Commercial Applications of Electrolytic Cells

What volume of oxygen gas (measured at STP) is produced by the oxidation of water at the anode in the electrolysis of copper(II) sulfate in Example 21-1  

We use the same approach as in Example 21-1. Here we relate the amount of charge passed to the number of moles, and hence the volume of O2 gas produced at STP. 

The equation for the oxidation of water and the equivalence between the number of coulombs and the volume of oxygen produced at STP are 

The number of coulombs passing through the cell is 7.50 X 10 C. For every 4(9.65 X 10 coulombs) passing through the cell, one mole of O2 (22.4 L at STP) is produced. 

Notice how little product is formed by what seems to be a lot of electricity. This suggests 

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Earaday s Law of Electrolysis 21-7 Commercial Applications of Electrolytic Cells... 

Counting Electrons Coulometry and Faraday s Law of Electrolysis 21-7 Commercial Applications of Electrolytic Cells Voltaic or Galvanic Cells 21-8 The Construction of Simple Voltaic Cells... 

Today, the term solid electrolyte or fast ionic conductor or, sometimes, superionic conductor is used to describe solid materials whose conductivity is wholly due to ionic displacement. Mixed conductors exhibit both ionic and electronic conductivity. Solid electrolytes range from hard, refractory materials, such as 8 mol% Y2C>3-stabilized Zr02(YSZ) or sodium fT-AbCb (NaAluOn), to soft proton-exchange polymeric membranes such as Du Pont s Nafion and include compounds that are stoichiometric (Agl), non-stoichiometric (sodium J3"-A12C>3) or doped (YSZ). The preparation, properties, and some applications of solid electrolytes have been discussed in a number of books2 5 and reviews.6,7 The main commercial application of solid electrolytes is in gas sensors.8,9 Another emerging application is in solid oxide fuel cells.4,5,1, n... 

It must be recognized that Fig. 11.1 is only a highly simplified representation of an electrolytic cell. Actual commercial practice usually employs a connected series of such cells constructed in a manner to meet the needs of each specific operation. Frequently, the vessel containing the electrolyte is made of metal and serves as one of the electrodes. Other modifications are shown in connection with commercial applications of electrolysis. 

T. A. Liederbach, A.M. Greenbeig, and V.H. Thomas. Commercial Application of Cathode Coatings in Electrolytic Chlorine Cells, Commercial Application of Cathode Coatings in Electrolytic Chlorine Cells, In M.O. Coulter (ed.). Modem Chlor-Alkali Technology, Ellis Horwood, Chichester, (1980), p. 145. 

Solid state electrolyte cells have been developed and tested also for high-power pttrposes, for instance, in all-electric vehicle applications. The invention of the sodiirm/p-alirmina/sirlfur battery by Ford Motor Co. intensified interest in the commercial applications of solid electrolytes. 

To allow commercial applications of sensors at various potential emission sites, the construction of these sensors from solid materials is desirable, so as to minimize the size of the sensors and simplify the manufacturing process. To date, a number of small CO2 gas sensors have been developed, and these may be categorized by their sensing mechanism, whether based on optical cells, resistance/capacitance of semiconductors, or electromotive force (EMF)/current measurements based on solid electrolytes. However, such sensors continue to exhibit deficits, including low selectivity, poor chemical and physical stability, or high cost, and these problems must be mitigated to improve their usefulness. 

There are five classes of fuel cells. Like batteries, they differ in the electrolyte, which can be either liquid (alkaline or acidic), polymer film, molten salt, or ceramic. As Table 1 shows, each type has specific advantages and disadvantages that make it suitable for different applications. Ultimately, however, the fuel cells that win the commercialization race will be those that are the most economical. 

Electrolyte loss occurring in long-term operation of MCFC is another problem to be solved for practical application of MCFC. For commercialization, the MCFC should show stable performance over 40,000 hours. Electrolyte loss in MCFC is caused by various factors, e.g., corrosion of components, creepage, reaction with cell components and direct evaporation. These... 

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable types of fuel cells. Moreover, the electrolyte membrane and other cell components can be manufactured very thin, allowing for high power production to be achieved within a small volume of space. Thus, the combination of small size and fast start-up makes PEMFCs an excellent candidate for use in mobile power applications, such as laptop computers, cell phones, and automobiles. 

One of the applications for hydrogen is for Polymer Electrolyte Membrane (PEM) fuel cells. As mentioned earlier, one application is a hydrogen fuelled hybrid fuel cell / ultra-capacitor transit bus program where significant energy efficiencies can be demonstrated. Another commercial application is for fuel cell powered forklifts and other such fleet applications that requires mobile electrical power with the additional environmental benefits this system provides. Other commercial applications being developed by Canadian industry is for remote back-up power such as the telecommunications industry and for portable fuel cell systems. 

Swiss Roll Cell This cell has been developed in Switzerland [89]. A commercial application is one oxidation step at a NiOOH anode in alkaline solution for the vitamin C production [22]. Mesh electrodes of stainless steel (cathode 1) and nickel (anode 3) are rolled up together with spacers of polypropylene mesh (2,4) on the central current feeder (5) and mounted in a cylinder (cells up to 1 m diameter, 200 m active area). The electrolyte streams axially through the cell. 

Numerous demonstrations in recent years have shown that the level of performance of present-day polymer electrolyte fuel cells can compete with current energy conversion technologies in power densities and energy efficiencies. However, for large-scale commercialization in automobile and portable applications, the merit function of fuel cell systems—namely, the ratio of power density to cost—must be improved by a factor of 10 or more. Clever engineering and empirical optimization of cells and stacks alone cannot achieve such ambitious performance and cost targets. 

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