Electrosorption-induced deformation of a porous electrode with non-convex pore geometry in electrolyte solutions: A theoretical study

Abstract

Porous carbon is well known as a good candidate for the development of electrochemical double-layer capacitors. Predominantly, many conventional carbons are microporous and often well described by the assumption of slit pore geometry. However, there is a class of carbons that is significantly different from the others, namely templated mesoporous carbons. In this work, we study electrosorption-induced deformation in CMK-3–like mesopores having non-convex geometry. Our mean-field approach is based on the modified Poisson-Boltzmann equation taking into account the excluded volume of the ions within the hard-sphere model. We assume that the deformation is caused by two effects: ion osmotic pressure and electrostatic interactions of the electric double layers on charged rods. We estimated the pore-load modulus of the CMK-3–like material and found an agreement with the previously obtained values by small-angle neutron scattering (SANS) data analysis. Additionally, we studied the differential capacitance in the non-convex pore geometry and found that the behavior of the differential capacitance profiles was similar to that of the profiles obtained for flat electric double layers: the crowding regime at rather high electric potentials and more pronounced profile asymmetry with increasing differences in the ionic sizes.