Another set of electrolysis were also performed applying negative potentials using KNO3 as supporting electrolyte. However, at −1.0 V, MB molecules were decolorized moderately at the working electrode (k: 7.5 × 10−3 min−1) irrespective of electrolyte. The spectral changes (duration 90 min) of MB molecules, in the presence of KNO3, have been displayed in Fig. 5. The decrease of color at the working electrode at sufficiently high negative potentials was obviously due to some heterogeneous electron transfer reactions but which did not cause the breakdown of the MB molecules.