Reference Electrodes with Salt Bridges Contained in Nanoporous Glass: An Underappreciated Source of Error

Mousavi, Maral P. S.; Bühlmann, Philippe

doi:10.1021/ac402170u

Cited by 42 publications

(80 citation statements)

References 35 publications

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“…The reference electrode was prepared as described previously. 27 Briefly, a glass tube equipped with a Vycor glass plug was filled with acetonitrile solution of 10.0 mM AgNO 3 and 100 mM NBu 4 ClO 4 , and an Ag wire was inserted into the tube. The reference electrode was kept in a solution of identical composition for at least 1 week prior to measurements.…”

Section: Methodsmentioning

confidence: 99%

Unbiased Quantification of the Electrochemical Stability Limits of Electrolytes and Ionic Liquids

Mousavi

Dittmer

Wilson

et al. 2015

J. Electrochem. Soc.

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The electrochemical window is the potential range in which an electrolyte/solvent system does not get reduced or oxidized. Usually, voltammograms are measured, and the potentials at which specific current densities are reached are identified as the electrochemical limits. We measured electrochemical limits of several electrolytes-including ionic liquids-and show that this approach has disadvantages that can be overcome by an alternate approach of defining electrochemical limits. The choice of the cutoff current density, J cut-off , is arbitrary and strongly affects the determined electrochemical windows, which are strongly influenced by electrolyte mass transport. Moreover, the J cut-off method does not provide an accurate estimate of the electrochemical window at electrodes with high surface areas, where the capacitive currents are large. We propose a method that requires no definition of J cut-off . This method minimizes electrolyte mass transport effects, gives realistic electrochemical stability limits at high surface area electrodes, and is less affected by experimental parameters such as the scan rate. The method is based on linear fits of the current-voltage curve at potentials below and above the onset of electrolyte decomposition. The potential at which the two linear fits intersect is defined as the electrolyte electrochemical limit. Electrolytes and solvents are essential for the proper function of a variety of electrochemical devices, such as batteries and supercapacitors. The voltage polarization in these devices can cause electrochemical degradation of the electrolyte and solvent, resulting in device malfunction. This can be avoided by constraining the working range of the device to the electrochemical window limited by the electrolyte and solvent, i.e., the potential range in which they are chemically stable and do not get reduced or oxidized.1,2 Due to their localized charges, the inherently ionic electrolytes often have a lower electrochemical stability than neutral solvent molecules, and therefore frequently limit the device working range.2 There has been extensive research on modifying the structure of electrolytes to improve their electrochemical stability, and thus expanding their working range. [3][4][5][6][7] The determination of the electrochemical window of electrolytes is not well defined. Generally a current-voltage polarization curve is measured, starting at a voltage at which the electrolyte is electrochemically stable, followed by increasing or decreasing the potential to observe the anodic or cathodic decompositions, respectively. The potential at which a specific current density, J, is reached is defined as the cathodic or anodic limit of the electrolyte. This approach has several disadvantages, as noted by several researchers.3-5 Firstly, since the choice of the cut-off current density is arbitrary, different standards have been applied in the literature. Cut-off current densities, J cut-off , in the range of 0.01 to 5.0 mA/cm 2 were reported, 3,7-20 resulting in electrochemical ...

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Section: Methodsmentioning

confidence: 99%

Unbiased Quantification of the Electrochemical Stability Limits of Electrolytes and Ionic Liquids

Mousavi

Dittmer

Wilson

et al. 2015

J. Electrochem. Soc.

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“…The Debye length is inversely proportional to the square root of the ionic strength of the electrolyte solution and is written as follows:

λ_{D} = \sqrt{\frac{ε_{r} k_{normalB} T}{2 I}}

where ε r is the relative permittivity of the electrolyte solution, k B is the Boltzmann constant, T is the absolute temperature of the electrolyte solution, and I is the ionic strength of the electrolyte solution. For PBS solution at pH 7.4, ε r =80 and I = 162.7 mMol . The Debye screening length is approximately 1 nm.…”

Section: Discussionmentioning

confidence: 99%

“…For PBS solution at pH 7.4, ε r =80 and I = 162.7 mMol. 42 The Debye screening length is approximately 1 nm. Since the ionic diameter of hydrated PO 4 3− in aqueous solution is only 0.678 nm, 43 the effective pore size for all the samples seen by PO 4 3− is still significantly larger than the size of hydrated PO 4 3− ions, and therefore, should not be able to prevent their diffusion into the nanopore network.…”

Section: Chemistry Of Hydroxyapatite Formed On Nanoporous 30c70s Samplesmentioning

confidence: 99%

Influence of nanoporosity on the nature of hydroxyapatite formed on bioactive calcium silicate model glass

et al. 2018

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For hard tissue regeneration, the bioactivity of a material is measured by its ability to induce the formation of hydroxyapatite (HA) under physiological conditions. It depends on the dissolution behavior of the glass, which itself is determined by the composition and structure of glass. The enhanced HA growth on nanoporous than on nonporous glass has been attributed by some to greater specific surface area (SSA), but to nanopore size distribution by others. To decouple the influence of nanopore size and SSA on HA formation, we have successfully fabricated homogeneous 30CaO-70SiO 2 (30C70S) model bioactive glass monoliths with different nanopore sizes, yet similar SSA via a combination of sol-gel, solvent exchange, and sintering processes. After incubation in PBS, HA, and Type-B carbonated HA (HA/B-CHA) form on nanoporous monoliths. The XPS, FTIR, and SEM analyses provide the first unambiguous demonstration of the influence of nanopore size alone on the formation pathway, growth rate, and microstructure of HA/CHA. Due to pore-size limited diffusion of PO 4 3− , two HA/CHA formation pathways are observed:HA/CHA surface deposition and/or HA/CHA incorporation into nanopores. HA/CHA growth rate on the surface of a nanoporous glass monolith is dominated by the pore-size limited transport of Ca 2+ ions dissolved from nanoporous glass substrates. Furthermore, with increasing nanopore size, HA/CHA microstructures evolve from needle-like, plate-like, to flower-like appearance.

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“…where E is the measured potential of the electrochemical cell, E o is the standard potential of the cell (including contributions from the reference electrode and the liquid junction to the sample), 32,33 R is the ideal gas constant, T is the temperature, z is the charge of the measured ion, F is Faraday's constant, aDS is the activity of DS, KDS/Cl is the selectivity coefficient for DS over Cl -, and aCl is the activity of chloride. All solutions used in this study contained 1.0 mM NaCl to control the ionic strength and activity of chloride.…”

Section: Ion-exchanger Electrode Response To Sodium 1-dodecyl Sulfatementioning

confidence: 99%

Indirect Potentiometric Determination of Polyquaternium Polymer Concentrations by Equilibrium Binding to 1-Dodecyl Sulfate

2019

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Polyquaternium polymers are polycationic polymers that are contained in many hair shampoos and conditioners and are also often added to water to remove organic and inorganic anions by floc formation. While polyquaternium analysis is not trivial, electroanalytical methods have been proposed for their detection using either irreversible emf responses or reversible potential-driven extraction into and out of polymeric sensing membranes. We present here an alternative technique for the determination of a representative polyquaternium polymer, poly(dimethylamine-co-epichlorohydrin) chloride, by equilibrium binding with a singly charged anionic surfactant, 1-dodecyl sulfate. Binding of an anionic surfactant to the polyquaternium polymer simplifies electrochemical detection as the concentration of unbound surfactant can be monitored using the equilibrium Nernstian emf response of ion-exchanger membranes. The latter can be used to determine the nature of the binding interaction and allows for the straightforward determination of polyquaternium polymer concentrations by titration. Fig. 1 Repeat unit structure of poly(dimethylamine-co-epichlorohydrin) chloride.

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Reference Electrodes with Salt Bridges Contained in Nanoporous Glass: An Underappreciated Source of Error

Cited by 42 publications

References 35 publications

Unbiased Quantification of the Electrochemical Stability Limits of Electrolytes and Ionic Liquids

Unbiased Quantification of the Electrochemical Stability Limits of Electrolytes and Ionic Liquids

Influence of nanoporosity on the nature of hydroxyapatite formed on bioactive calcium silicate model glass

Indirect Potentiometric Determination of Polyquaternium Polymer Concentrations by Equilibrium Binding to 1-Dodecyl Sulfate

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