Heat electric double layer

The electrical double-layer structure at Au(l 11), Au(110), Au(100), and Au(210) faces and at a pc-Au electrode has been studied in 5 x 10 3 and 1 x 10-2 M LiC104 solutions in DMSO by cyclic voltammetry and impedance methods.477 The electrodes were cleaned by heating in a flame ... 

Boudart (26) suggests that the presence of the electrical double layer produced by the surface dipoles can account for the observed fall in the heat of adsorption and change in work function as the surface coverage is increased. Furthermore, assuming that the dipole interaction is negligible, as will be the case for small surface coverages, the heat of adsorption and work function changes should be related by the equation... 

The cause of the decrease of the heat of chemisorption is, therefore, the same as we discussed in the preceding sections. Boudart (338) elaborated the idea recently, and he proved that it can explain the order of magnitude of the experimental figures for the decrease. In his equations Boudart uses the conception of an electric double layer with homogeneously distributed charges. As, however, the decrease of the heat of chemisorption AQ is numerically smaller than the change in work function A[Pg.125]

Semiconductors such as Ti02, Fe203, CdS, and ZnS are known to be photochemical catalysts for a wide variety of reactions. When a photon with an energy of hv matches or exceeds the band gap energy, E, of the semiconductor, an electron, e, is promoted from the valence band, VB, into the conduction band, CB, leaving a hole, h+, behind. Electrons and holes either recombine and dissipate the input energy as heat, get trapped in metastable surface states, or react with electron donors and acceptors adsorbed on the surface or bound within the electrical double layer. 

The above picture of water/oxide interface does not obviously show the simultaneous, primary and secondary adsorption on non-dissociated water molecules. In their review, Etzler and Drost-Hausen wrote [89] Furthermore, as mentioned elsewhere in this paper (and other papers by the present author and associates), it is obvious that vicinal water is essentially unaffected by electrical double layers . Several properties of the vicinal water appear to be similar for various solid surfaces characterized by various point of zero charge (PZC) values (the paradoxical effect ). It is therefore to be expected that the contribution to the changes of the heat of immersion with changing pH, produced by the secondarily adsorbed vicinal water, is negligible. 

Structural features of disperse systems, in particular the existence of the electrical double layer (EDL), are responsible for a number of peculiar phenomena related to heat and mass transfer and electric current propagation in such systems. The description of electromagnetic radiation propagation is also included in this chapter. These features are utilized in numerous practical applications and underlie methods used to study disperse systems. These methods include particle size distribution analysis, studies of the surface structure and of near-surface layers, the structure of the EDL, etc. In the most general way the most transfer phenomena can be described by the laws of irreversible thermodynamics, which allow one to carry out a systematic investigation of different fluxes that originate as a result of the action of various generalized forces. 

Kuznetsov and Ulstrup initialized recently a discussion on the importance of conformational dynamics and electrical double layer effects on charge transport characteristics in single metal/redox-molecule/metal tunneling junctions [237,253]. Tao et al. explored the stabihty and break down of Au-thiol contacts, and addressed quantitatively local ionic and electron heating in single junctions composed of redox-inactive molecules [254]. 

In the future it will be very important to study the role played by the main scaling effects (i.e.,viscous dissipation, flow work, compressibility) and micro-effects (rarefaction, electric double-layer effects) on the convective heat transfer for single-phase flows in microchannels with the aim to explain that many experimental results published in the open literature can be justified by using correctly the conventional theory. 

Electrokinetic flow covers in principle the transport of liquids (electroosmosis) and samples (electrophoresis) in respraise to an electric field. Both motions are associated with the electric double layer that is formed spraitaneously at the solid-liquid interface in which there is a net charge density. Compared to the traditional pressure-driven flow, electrokinetic flow is more suited to miniaturization due to its nearly plug-like velocity profile and much lower flow resistance. However, Joule heating is a ubiquitous phenomenon in electrokinetic flow that will affect the transport of both liquids and samples via temperature-sensitive material properties. 

Regarding the future directions for theoretical research oti Joule heating in electrokinetic flow, it may be interesting and important to clarify the true expressimi of Joule heating within electrical double layer, to determine the appropriate thermal boundary condition at the outlet of... 

Induced-charge and second-kind electrokinetic phenomena arise due to electrohydrodynamic effects in the electric double layer, but the term nonlinear electrokinetic phenomena is also sometimes used more broadly to include any fluid or particle motion, which depends nonlinearly on an applied electric field, fit the classical effect of dielectrophoresis mentioned above, electrostatic stresses on a polarized dielectric particle in a dielectric liquid cause dielectro-phoretic motion of particles and cells along the gradient of the field intensity (oc VE ). In electrothermal effects, an electric field induces bulk temperature gradients by Joule heating, which in turn cause gradients in the permittivity and conductivity that couple to the field to drive nonlinear flows, e.g., via Maxwell stresses oc E Ve. In cases of flexible solids and emulsions, there can also be nonlinear electromechanical effects coupling the... 

In the following sections, the main deviations from classical theory for the calculation of heat transfer in microchaimels are discussed. This discussion includes axial heat conduction in the fluid, conjugate heat transfer, surface roughness, viscous dissipation, thermophysical property variations, electric double layers, entrance region and measurement accuracy. Whenever possible, the reader is referred to design criteria and Nu correlations when the different aspects have to be taken into account. 

Mala et al. [54] suggested that Nusselt numbers may be well overestimated if the effect of an electric double layer (EDL) at the fluid-solid interface in liquid flow is not considered. An E D L is formed when non-conducting channel materials are used. The layer modifies the velocity profile, which decreases the heat transfer. For channels sizes larger than 40 tm, the effect of the EDL can be neglected and therefore has no influence on the heat transfer [55]. 

In the phenomenological theory, the basis of the electrical double layer effect on the elementary act of an electrochemical reaction is the application of the Br0nsted relation which connects the activation energy, Ea, of the process to the heat of the reaction (or reaction free energy) ... 

Shiraishi S (2012) Heat-treatment and nitrogen-doping of activated carbons for high voltage operation of electric double layer capacitor. Key Eng Mat 497 80-86... 

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