Journal of Materials Research


Effect of diffuse layer and pore shapes in mesoporous carbon supercapacitors

Jingsong Huanga1, Rui Qiaoa2, Bobby G. Sumpter and Vincent Meuniera3 c1

a1 Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6367

a2 Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634-0921

a3 Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6367


In the spirit of the theoretical evolution from the Helmholtz model to the Gouy–Chapman–Stern model for electric double-layer capacitors, we explored the effect of a diffuse layer on the capacitance of mesoporous carbon supercapacitors by solving the Poisson–Boltzmann (PB) equation in mesopores of diameters from 2 to 20 nm. To evaluate the effect of pore shape, both slit and cylindrical pores were considered. We found that the diffuse layer does not affect the capacitance significantly. For slit pores, the area-normalized capacitance is nearly independent of pore size, which is not experimentally observed for template carbons. In comparison, for cylindrical pores, PB simulations produce a trend of slightly increasing area-normalized capacitance with pore size, similar to that depicted by the electric double-cylinder capacitor model proposed earlier. These results indicate that it is appropriate to approximate the pore shape of mesoporous carbons as being cylindrical and the electric double-cylinder capacitor model should be used for mesoporous carbons as a replacement of the traditional Helmholtz model.

(Received December 14 2009)

(Accepted April 23 2010)

Key Words:

  • Energy storage;
  • Simulation