Overcharging and charge reversal in the electrical double layer around the point of zero charge

2010 ◽  
Vol 132 (5) ◽  
pp. 054903 ◽  
Author(s):  
G. Iván Guerrero-García ◽  
Enrique González-Tovar ◽  
Martín Chávez-Páez ◽  
Marcelo Lozada-Cassou
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Point Of Zero Charge ◽  
Charge Reversal ◽  
Zero Charge

The Electrical Double Layer

2004 ◽  
Author(s):  
W. Ronald Fawcett
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Silver Chloride ◽  
Mercury Electrode ◽  
Ionic Concentration ◽  
Specific Adsorption ◽  
Point Of Zero Charge ◽  
Voltage Source ◽  
External Voltage ◽  
Silver Silver

In examining the properties of the metal | solution interface, two limiting types of behavior are found, namely, the ideal polarizable interface and the ideally nonpolarizable interface. In the former case, the interface behaves as a capacitor so that charge can be placed on the metal using an external voltage source. This leads to the establishment of an equal and opposite charge on the solution side. The total system in which charge is separated in space is called the electrical double layer and its properties are characterized by electrostatic equilibrium. An electrical double layer exists in general at any interface at which there is a change in dielectric properties. It has an important influence on the structure of the interface and on the kinetics of processes occurring there. The classical example of an ideally polarizable interface is a mercury electrode in an electrolyte solution which does not contain mercury ions, for example, aqueous KCl. The charge on the mercury surface is altered using an external voltage source placed between the polarizable electrode and non-polarizable electrode, for example, a silver | silver chloride electrode in contact with the same solution. Within well-defined limits, the charge can be changed in both the negative and positive directions. When the mercury electrode is positively charged, there is an excess of anions in the solution close to the electrode. The opposite situation occurs when the electrode is negatively charged. An important point of reference is the point of zero charge (PZC), which occurs when the charge on the electrode is exactly zero. The properties of the electrical double layer in solution depend on the nature of the electrolyte and its concentration. In many electrolytes, one or more of the constituent ions are specifically adsorbed at the interface. Specific adsorption implies that the local ionic concentration is determined not just by electrostatic forces but also by specific chemical forces. For example, the larger halide ions are chemisorbed on mercury due to the covalent nature of the interaction between a mercury atom and the anion. Specific adsorption can also result from the hydrophobic nature of an ion.

Charge reversal seen in electrical double layer interaction of surfaces immersed in 2:1 calcium electrolyte

1993 ◽  
Vol 99 (8) ◽  
pp. 6098-6113 ◽  
Author(s):  
P. Kékicheff ◽  
S. Marc̆elja ◽  
T. J. Senden ◽  
V. E. Shubin
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Charge Reversal ◽  
Layer Interaction

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>

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