Adsorption of Surface-Active Agents at Interfaces: The Electrical Double Layer

2004 ◽  
pp. 34-104 ◽  
Keyword(s):  
Double Layer ◽  
Electrical Double Layer ◽  
Surface Active Agents ◽  
Surface Active

The Penetrating Power of β-Decay Recoils of Epithermal Energies in Organic Matter

1971 ◽  
Vol 49 (22) ◽  
pp. 3692-3699 ◽  
Author(s):  
N. H. Shafrir
Keyword(s):  
Gas Phase ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Adsorption Layer ◽  
Unit Area ◽  
Initial Energy ◽  
Recoil Energy ◽  
Β Decay ◽  
Counter Ions ◽  
Surface Active

A method for the measurement of the extent of dislocation of the β-decaying nucleus from its equilibrium position is described. An ionized layer formed at the surface of an aqueous solution of an ionic surface-active substance served as a source of β-disintegrating atoms. The primary adsorbed surface-active ions give rise to an electrical double layer within the liquid phase. When the solution contains β-active ions, some will join the electrical double layer near the surface as counter ions. It was found that radioactive β-recoils arising in an adsorbed surface layer are able to leave the surface, collected on a negatively charged plate, and counted. In order to reach the gas phase, the β-recoils have to penetrate the primary organic adsorption layer. When the expanded adsorption layer is gradually compressed, particles of lower energy are stopped, resulting in decreased recoil activity. Extrapolation to zero β-recoil activity gives an approximate value for the mass per unit area of organic material which stops completely atoms of certain initial energy. For particle energies between 2 to 22 eV, a linear dependence is found between the maximum β-recoil energy and the "penetrating power". The corresponding organic stopping layers for this energy region are between 1.0 to about 1.6 × 10−7 g/cm2.

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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