Ionization Difference between Weak and Strong Electrolytes as Perturbed by Conductivity Spectra Analysis

Abstract

While the static structure of aqueous electrolytes has been studied for decades, their dynamic microscopic structure remains unresolved yet critical in many areas. We report a comparative study of dc and ac (1 Hz to 20 GHz) conductivity data of weak and strong electrolytes, highlighting previously missing differences and similarities. Based on these results, we introduce into consideration the intrinsic short-lived ions of water, namely, excess protons (H3O+) and proton holes (OH–). We show that the model accounting for the neutralization of these ions by the species of electrolyte explains the conductivity of aqueous solutions in the concentration range 10–7–10 M. Based on independent experimental data, we hypothesize that the aggregation of the species in weak electrolytes may determine the main difference between the conductivity of weak and strong electrolytes. Our results push forward the understanding of the dynamic structure of aqueous electrolyte solutions and are important to nanofluidic, biological, and electrochemical systems.

Confinement-Controlled Water Engenders Unusually High Electrochemical Capacitance

“…In these pores, the electrical conductivity of pure water is comparable to that of strong electrolytes. 36 A further decrease of d down to the angstrom scale leads to a sharp decrease in all of the cell properties. This happens presumably as a result of the overlapping of the interfacial water layers of the opposite sides of the pore and the subsequent Coulomb blocking of the channel.…”

“…The maximum values of the conductivity σ ab and the capacitance C s , which are related to CE and the charge q , are observed for the grain size d max ≈ 10 nm or the pore size r max ≈ 3 nm (see below). In these pores, the electrical conductivity of pure water is comparable to that of strong electrolytes . A further decrease of d down to the angstrom scale leads to a sharp decrease in all of the cell properties.…”

“…In other words, any nanoconfined water can be treated as a superposition of bulk water and interfacial water, whose effective medium parameters depend upon their volume fractions. The size effect on the electrical conductivity of confined water is equivalent to increasing the frequency or adding electrolytes. , However, high conductivity and capacity are achieved without foreign species. This fact positively distinguishes our device from those of other electric energy accumulators.…”

“…The size effect on the electrical conductivity of confined water is equivalent to increasing the frequency 32 or adding electrolytes. 36 , 37 However, high conductivity and capacity are achieved without foreign species. This fact positively distinguishes our device from those of other electric energy accumulators.…”