The formation of LMB might be the reason of bleaching at −1.0 V during bulk electrolysis. Finally, electron exchange rate was determined at −0.7 V. At intermediate times (50–100 ms), the current was dominated by the rate of the electron cross exchange (Re) between the Pt redox sites and MB molecules. According to the method described in the literature [29], the rate of electron exchange (Re) between the electrode surface and MB molecules was calculated as per the following equation:
equation(8)
Ic/Id = (πRe [MB+] t)1/2
where, Ic is the catalytic current in the presence of MB+, Id is the diffusion limited current in absence of MB+ and t the time. The inset of Fig. 7 shows the Ic/Id versus t1/2 curve in the −0.7 V. From the slope, the value of Re was determined to be 8.3 × 107 L mol−1 s−1. Based on all experimental data, a scheme of bleaching of MB molecules has been proposed in Scheme 1.