Electrochemistry, electrochemical surface area effect

Thus, in the metal/YSZ systems of solid-state electrochemistry, AC-impedance spectroscopy provides concrete evidence for the formation of an effective electrochemical double layer over the entire gas-exposed electrode surface. The capacitance of this metal/gas double layer is of the order of 100-500 pF cm-2 of superficial electrode surface area and of the order 2-10 pF cm-2 when the electrode roughness is taken into account and, thus, the true metal/gas interface surface area is used, comparable to that corresponding to the metal/solid electrolyte double layer. Furthermore AC-impedance spectroscopy... 

The field of chemistry concerned with the interrelation of electrical and chemical effects, especially the study of chemical changes caused by an electric current and the electrical energy production by chemical reactions, is termed electrochemistry [5]. While electrochemistry encompasses a huge array of different phenomena applied in a variety of technologies, applications, and characterization techniques, such as the surface area measurement by hydrogen adsorption discussed in Sect. 4.3.8, the main emphasis here will be focused on electrodeposition and devices based on electrochemistry, such as electrochemical supercapacitors and electrochromic displays. 

Most of the electrochemical phenomena occur in size regimes that are very small. The effects of size on diffusion kinetics, electrical double layer at the interface, elementary act of charge transfer and phase formation have recently been reviewed by Petrri and Tsirlina [12]. Mulvaney has given an excellent account of the double layers, optical and electrochemical properties associated with metal colloids [11]. Special emphasis has been given to the stability and charge transfer phenomenon in metal colloid systems. Willner has reviewed the area of nanoparticle-based functionalization of surfaces and their applications [6-8]. This chapter is devoted to electrochemistry with nanoparticles. One of the essential requirements for electrochemical studies is that the material should exhibit good conductivity. 

This novel effect has been termed non-Faradaic electrochemical modification of catalytic activity (NEMCA effect [5-15]) or electrochemical promotion [16] or in situ controlled promotion [20]. Its importance in catalysis and electrochemistry has been discussed by Haber [18], Pritchard [16] and Bockris [17], respectively. In addition to the group which first reported this new phenomenon [5-7], the groups of Lambert [12], Haller [10], Sobyanin [8], Comninellis [13], Pacchioni [21] and Stoukides [11] have also made important contributions in this area, which has been reviewed recently [14,15]. In this review the main phenomenological features of NEMCA for oxidation reactions are briefly surveyed and the origin of the effect is discussed in the light of recent kinetic, surface spectroscopic and quantum mechanical investigations. 

As mentioned earlier, thin films can be considered 2-D nanostructures. In the recent past, thin film-based technologies have been responsible for the design of an enormous variety of thin film-based electrochemical devices. 2-D nanostructures [91] composed of 0-D or 1-D materials are those that are associated with the interfacial properties of electrodes. In electrochemistry they are known as porous electrodes, and they sometimes possess an effective surface more than 1,000 times greater than the geometric area expected for a compact and homogeneous 2-D structured electrode, e.g., porous thin film-related electrodes [92-96]. 

An aim of this volume is to highlight rapidly developing areas of electroanalyt-ical chemistry and electrochemistry. In this context, the application of ultrasound on electrochemical processes is a topic of particular interest. In a series of three chapters, Compton and coworkers provide a treatment of the underlying physical aspects connected with the coupling of ultrasound to electrochemical systems (Chapter 2.8) and applications in electroanalysis (Chapter 2.9). The first of these chapters considers the effect of ultrasound on mass transport, on the electrode surface and on chemical reactions in solution, while the second chapter looks at the use of sonoelectrochemical methods in... 

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