Fig. 2: Capacitance of nanoporous carbon supercapacitor and its origin.

a Configuration of MD simulation system with the porous carbon electrode and ionic liquid electrolyte ([EMIM][BF₄]). b Differential capacitance of experiments (black), atomic model (red) and nanoslit model (blue) for porous carbons. The nanoslit model uses the average pore size of the porous carbons. Dashed lines represent the PZC values. c Total ion number as a function of the electrode potential. The subfigure represents the rate of ion number change with the electrode potential. d Schematic of the Voronoi sphere method. Red dots represent in-pore Voronoi nodes; the pore size d is defined as the diameter of the Voronoi sphere (in dark grey) with the Voronoi node as the center. e Number of ions in different-sized pores at the PZC. Pore sizes are classified into ultramicropores ( < 0.7 nm) and large micropores ( > 0.7 nm). f, g Change of ion number in different-sized pores, compared to the PZC, for negative (f) and positive (g) electrodes. h–j Local electrode charge (LEC) of ions in different-sized pores at the PZC (h), under negative (i) and positive (j) polarizations. Error bars in b, c, e–j indicate one standard deviation of four independent simulations. Source data are provided as a Source Data file.