Electrode thermal diffusion properties

The Working Electrode Preparation and Thermal Diffusion Properties 148 Preparation of Self-Assembled Monolayers 150... 

Arrhenius plots of conductivity for the four components of the elementary cell are shown in Fig. 34. They indicate that electrolyte and interconnection materials are responsible of the main part of ohmic losses. Furthermore, both must be gas tight. Therefore, it is necessary to use them as thin and dense layers with a minimum of microcracks. It has to be said that in the literature not much attention has been paid to electrode overpotentials in evaluating polarization losses. These parameters greatly depend on composition, porosity and current density. Their study must be developed in parallel with the physical properties such as electrical conductivity, thermal expansion coefficient, density, atomic diffusion, etc. 

High quality IR spectra of different carbon surfaces were obtained by photo-thermal beam deflection spectroscopy (IR-PBDS) [123,124]. This technique was developed with the intention of providing an IR technique that could be used to study the surface properties of materials that are difficult or impossible to examine by conventional means. Recently, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) has been successfully applied to study the effect of different pretreatments on the surface functional groups of carbon materials [101,125-128]. Several studies aiming to improve the characterization of the carbon electrode surface and the electrode-electrolyte interface have been carried out using various in situ IR techniques [14,128-132]. The development of in situ spec-troelectrochemical methods has made it possible to detect changes in the surface oxides in electrolyte solutions during electrochemical actions. 

There are two kinds of polymer material that used in quasi-solid/solid state DSSCs. For quasi-solid electrolytes, polyionic liquids have been proposed as solvent and redox couple as solute. They appear in molten salts and present many promising properties, such as, high chemical and thermal stability and high ionic conductivity Their main drawback is related to its high viscosity, which makes the ions diffusion rather slow. As the transport of ions to the counter electrode in an ionic liquid matrix represents a rate-limiting step in DSSC (Bella, 2015), the performance of quasi-solid electrolytes based solar cell is imsatisfled. 

The porous cathode is generally made of Sr- and/or Co-doped LaMnOa perovskite mixed conductors. The LaCoOa (Sr-doped) material exhibits a high oxygen diffusivity and is therefore very attractive from an electrochemical point of view, but unfortunately suffers from an unacceptably high reactivity with zirconia and high coefficient of thermal expansion. The LaMnOa electrode (doped with Sr) on the other hand, is predominantly an electronic conductor. Various compositions are being considered to optimise the required properties. 

The diffuse layer is the region between the bulk and the Outer Helmholtz Plane (OHP) which is recognised as the plane of closest approach of non-specifi-cally adsorbed species. The properties of this layer can be explained in terms of an equilibrium between thermal motion and the long range coulombic interaction of the ions with the charge on the electrode. It can be regarded as the ionic atmosphere of the metal electrode, and is independent of the chemical nature of the ion. 

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