As observed in our results, the direction of the photocurrent generation is flipped upon moving from -1V to -0.5V, thus implying a different mechanism. Moreover, unlike at -1V, at -0.5V we observed the emergence of a new reduction peak. Accordingly, we suggest here that in the -0.5V bias regime, the charge transfer at the electrode/electrolyte interface is the reaction ratelimiting process (Figure ). Upon light irradiation, the RO -••• H + ion pairs are formed, resulting in the attraction of H + toward the negatively charged cathode followed by their reduction, which eventually increases the cathodic current.