In this section, we shift from having a PA in the single cell configuration to having a PB in this configuration. As before, we first identified the electrochemical reactions of the 6AQ PB by CV measurements in dark and under UV irradiation (Figure ). The unique electrochemical feature that appears under light irradiation is a negative peak with a maximum around -1V that is absent in the dark. Unlike the case of having a PA in the solution, here, having a PB resulted in the increase of cathodic current upon the irradiation of 6AQ at the negative (-1V) bias regime (Figure ). Accordingly, while measuring the CA at this potential, we observed an increase in cathodic current with an absolute measured photocurrent density of 0.05±0.01 µA/cm 2 (Figure ). Upon turning off the irradiation, the current density returned back to the baseline level. In line with the mechanism suggested for the PA under the applied bias of -1V (Figure ), here the rection rate is limited by mass transfer (Figure ). However, since the PB is uncharged prior to the irradiation, it is not depleted from the negatively charged electrode.