Reticulated foam electrode

Carbon—Graphite electrodes are often used, but they are less stable toward corrosion/phys-ical degradation than platinum. Graphite is available in many forms, including woven cloths, reticulated foam, and glassy (vitreous) carbon rods and plates. Organic products at different types of graphite anodes may differ considerably [60]. 

The major objective in other designs such as packed beds of particles, fibers, reticulated foams, bipolar trickel towers and fluidized bed electrodes has been the extension of the electrode area in the direction of current flow (the so-called three-dimensional electrodes ) thereby increasing the specific area and hence the space-time yield. 

Rather than using plate electrodes, a much higher surface area is obtained by using reticulated (foam) cathodes (Chapter 2, section 2.4.2). This principle is exploited in the patented RETEC cell which employs one of three types of cathode (1) Copper foam is standard for many applications (2) Nickel foam used for special applications and (3) Carbon foam, particularly for precious metals (this aids subsequent refining operations, and minimizes contamination by base metals). 

Three-dimensional electrode materials that fit well into parallel-plate [75,91, 92,93] reactors are (i) reticulated metals [75,91-93], (ii) metalized plastics (metalization of polyurethane foams) [94] and (iii) carbon [95]. 

A promising high surface area material for three-dimensional electrodes is reticulated carbon (RVC) or metal. This material has been used in the Retec cell, which is an undivided monopolar connected reactor utilising a bank of vertical foam cathodes (60 x 50 cm) with interspersed DSA anodes. It has been demonstrated [26], using a 0.4 m long cathode, that the concentration of Cu(II) (in sodium sulphate, pH = 2) can be reduced from 10 ppm to approximately 0.1 ppm in a single pass even in the presence of air saturated solutions. 

A variant of the enhanced reaction zone concept is to utilize as catalyst support various porous three-dimensional electrodes with thickness between 200 to 2,000 pm. Thus, the electric contact resistance between the individual layers is eliminated. The three-dimensional matrix (such as various graphite felts, reticulated vitreous carbon, metal mesh, felt, and foam) supporting uniformly dispersed electrocatalysts (nanoparticles or thin mesoporous coating) could assure an extended reaction zone for fuel (methanol, ethanol, and formie aeid) electrooxidation, providing an ionic conductor network is established to link the catalytically active sites and the proton exchange membrane. The patent by Wilkinson et al. also suggests such electrode configurations (e.g., carbon foam, expended metal and reticulated metal) but experimental results were not provided [303]. 

IVfore recent electrode materials include metal and carbon foams (reticulates), carbon granules, fibre and cloth, and a range of metal meshes. 

In 2009, Joey Jung developed a high surface area current collector for both positive and negative electrodes with amnlticonductive substrate. The current collectors were fabricated via deposited lead alloy on reticulated, multiconductive substrates. The substrate material can be carbon foam or polymer. Figure 1.38 shows a comparison of the multiconductive polymer-based current collector and the conventional grid. 

Material costs will be a large factor in the total reactor costs. Mainly anodic materials commonly used in MFC reactors, such as graphite foams, reticulated vitreous carbon, graphite, and others, are quite expensive. Simplified electrodes. 

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