Ceramic composite electrodes

Sonoelectrochemistry has also been used for the efficient employment of porous electrodes, such as carbon nanofiber-ceramic composites electrodes in the reduction of colloidal hydrous iron oxide [59], In this kind of systems, the electrode reactions proceed with slow rate or require several collisions between reactant and electrode surface. Mass transport to and into the porous electrode is enhanced and extremely fast at only modest ultrasound intensity. This same approach was checked in the hydrogen peroxide sonoelectrosynthesis using RVC three-dimensional electrodes [58]. 

Murphy MA, Marken F, Mocak J (2003) Sonoelectrochemistry of molecular and colloidal redox systems at carbon nanoHber-ceramic composite electrodes. Electrochim Acta 48 3411-3417... 

Amperometric detection has been widely used for sol-gel biosensing and many devices have been described (Lev, 1997 Wang, 1999 CoUinson, 2000 Przybyt, 2002). These methods are very convenient, but silica is not electronically conductive (Willner, 2000). Therefore carbon-ceramic composite electrodes (CCE) in which an enzyme-loaded carbon powder is mixed to the sol-gel solution have been developed (Gun, 1996 Sampath, 1996a Wang, 1997). 

Carbon-ceramic composite electrodes (CCEs) and the closely related metal-sihcate electrodes are comprised of carbon or metal dispersion in sol-gel derived silicates or Or-mocers. In this construction the silicate serves as a porous binder for the conductive dispersion. The conductive component is added as powders, nanoparticles, or nanotubes whose particle size ranges between sub-millimeter and a few nanometers. The initial intention was to provide improved conductivity by the interconnected conductive powder, but soon, other favorable attributes of the metal-sihcate hybrids were discovered, including improved catalytic reactivity, biological compatibility, and control of the thickness of the wetted section of the electrodes in aqueous electrolyte. Since the metal silicate and graphite silicate call for different preparation protocols they are addressed separately. 

Figure 16-8. Scheme of a 3-electrode fuel cell with details of the hydrophobic carbon ceramic composite electrode. The inserts show unwetted (left) and flooded (middle) sections of the CCE. The active section of a wetted channels electrode is shown in the right insert (after Rabinovich and Lev, 2001). 

Four different classes of composite ceramic electrodes were reported (1) ceramic carbon electrodes, (2) metal powder-ceramic composite electrodes, (3) carbon nanotube-silicate composites, and (4) coated aluminosilicate-ceramic electrodes. The first two fillers are basically three dimensional, whereas the third and fourth classes represent 1-D and 2-D anisotropic fillers. 

Metal Ceramic Composite Electrodes (Metal CCEs)... 

Wang, P, and G. Y. Zhu, 2002. Cupric hexacyanoferrate nanoparticle modified carbon ceramic composite electrodes. Chinese J Chem 20 374—80. 

Salami A, Hallaj T (2004) Adsorption and reactivity of chlorogenic acid at a hydrophobic carbon ceramic composite electrode application for the amperometric detection of hydrazine. Electroanalysis 16 1964—1971... 

Zhu, L., Tian, C, Zhai, J., and Yang, R. (2007) Sol-gel derived carbon nanotubes ceramic composite electrodes for electrochemical sensing. Sens. Actuators B, 125 (1), 254-261. 

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