We assembled a supercapacitor cell with one donor side solution with high concentration of acid or base and another side of initially neutral pH as acceptor. We monitored the pH of both sides. The source side pH did not have significant change after two days of applied current (state range of applied currents). Therefore, the crossover flux was calculated with the acceptor side pH change. pH value was converted into concentration, and then the concentration rate of change was normalized by the acceptor side solution volume (V) and the membrane area (Amem).