Molecular Description of Electrolyte Solution in a Carbon Aerogel Electrode

Abstract

We develop a molecular theory of aqueous electrolyte solution sorbed in a nanoporous carbon aerogel electrode, based on the replica reference interaction site model (replica RISM) for realistic molecular quenched-annealed systems. We also briefly review applications of carbon aerogels for supercapacitor and electrochemical separation devices, as well as theoretical and computer modelling of disordered porous materials. The replica RISM integral equation theory yields the microscopic properties of the electrochemical double layer formed at the surface of carbon aerogel nanopores, with due account of chemical specificities of both sorbed electrolyte and carbon aerogel material. The theory allows for spatial disorder of aerogel pores in the range from micro-to macroscopic size scale. We considered ambient aqueous solution of 1 M sodium chloride sorbed in two model nanoporous carbon aerogels with carbon nanoparticles either arranged into branched chains or randomly distributed. The long-range correlations of the carbon aerogel nanostructure substantially affect the properties of the electrochemical double layer formed by the solution sorbed in nanopores.

Molecular Theory of Solvation and Electrical Double Layer in Nanoporous Carbon Electrodes

“…A generalization of RISM molecular theory of solvation to solutions sorbed in disordered nanoporous materials by using the replica method in statistical mechanics of quenched-annealed systems, the so-called replica RISM-KH-VM theory (18,19), provides full microscopic details of the solvation structure and thermodynamics and electrochemical properties averaged over the thermal motion of sorbed solution as well as over the quenched spatial distribution of nanopores with different shapes and sizes in the host nanoporous matrix, that is, morphology of nanoporous material (18)(19)(20)(21)(22)(23)(24)(25). This theory enables predictive molecular modeling of thermochemistry and electrochemistry of electrolyte solutions sorbed in functionalized nanoporous materials.…”

“…This theory enables predictive molecular modeling of thermochemistry and electrochemistry of electrolyte solutions sorbed in functionalized nanoporous materials. In particular, it reveals the mechanisms of sorption and supercapacitance in nanoporous carbon electrodes (21)(22)(23)(24)(25). The replica RISM-KH-VM theory predicts, from the first principles of statistical mechanics, such effects as phase transitions and solvent-specific wetting in nanoporous carbon materials (20), water depletion in hydrophobic carbon nanopores (20,(23)(24)(25), asymmetry in solvation and adsorption of cations and anions (18)(19)(20)(21)(22)(23)(24)(25), desalination of simple ions in hydrophobic nanopores and its reversal with external voltage applied (23)(24)(25), efficient removal of ionic impurities from an aqueous waste stream by a nanoporous carbon electrosorption cell (23), and specific adsorption at chemical functionalities on the surface of carbon nanopores (18,19).…”

Improvements of DRISM calculations: symmetry reduction and hybrid algorithms

“…It has been employed for investigations on monoatomic and molecular organic ions and neutral molecules, 34,35,[38][39][40][41][42][43][44][45] including biomolecules such as peptides and proteins. [46][47][48] Other fascinating extensions of the standard RISM approach include the PRISM theory, 49,50 specifically adopted for application to polymer melts and solutions, [51][52][53][54][55][56][57][58][59] the replica RISM theory [60][61][62][63][64][65][66] for molecular fluids sorbed in a matrix and the singlet RISM (SRISM) theory 67,68 for the calculation of wall/fluid site-density profiles at solid/liquid interfaces.…”

Iraq Reconstruction Project Terminations Represent a Range of Actions

“…Other groups have focused on improving the electrochemical properties of alternative forms of carbon such as carbon fibers (2,8,11), carbon nanotubes (1,14,17), and carbon foams (4,18,19). These carbon-based materials are particularly attractive owing to their continuous structure and inherent electrical conductivity, obviating the need for a polymer binder and metal substrate that add parasitic mass in granular carbon anodes.…”

“…Carbon nanofoams are a carbonized product of polymer aerogels combined with carbon fibers. They have demonstrated favorable anodic properties (4,18,19) and have been developed for commercial electrode use (24).…”