Cathode construction

Research has been conducted on many metals including Fe, Co, Mn and Pb in order to find an adequate replacement for Pt. Cobalt and iron have attracted the most attention. These two metals are typically combined with tetramethoxyphenylporphyrin (TMPP) or phthalocyanine (Pc) to form metal macrocyclic complexes. Pyrolyzed FePc and CoTMPP complexes have proven the most effective transition metal-based materials. FePc supported on Ketjen black carbon generated a power density of 634 mW m compared to 593 mW produced by a Pt cathode in the same 

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This consists of a hollow cathode, constructed from the element to be analyzed or from an alloy containing the element. The anode is a tungsten wire or ring. 

Lithium—sulfur dioxide cells also use a liquid cathode construction. The SO2 is dissolved in an organic solvent such as PC or acetonitrile. Alternatively, SO2 is pressurized at several bars to use it in the liquid state. The cell reaction is similar to that depicted in Figure 18, with electronically insulating... 

As with other metals with a high hydrogen overpotential (e.g., In, Pb, Hg, Cd), tin shows a very good selectivity and, under suitable conditions, produces formate in very high yields. Thus, Li and Oloman [88] have investigated the development of a continuous reactor at atmospheric pressure with a cathode constructed from a copper net onto which tin had been electrodeposited. Experiments with this three-dimensional cathode on the influence of process variables on yields and selectivity towards formate provided promising results, such that the system was scaled-up and subsequently monitored initially in a small pilot plant [89],... 

The lithium sulfur dioxide and the lithium thionyl chloride systems are specialty batteries. Both have liquid cathode reactants where the electrolyte solvent is the cathode-active material. Both use polymer-bonded carbon cathode constructions. The Li-S02 is a military battery, and the Li-SOCl2 system is used to power automatic meter readers and for down-hole oil well logging. The lithium primary battery market is estimated to be about 1.5 billion in 2007. 

Mesoporous yttrium zirconium oxide or mesoporous cerium oxide anodes and a mesoporous lanthanum strontium manganate cathode constructed from nanocrystallites of these materials organized by a templating mesophase can be used in solid-oxide fuel cells. Mesoporous TiCU has a potential application in dye-sensitized solar cells. 

As mentioned previously, the vacuum-deposited diaphragm developed in 1928, coupled with the vertical finger anode-cathode construction, initiated the Hooker S series cell. The S type cell continued until 1966, when the single C-60 cell was introduced. In 1970, the H series cell was introduced, with metal anodes replacing the graphite anodes. A summary of the major innovations in Hooker diaphragm-cell design is presented in Table 2.1. 

The cathode construction is of considerable importance in this process. Cathodes were tested made of a steel (nikel) rod as well as a rod to the lower end of which a perforated steel disc of 30 mm in diameter was fastened (the disc surface was perpendicular to the rod axis and immersed in the layer of Ta205 powder on the container bottom. 

TABLE 11.2 List of Materials Used for Cathode Construction, Catalog Numbers, and Their Vendors. 

Zhang, F., Merrill, M.D., Tokash, J.C, Saito, T., Cheng, S., Hickner, M.A., and Logan, B.E. (2011) Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors. Journal of Power Sources,... 

The carbon cathode bottom blocks are the most important part of the cathode construction, and this statement is not an overestimation. A single crack that reaches the surface of the block at startup may cause shutdown of the cell within the first months of service. On the other hand, the expected service life of the cell is calculated on the basis of the bottom wear. That is why the quality of carbon cathode blocks is given special attention (Fig. 2.18). 

Yet it is necessary to remember that the expectations on energy savings could be fully realized with the implementation of a drained cathode construction. In a drained cathode, Al will flow to some vessel due to the slopes of the cathode the Al film will be very thin. This design really gives the ability to decrease energy consumption due to of the decrease in voltage drop. It has been reported that the wetted surface of a traditional reduction cell permitted a 1-2 % increase in the current efficiency and an improved cathode current distribution [111] (Fig. 2.61). 

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