The Modified Gouy-Chapman Theory: Comparisons between Electrical Double Layer Models of Clay Swelling

Langmuir ◽  
1994 ◽  
Vol 10 (7) ◽  
pp. 2125-2130 ◽  
Author(s):  
Jeffery A. Greathouse ◽  
Scott E. Feller ◽  
Donald A. McQuarrie
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Clay Swelling ◽  
Electrical Double Layer Models

Salinity dependence of complex conductivity of unconsolidated and consolidated materials: Comparisons with electrical double layer models

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. D185-D198 ◽  
Author(s):  
Andreas Weller ◽  
Lee Slater
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
High Salinity ◽  
Data Sets ◽  
Strongly Correlated ◽  
Sandstone Sample ◽  
Physical Description ◽  
Electrical Double Layer Models ◽  
Polarization Term ◽  
Predicted Values

We examined the dependence of imaginary conductivity ([Formula: see text]) on pore fluid conductivity ([Formula: see text]) for an extensive database of 67 samples acquired from twelve independent studies. We compared fitting of functions describing the salinity dependence of [Formula: see text] for two models of the electrical double layer (EDL) polarization, both of which predict asymptotic behavior of [Formula: see text] at high [Formula: see text]. We define these models as the diffuse layer polarization (DLP) and Stern layer polarization (SLP) models based on the physical description of the salinity dependence of the surface polarization. We also examined the database for evidence of a high salinity decrease in [Formula: see text] not predicted by either model. The dependence of [Formula: see text] on [Formula: see text] prior to the polarization plateau predicted by both models approximates a simple empirical power law with an average exponent of 0.34. The salinity dependence predicted by the DLP model adequately describes most data sets. A fitting parameter representing the high salinity [Formula: see text] asymptote is strongly correlated ([Formula: see text]) with pore normalized specific surface ([Formula: see text]). The SLP model describes well the observations when a recently proposed additive polarization term representing the contribution of the protons is included. In this case, the SLP model provides an excellent fit to the data sets, including a low salinity asymptote (in log-log conductivity space) seen in some samples. Predicted values of the fitting parameters of the SLP model generally are consistent with the values expected based on the theory; the fitting parameter describing the high salinity asymptote of the SLP model is also strongly correlated ([Formula: see text]) with [Formula: see text]. The SLP and DLP models neglect a high salinity decrease in the polarization that is observed in numerous data sets from independent studies. New data acquired on a sandstone sample demonstrate that this high salinity decrease is likely not attributable to the limited phase accuracy of earlier measurements.

Modeling the Electrical Double Layer to Understand the Reaction Environment in a CO2 Electrocatalytic System

2019 ◽  
Author(s):  
Divya Bohra ◽  
Jehanzeb Chaudhry ◽  
Thomas Burdyny ◽  
Evgeny Pidko ◽  
wilson smith
Keyword(s):  
Electric Field ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Surface Reaction ◽  
Catalyst Surface ◽  
Local Reaction ◽  
Reaction Diffusion ◽  
Alkali Metal Cations ◽  
Applied Potential ◽  
Critical Aspect

<p>The environment of a CO<sub>2</sub> electroreduction (CO<sub>2</sub>ER) catalyst is intimately coupled with the surface reaction energetics and is therefore a critical aspect of the overall system performance. The immediate reaction environment of the electrocatalyst constitutes the electrical double layer (EDL) which extends a few nanometers into the electrolyte and screens the surface charge density. In this study, we resolve the species concentrations and potential profiles in the EDL of a CO<sub>2</sub>ER system by self-consistently solving the migration, diffusion and reaction phenomena using the generalized modified Poisson-Nernst-Planck (GMPNP) equations which include the effect of volume exclusion due to the solvated size of solution species. We demonstrate that the concentration of solvated cations builds at the outer Helmholtz plane (OHP) with increasing applied potential until the steric limit is reached. The formation of the EDL is expected to have important consequences for the transport of the CO<sub>2</sub> molecule to the catalyst surface. The electric field in the EDL diminishes the pH in the first 5 nm from the OHP, with an accumulation of protons and a concomitant depletion of hydroxide ions. This is a considerable departure from the results obtained using reaction-diffusion models where migration is ignored. Finally, we use the GMPNP model to compare the nature of the EDL for different alkali metal cations to show the effect of solvated size and polarization of water on the resultant electric field. Our results establish the significance of the EDL and electrostatic forces in defining the local reaction environment of CO<sub>2</sub> electrocatalysts.</p>

Electrical Double Layer Formation on Glassy Carbon in Aqueous Solution

2021 ◽  
pp. 138416
Author(s):  
Sofia B. Davey ◽  
Amanda P. Cameron ◽  
Kenneth G. Latham ◽  
Scott W. Donne
Keyword(s):  
Aqueous Solution ◽  
Double Layer ◽  
Glassy Carbon ◽  
Electrical Double Layer ◽  
Layer Formation

Enzyme Immobilization Behavior on the Surface of Hydroxyapatite Capsules under Alkaline Condition

2018 ◽  
Vol 782 ◽  
pp. 21-26
Author(s):  
Takeshi Yabutsuka ◽  
Masaya Yamamoto ◽  
Shigeomi Takai ◽  
Takeshi Yao
Keyword(s):  
Enzyme Immobilization ◽  
Double Layer ◽  
Isoelectric Point ◽  
Electrical Double Layer ◽  
Alkaline Condition ◽  
Bicarbonate Buffer

We prepared hydroxyapatite (HA) capsules encapsulating maghemite particles. In order to evaluate enzyme immobilization behavior of the HA capsules under alkaline condition, we immobilized five kinds of enzymes with different isoelectric point in carbonate/bicarbonate buffer (CBB, pH 10.0). When the enzymes in CBB were moderately charged, immobilization efficiency on the HA capsules showed the highest value. It was suggested that immobilization efficiency was affected according to both pI of enzyme and pH of the surrounding solution and that enzyme immobilized on the HA capsules by not only electrical double layer interactions but also ion interaction and other interactions.

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