Thermodynamics of nano-porous carbon materials as adsorbents and electrochemical double-layer capacitor electrodes—Implications from computer simulation studies—

Abstract

Thermodynamics in a nano-porous environment is different from that in the bulk. Adsorption of molecules in nano-porous carbon materials has been intensively studied and their characteristic features such as capillary condensation have been understood from the thermodynamic aspects. We extended the thermodynamic argument to the case where nano-porous carbon materials are used as electrochemical double-layer capacitor electrodes by performing Monte Carlo simulations in the constant-voltage grand-canonical ensemble. In this paper, we discuss the applications of nano-porous carbon materials both as adsorbents and as electrodes on the same thermodynamic basis in a unified manner. The characteristic features of nano-porous carbon materials such as the anomalous pore size dependence of capacitance, voltage-induced expansion of nano-porous carbon electrodes, phase transitions, and selective adsorption are understood in terms of the balance between the van der Waals or electrostatic interaction and the volume exclusion interaction inside them. [TANSO 2014 (No. 262), 67–75.]