Thermochemistry and electrochemistry of liquids and solutions sorbed in nanoporous materials is drastically different from bulk systems and planar interfaces due to substantial distortion of charge distribution in nanoporous geometry, including functionalities on the surface of nanopores, coupled with steric effects of nanoporous confinement on electrolyte ions and solvent molecules. At present, molecular simulations of electrolyte solution with complex molecular solvent (such as water, methanol, acetonitrile, or ionic liquids) sorbed in nanoporous electrodes with realistic morphology is virtually unfeasible due to severe challenges with representative sampling, including (i) an interplay of electrostatic and steric forces on large-space and long-time scales, (ii) surface wetting/dewetting, solvent expulsion/condensation in the nanopores, and salination/desalination of sorbed solution depending on the electrode charge, (iii) a necessity to satisfy chemical and mechanical balance between the sorbed and bulk electrolyte solution. The statistical-mechanical, replica RISM-KH-VM molecular theory of solvation in disordered materials1-3,7 yields the microscopic solvation structure statistical-mechanically averaged over the distribution of nanopores and thermal motion of sorbed solution. It predicts solvent-specific wetting2 and water depletion in hydrophobic nanopores,4-6 asymmetry in solvation and adsorption of cations and anions,3-6 desalination in hydrophobic nanopores and its reversal with external voltage,3-6 and specific adsorption in functionalized nanopores.1,3 The method reveals the specific capacitance of nanoporous electrodes is determined by the chemical balance in the Nernst-Planck equation, including the potential drop across the Stern layer at the surface of nanopores and the Gouy-Chapman layer statistically averaged over the nanoporous material, the osmotic term due to a difference in the ionic concentration in the electrodes and bulk solution, and the chemical potentials of sorbed solvated ions statistically averaged over the nanoporous material.3-71 A.Kovalenko, F.Hirata, J.Chem.Phys.115 ,8620(2001).2 A.Kovalenko, F.Hirata, J.Theor.Comput.Chem.2 ,381(2002).3 A.Kovalenko, F.Hirata, Cond.Matt.Phys.4 ,643(2001).4 A.Tanimura, A.Kovalenko, F.Hirata, Chem.Phys.Lett.378 ,638(2003).5 A.Kovalenko, J.Comput.Theor.Nanosci.1 ,398(2004).6 A.Tanimura, A.Kovalenko, F.Hirata, Langmuir 23 ,1507(2007).7 A.Kovalenko, Pure Appl.Chem.85  ,159(2013).

Molecular theory of solvation and electrochemistry in nanoporous electrodes

246th National Meeting (2013)

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