the dimer are shown by red arrows and labeled as either ( ) or (2) in Scheme 2 and are assumed to be homogeneous chemical reactions. Disproportionation reaction of DHAQ to DHA is also shown by a red arrow. Note this scheme does not intend to show an exhaustive reaction pathway. ) are decomposition reactions hypothesized in this work, and the rest are adapted from Ref. .