Graphite brush electrodes

Figure 4.4 Internal resistance obtained from Nyquist plots using impedance spectra of two MFCs with either a carbon cloth or graphite brush electrode. Rm is obtained as the value of the x-intercept. [Reprinted from Logan et al. (2007), with permission from the American Chemical Society.]...

Configuring the electrodes in the MFC. The MFC electrodes currently thought to be the most suitable for scale up consist of high specific surface area graphite brush electrodes and tubular cathodes. These electrodes could be placed in sequence (/.e., anodes then cathodes) or randomly in the same tank (Fig 9.4). Groups of anodes and cathodes would form a single anode-cathode module, with many electrodes placed in a single tank or module. The brushes and tubes within the module would need to be in close proximity to each other to minimize the distance for proton transfer and thus... 

Graphite brushes Surface area porosity Electrode spacing 1430/- Logan et al. (2007)... 

Structure and active material of the electrodes determine the overall power output of an SMFC to a great extent. Power densities reported for SMFCs are usually normalised to the anode surface area, since the fuel cell volumes are undetectable in most cases. The first SMFC which was built with Ft anode and Ft cathode provided a power density of 15 mW m [125]. SMFCs built with graphite disks electrodes generally produced a maximum power density of 18-32 mW m-2, depending on the geochemical characteristics of the site [42]. Other electrode materials include carbon cloth, stainless steel and carbon fibre brush. 

In the USA artificial graphite is now made on a scale exceeding 300 kilotonnes pa (1989), and is used mainly for electrodes, crucibles and vessels, and various unmachined shapes specialist uses include motor brushes and contacts and refractories of various sorts. 

Graphite electrodes are used in the electric arc production of steel, whereby 3 to 5 kg of electrode material is consumed to produce 11 of steel. A further wide field of application for graphite is the electrical industry, where carbon/graphite is used e.g as material for brushes. Graphite is also used to manufacture apparatus (e.g. heat exchangers) and, most recently, for heating elements to manufacture pure silicon for the production of wafers. 

Patel, A.K. Sharma, P.S. Prasad, B.B. (2009). Electrochemical sensor for uric acid based on a molecularly imprinted polymer brush grafted to tetraethoxysilane derived sol-gel thin film graphite electrode. Materials Science and Engineering C, 29,1545-1553. 

Vertically layered streaming, T shape, channel length = 48 mm, channel width = 3.3 mm, Pt/Ru and Pt nanoparticles in Naflon-based ink solution brushed on carbon paper as electrodes, graphite plates as current collectors, implementing of nano-porous separator at the fuel-electrolyte interfece, running at 80 °C with O2 supply of 50 seem, hot-pressed thin film of Nation over cathode to alleviate fuel crossover effects... 

Applications for graphite are many, varied, and include lubricants, pencils, battery electrodes, friction materials (e.g., brake shoes), heating elements for electric furnaces, welding electrodes, metallurgical crucibles, high-temperature refractories and insulations, rocket nozzles, chemical reactor vessels, electrical contacts (e.g., brushes), and air purification devices. 

Ferrocene units were tethered to electrodes by telechelic poly(ethylene oxide) [579] and showed preferential adsorption of pyrene end groups to highly oriented pyrolytic graphite [580]. Ferrocene-based polymer brushes were grafted from conducting surfaces, which imparted special electrochemical behavior [581-584] e.g., the interaction of these surfaces with cyclodextrin could be modulated by electrochemical means (Fig. 51) [583, 585]. 

Almost pure carbon or artificial graphite, which is suitable for carbon electrodes, motor brushes, dry cells, etc., can be made by calcining petroleum coke. In this process, the refinery coke is passed through a 100- to 125-ft cylindrical rotating kiln by which it is heated to a bright red heat. 

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