The conductivity of NaCl was measured by a conductivity meter (Thermo Scientific STAR A212 Star A212 Conductivity Benchtop Meter) (Fig. ). The high frequency resistance of the threechamber cell was measured with PEIS (Fig. ). Ohmic resistance of the cell (from PEIS) shows a nearly linear relationship versus center chamber ionic resistance. Because the membrane resistance can go up when using high concentration salt solution, we chose 1 -2 M NaCl as the center chamber electrolyte concentration for further tests. Effect of operation temperature (Fig. )