Triple-layer electrodes

In addition to bilayered electrodes with a functional layer and a support layer, electrodes have also been produced with multilayered or graded structures in which the composition, microstructure, or both are varied either continuously or in a series of steps across the electrode thickness to improve the cell performance compared to that of a single- or bilayered electrode. For example, triple-layer electrodes commonly utilize a functional layer with high surface area and small particle size, a second functional layer (e.g., reference [26]) or diffusion layer with high porosity and coarse structure, and a current collector layer with coarse porosity and only the electronically conductive phase (e.g., reference [27]) to improve the contact with the interconnect. 

Thus, according to these theories, all univalent (1 1) electrolytes should behave the same way. However, this is not what was observed experimentally. Solutions of different 1 1 electrolytes (e.g., NaCl, NaBr, Nal, KI) show species-specific behavior. In order to interpret this specific behavior, Grahame (5) proposed a new model of the interphase the triple-layer model. The basic idea in the interpretation of the ion-specific behavior is that anions, when attracted into the interphase, may become dehydrated and thus get closer to the electrode. Each anion undergoes this to a different extent. This difference in the degree of dehydration and the difference in the size of ions results in the specific behavior of the anions. Ions that are partially or fully dehydrated are in contact with the electrode. This contact adsorption of ions allows short-range forces (e.g., electric image forces) to act between the metal elec-... 

Here, 41 indicates the thin film transistors, 51 the substrate, 43 a dielectric layer, 49 polysilicon gates, 50 gate electrodes, 55 contact plugs, 56 bottom electrodes, 53 the planarization layer, 54 the mercury cadmium telluride layer and 57 the top electrode layer. The planarization layer is formed from silicon oxide, silicon nitride, silicon oxide nitride or from a polyimide. The planarization layer may be formed as a double or triple layer. 

Fig. 5.2 Device configuration and working principle of OLEDs. (a) a triple-layer device showing a hole-transporting layer (HTL), emissive layer (EML) and electron-transporting layer (ETL) sandwiched between two electrodes (b) a double-layer device. An energy diagram showing hopping transport of holes and electrons in (c) a triple-layer device and (d) a double-layer device. Light comes out upon radiative decay of excitons.

Fiq. 1. The triple layer model of the electrode-electrolyte interface (10). 

Usually, artificial muscle based on electrostrictive, piezoelectric, electrostatic, or ferroelectric materials have been manufactured as a film of the dry polymer, both sides coated with a thin metallic film required to apply the electric field. Electrokinetic artificial muscles [5,6] are constituted by films of polymeric gel (polymer, solvent, and salt) and two electrodes, located as close as possible to the material or coating both on sides, which are required to apply the electric field that drives the electroosmotic process. Any of the actuators described in this paragraph has a triple layer structure metal-electroactive polymer-metal (Figure 16.2). 

A fourth model proposed, the Grahame model (Grahame, 1951), which is referred to as the triple-layer model, takes into consideration that ions could be dehydrated in the direction of the electrode and specifically adsorbed on the electrode. Thus, an inner layer between the electrode surface and the Helmholtz layer further modifies the structure of the double layer. The locus of electrical centers of unhydrated ions strongly attached to the electrode is called inner Helmholtz plane (IHP). Figure 5.5... 

Various models have been proposed for the electric double layer at an electrode-electrolyte interface. Briefly explain the structure of the electric double layer starting from the Helmholtz model to the triple-layer model and then identify the key features of each model. 

Here Ci/a is the differential capacitance of the inner Helmholtz layer relative to the electrode (5Ee/5( — s)), C2/a the differential capacitance of the outer Helmholtz layer relative to the inner Helmholtz layer dY,o/d triple layer behaves Uke two capacitors connected in series. 

They are applicable to electrodes of any shape and size and are extensively employed in electroanalysis due to their high sensitivity, good definition of signals, and minimization of double layer and background currents. In these techniques, both the theoretical treatments and the interpretation of the experimental results are easier than those corresponding to the multipulse techniques treated in the following chapters. Four double potential pulse techniques are analyzed in this chapter Double Pulse Chronoamperometry (DPC), Reverse Pulse Voltammetry (RPV), Differential Double Pulse Voltammetry (DDPV), and a variant of this called Additive Differential Double Pulse Voltammetry (ADDPV). A brief introduction to two triple pulse techniques (Reverse Differential Pulse Voltammetry, RDPV, and Double Differential Triple Pulse Voltammetry, DDTPV) is also given in Sect. 4.6. 

Closely spaced band electrodes (pairs or triples), with each electrode within the diffusion layer of the other, can be used for studying reactions, in a manner analogous to ring-disk generation-collection and redox recycling experiments (131,132). Unlike with rotating ring-disk electrodes, the product of the reaction at the collector electrode can diffuse back across the narrow gap to the... 

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