Effect of the carbon microporous structure on the capacitance of aqueous supercapacitors

Abstract

Using a combination of cyclic voltammetry experiments and molecular dynamics simulations, we study the effect of microporous carbon structure on the performance of aqueous supercapacitors using carbide derived carbon (CDC) electrodes. The structures investigated by molecular simulations are compatible with the experimental results for CDC synthesized at 800°C, but not with the other two materials (CDC-1100 and YP-50F), which are more graphitic. In fact, the specific capacitance obtained for the latter two are in good agreement with molecular simulations of graphite electrodes, assuming that all the charge is localized in the first plane in contact with the electrode (a very good approximation). Our molecular simulations further allow to examine the solvation of ions inside the electrodes. Unlike what was observed for large organic ions dissolved in acetonitrile, we find that most Na+ cations remain fully solvated. Overall, microporous carbons such as CDCs are good candidates for applications involving aqueous supercapacitors, in particular the harvesting of blue energy or desalination, but their performance remains to be optimized by tailoring their microstructure.