According to Figure , the conversion of DHA to DHAQ is incomplete at a regeneration cutoff voltage of 0.0 V. Whereas a conversion efficiency of almost 80% is achieved in 2.0 M OH -, the efficiency in 1.0 M OH -is only 65% at 0.0 V regeneration cutoff. Lowering the cutoff voltage to -0.1 V, i.e. reverse-polarizing the cell, raises the conversion efficiency. The dependence of the conversion efficiency on cutoff voltage is more intense in 1.0 M OH -. This figure corroborates the implication from Figure that some amount of dimer decomposition is inevitable and a conversion of 100% does not seem attainable. Figure also shows that lowering the cell regeneration cutoff voltage below -0.1 V does not improve the conversion efficiency. As shown in Figure , applying a very negative cell voltage (-0.4 V) may lead to the formation of undesired species.