The carbon electrode used in this study was a commercial
carbon aerogel obtained from Marketch (Port Townsend,
WA). For characterization, scanning electron microscope
(SEM) image was collected on a JEOL, Inc., JSM-7401F
electron microscope. A surface and pore size analyzer
(TriStar II 3020, Micromeritics Inc., USA) was employed
to obtain the nitrogen adsorption–desorption isotherm,
pore size distribution, and specific surface area via the
Brunauer–Emmett–Teller (BET) method from the nitrogen
adsorption data in the relative pressure range of p/p0 = 0.99.
The pore size distribution curve was derived from the
adsorption branch of the isotherm based on the Barrett–
Joyner–Halenda (BJH) method.