Phosphoric acid electrolyte fuel

The behavior of Pt and other alloy electrocatalyst crystallites used as the electrode materials for phosphoric acid electrolyte fuel-cells. 

In chapter 4, Stonehart (a major authority in the field of H2 fuelcell technology and its fundamental aspects) writes, with co-author Wheeler, on the topic of Phosphoric Acid Fuel-Cells (PAFCs) for Utilities Electrocatalyst Crystallite Design, Carbon Support, and Matrix Materials Challenges. This contribution reviews, in detail, recent information on the behavior of very small Pt and other alloy electrocatalyst crystallites used as the electrode materials for phosphoric acid electrolyte fuel-cells. 

In parallel with these development, work has been carried out on phosphoric acid electrolyte fuel cells which operate at 200 C and are able to burn hydrogen containing CO2 impurity, using air rather than pure oxygen as the oxidant. They find application as combined heat and power generation in 40 kW sizes, while much larger units (4.8 MW) have been installed in Manhattan and in Tokyo for peak load generation in the electricity supply system[4]. 

King, J.M., and H.R. Kunz. 2003. Phosphoric acid electrolyte fuel cells. In Handbook of fuel cells, ed. H.A. Gasteiger, A. Lamm, and W. Vielstich, 287-300, West Sussex John Wiley Sons Ltd. 

There are three types of medium- and high-temperature fuel cells that we shall be considering in this chapter. The phosphoric acid electrolyte fuel cell (PAFC) is the most well developed of the three. Many PAFC 200-kW CHP systems are installed at hospitals. 

Alkali carbonates (for molten carbonate (electrolyte) fuel cell (MCFC)) Phosphoric acid (phosphoric acid (electrolyte) fuel cell (PAFC))... 

PAFC Phosphoric acid (electrolyte) fuel cell... 

J. M. King, and H. R. Kunz, Phosphoric Acid Electrolyte Fuel Cells, in Handbook of Fuel Cells—Fundamentals, Technology and Applications, Vol. 1, W. Vielstich, A. Lamm, and H. A. Gasteiger, Eds., Wiley, 2003, pp. 287-300. 

Figure 19.18. Data of electrochemical fuel cells, (a) Processes in a fuel cell based on the reaction between hydrogen and oxygen, (b) Voltage-current characteristic of a hydrogen-air fuel cell operating at 125°C with phosphoric acid electrolyte [Adlharl, in Energy Technology Handbook (Considine, Ed.), 1977, p. 4.61). (c) Theoretical voltages of fuel cell reactions over a range of temperatures, (d) Major electrochemical systems for fuel cells (Adlharl, in Considine, loc. cit., 1977, p. 4.62).

Phosphoric acid fuel cell (PAFC)—Phosphoric acid electrolyte with platinum catalyst. It can use hydrocarbon fuel and is suited for stationary applications. It can generate both electricity and steam. As many as 200 units in sizes ranging from 200 kW to 1 mW are in operation. 

Acid Fuel Cells Phosphoric Acid Electrolyte - Fickett, A.P., Fuel Cell Electrolysis Where Have We Failed Proc. of the Symp. on Electrode Materials and Processes for Energy Conversion and Storage, J.D.E. McIntyre, S. Srinivasan and F. G. Will (Eds.), Vol. 77-6, 546-558. Electrochemical Society, Princeton, Mew Jersey, 1977. 

The phosphoric acid electrolyte of the acid fuel cell is far from optimum, particularly because of the low catalytic activity of platinum and other similar catalysts for 02 reduction in this electrolyte. A promising approach is to replace this electrolyte with new perfluorinated acids, which have high 02 solubility and do not adsorb on the catalyst surface. This should lead to much-improved performance of the air cathode. Work is in progress in several laboratories on the preparation of these new acids (e.g., perfluorinated sulfonic, phosphonic, and phosphinic acids) as a replacement for phosphoric acid. Reasonably high conductivity at high ratios of acid to water is also an important consideration. 

The installation for test of fuel cells of 4 types (with polymeric, molten carbonate, solid oxide, and phosphoric acid electrolytes) is created in Coal Energy Technology Institute of National Academy of Sciences and Ministry of Fuel and Power of Ukraine. 

For fuel-cell operation, most often technical hydrogen obtained by the conversion of primary fuels such as methanol or petroleum products is used, rather than pure hydrogen obtained by electrolysis. Technical hydrogen always contains carbon monoxide and a number of other impurities, even after an initial purification. In the first experiments conducted in the mid-1980s it was shown that traces of CO in hydrogen used for the operation of fuel cells with phosphoric acid electrolyte lead to a marked increase in the hydrogen electrodepolarization. 

Raising the temperature, the adsorption equilibrium between hydrogen and carbon monoxide, jointly adsorbing on platinum, shifts in favor of hydrogen adsorption. This raises the highest admissible threshold concentration of carbon monoxide. The effect could be seen in fuel cells with phosphoric acid electrolyte, which work at temperatures of about 180-200°C and admit carbon monoxide concentrations in hydrogen as high as 100 ppm, despite the fact that platinum catalysts are used. 

Phosphoric Acid Fuel Cells (PAFC) are operating in the range of 160-200 °C. The phosphoric acid electrolyte is soaked in a microporous matrix of corrosion resistant, non-conducting materials. At this high temperature, PAFC can tolerate a substantial... 

One of the frequently advertised advantages of the phosphoric acid imbibed polybenzimidazole systems is their zero water drag coefficient and their possibihty to operate with dry hydrogen and oxygen. However, a vast literature has been devoted to the study of the proton conduction and the effect of relative humidity on the conductivity of the PBl-phosphoric acid system. The promoting effect and the physicochemical interactions of water vapors with the polymer electrolyte and on the fuel cell performance have been explicitly shown for the PBl/PPy(50)coPSF 50/50 polymer blend imbibed with phosphoric acid under fuel cell conditions. ... 

Different catalysts are used for AFCs. For the hydrogen oxidation reaction, carbon-supported platinum and platinum-palladium catalysts (e.g., noble metal catalysts) are suitable. However, one of the advantages of the AFC compared with acid electrolyte fuel cells, including the phosphoric acid fuel cell (PAFC) and the... 

As is well known, and as discussed by Neyerlin and others, there is an increase in polarization losses with phosphoric acid-based fuel cells, in comparison to low-temperature PFSA-based fuel cells, and this effect is thought to be due to the presence of phosphoric acid and/or its anions that adsorb onto the surface of the catalyst [47]. Because of this, high-temperature stacks based upon phosphoric acid-doped polymer electrolyte membranes are larger in order to get the same power output. The overall question is whether the benefit in system simplification overcomes the need for larger stacks, so that there is an overall net system benefit. Reducing the effect of the adsorbed anion species would, of course, have significant benefit at the stack and system levels. 

Equation 18.6 holds for both planar electrodes and gas diffusion electrodes in phosphoric acid electrolytes as well as in phosphoric acid fuel cells. However, in PEMFCs, Igarashi et al. [7] suggested that the current ratio should be directly proportional to rather than (l- o) - Nonetheless, increasing CO... 

A phosphoric acid fuel cell (PAFC) consists of an anode and a cathode made of finely dispersed platinum catalyst on a carbon and silicon carbide structure that holds the liquid phosphoric acid electrolyte. Typically, PAFC systems have an operating temperature of around 200°C. When used for the co-generation of electricity and heat, PAFC cells... 

Andrew, M.R., McNicol, B.D., Short, R.T. Drury, J.S. Electrolytes for methanol-air fuel-cells. 1. The performance of methanol electro-oxidation catalysts in sulfuric acid and phosphoric acid electrolytes. J.Appl. Electrochem. 1 (1977), pp. 153-160. 

Phosphoric Acid (PAFC) This is the most commonly used type of fuel cell for stationary commercitd sites such as hospitals, hotels, and office buildings. The electrolyte is concentrated phosphoric acid. The fuel cell operates at about 200°C. It is highly efficient and can generate energy at up to 85% (40% as electricity and another 45% if the heat given off is also used). 

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