Ion Solvation in Neat Solvents

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments

“…The effect of the solution anion on the electrochemical behavior of the VFc units was first examined via cyclic voltammetry experiments of P(VFc-co-X)-CNT in the presence of various inorganic monovalent electrolytes with differing ionic radii and Gibbs free energies of hydration, −Δ G hyd (Figure b and Table S2, Supporting Information). − Ferrocene (Fc) possesses a molecular sensing capability for negatively charged species as a result of the coupled oxidation and ion-pairing reaction processes that occur during its electrochemical oxidation, which lead to the formation of a neutral complex between ferrocenium, Fc + , and an anion, A – (eq ) − normalF normalc + normalA − → normalF normalc + normalA − + normale − In the base case of the vinylferrocene homopolymer composite, PVFc-CNT, the variation in its pseudocapacitance corresponded relatively well with the −Δ G hyd value of the electrolyte anion. In general, smaller anions are more hydrated and hydrophilic and experience difficulty approaching the neutral ferrocene units, resulting in both a lower extent of ferrocene oxidation as well as a loss of redox activity.…”

“…Although strontium electrochemically intercalates into NiHCF, its behavior in the presence of competing cesium and sodium cations may potentially vary. Specifically, the higher valence, lower ionic radius, and increased −Δ G hyd of strontium relative to cesium , may impact its extraction. The electrosorption process yielded removal amounts of 154 mg Re/g VFc, 48 mg Cr/g VFc, and 70 mg Cs/g NiHCF, which equated to molar adsorptions of 0.5 to 0.9 mmol of the element per g of the redox-active component (Figure b).…”

“…For comparison, the same electrochemical tests performed with the oxyanions but using PVFc in perchlorate electrolyte instead showed negligible differences in the redox potentials and pseudocapacitances compared with those of PVFc cycled in pure perchlorate solution (Figure 4b). Similar trends were also observed when the Gibbs free energy of hydration was used as a descriptor for the oxyanions (Table S5 and Figure S16, Supporting Information), 36 and indicate that the change in electrochemical behavior may depend on anion hydrophilicity rather than molecular geometry. The selectivities of the ferrocene co-polymers for perrhenate were further probed by measuring their redox potentials at different perrhenate concentrations.…”

A charge-neutral organic cage selectively binds strongly hydrated sulfate anions in water

“…Anion binding in water is challenging 1 due to the significant energetic cost from anion dehydration 2 and the high dielectric constant of water diminishing electrostatic interactions. 3 In tackling those challenges, naturally occurring transmembrane proteins such as sulfate binding proteins, 4 phosphate binding proteins 5 and ClC channels/transporters 6 supply multiple hydrogen bonding donors from polar amino acid residues to encapsulate anions within a hydrophobic protein microenvironment, leading to modest-to-strong anion binding affinities.…”

Electroactive Behavior of Adjustable Vinylferrocene Copolymers in Electrolyte Media

“…160 to 180 F/g VFc for these three electrolyte anions (Figure ). To investigate this further, a variety of electrolyte anions and cations were selected and characterized using their respective Gibbs free energies of hydration, −Δ G hyd (Table S3), , and subsequently used to generate different 0.5 M solutions for the electrochemical cycling of P­(VFc 0.11 - co -HEMA 0.89 )–CNT at 0.1 V/s. As anticipated, no distinct correlation was noted between the extent of hydration of the electrolyte cation and the P­(VFc 0.11 - co -HEMA 0.89 )–CNT electrode capacity due to the anion-mediated redox nature of VFc (Figure a).…”