The three-electrode measurements were conducted in a Swagelok cell as shown in SI Figure . Two identical carbon electrodes (YP50F, 1/4-inch diameter) were used as the working and counter electrodes, with two separator disks (GF/A Whatman, 5/16-inch diameter) placed in between the electrodes. The cell was assembled horizontally in the Swagelok cell (Figure ). For the electrochemistry measurements in air, 1 M Na2SO4 (aq) (750 µL) was added and then the Hg/HgO reference electrode was submerged in the electrolyte from the top input (Figure ). The supercapacitor was precycled by conducting 20