Fe(Bhmbpy)3 electrolyte was prepared by dissolving FeCl2 and Bhmbpy with a ratio of 1:3.5 in 1 M NaCl, using HCl adjusting pH to 2, if not claimed otherwise. FeCl2 electrolyte was prepared by dissolving 2 M FeCl2 in water, with NaCl and HCl adjusting the whole ion concentration and initial pH to 2.