Fuel PEM

As with batteries, differences in electrolytes create several types of fuel cells. The automobile s demanding requirements for compactness and fast start-up have led to the Proton Exchange Membrane (PEM) fuel cell being the preferred type. This fuel cell has an electrolyte made of a solid polymer. 

However, there are several issues with widespread methanol usage. Methanol production from natural gas is relatively inefficient ( 67%), and this largely offsets the vehicular improvement in efficiency and carbon dioxide reduction (since gasoline can be made with "85% efficiency from oil). Additionally, the PEM fuel cell demands very pure methanol, which is difficult to deliver using existing oil pipelines and may require a new fuel distribution infrastructure. 

Although it is attractive to directly convert chemical energy to electricity, PEM fuel cells face significant practical obstacles. Expensive heavy metals like platinum are typically used as catalysts to reduce energy barriers associated with the half-cell reactions. PEM fuel cells also cannot use practical hydrocarbon fuels like diesel without complicated preprocessing steps. Those significantly increase the complexity of the overall system. At this time, it appears likely that PEM fuel cells will be confined to niche applications where high cost and special fuel requirements are tolerable. 

The concept of a promoter can also be extended to the case of substances which enhance the performance of an electrocatalyst by accelerating the rate of an electrocatalytic reaction. This can be quite important for the performance, e.g., of low temperature (polymer electrolyte membrane, PEM) fuel cells where poisoning of the anodic Pt electrocatalyst (reaction 1.7) by trace amounts of strongly adsorbed CO poses a serious problem. Such a promoter which when added to the Pt electrocatalyst would accelerate the desired reaction (1.5 or 1.7) could be termed an electrocatalytic promoter, or electropromoter, but this concept will not be dealt with in the present book, where the term promoter will always be used for substances which enhance the performance of a catalyst. 

L. Ploense, M. Salazar, B. Gurau, and E. Smotkin, Spectroscopic study ofNEMCA promoted alkene isomerizations at PEM fuel cell Pd-Nafion cathodes, Solid State Ionics 136-137, 713-720(2000). 

Successful applications of the oxygen-modified CNFs are reported on immobilization of metal complexes ]95], incorporation of small Rh particles [96], supported Pt and Ru CNFs by adsorption and homogeneous deposition precipitation ]97, 98], Co CNFs for Fischer-Tropsch synthesis ]99], and Pt CNFs for PEM fuel cells [100]. 

Figure 8.31. Principle of a Polymer Electrolyte Membrane (PEM) fuel cell. A Nation membrane sandwiched between electrodes separates hydrogen and oxygen. Hydrogen is oxidized into protons and electrons at the anode on the left. Electrons flow through the outer circuit, while protons diffuse through the...

While the PEM fuel cells appear to be suitable for mobile applications, SOFC technology appears more applicable for stationary applications. The high operating temperature gives it flexibility towards the type of fuel used, which enables, for example, the use of methane. The heat thus generated can be used to produce additional electricity. Consequently, the efficiency of the SOFC is -60 %, compared with 45 % for PEMFC under optimal conditions. 

How does a fuel cell work What are SOFC and PEM fuel cells ... 

Why is the PEM fuel cell so sensitive to CO, while the SOFC cell is not ... 

Although ORR catalysts for DMFCs are mostly identical to those for the PEM fuel cell, one additional and serious drawback in the DMFC case is the methanol crossover from the anode to the cathode compartment of the membrane electrode assembly, giving rise to simultaneous methanol oxidation at the cathode. The... 

Susac D, Sode A, Zhu L, Wong PC, Teo M, Bizzotto D, Mitchell KAR, Parsons RR, Campbell SA (2006) A methodology for investigating new nonprecious metal catalysts for PEM fuel ceUs. J Phys Chem B 110 10762-10770... 

The second example describes distributed, mobile and portable power-generation systems for proton-exchange membrane (PEM) fuel cells [106]. A main application is fuel processing units for fuel cell-powered automobiles it is hoped that such processing units may be achieved with a volume of less than 8 1. 

Bi W, Gray GE, EuUer TE. 2007. PEM fuel cell Pt/C dissolution and deposition in nation electrol)te. Electrochem Solid State Lett 10 B101-B104. 

Darling RM, Meyers JP. 2005. Mathematical model of platinum movement in PEM fuel cells. J Electrochem Soc 152 A242-A247. 

Healy J, Hayden C, Xie T, Olson K, Waldo R, Brundage A, Gasteiger H, Abbott J. 2005. Aspects of the chemical degradation of PPSA ionomers used in PEM fuel cells. Fuel Cells 5 302-308. 

Yasuda K, Taniguchi A, Akita T, loroi T, Siroma Z. 2006b. Platinum dissolution and deposition in the polymer electrolyte membrane of a PEM fuel cell as studied by potential cycling. Phys Chem Chem Phys 8 746-752. 

Campbell S. 2006. Ballard Power System. Development of transition metal/chalcogen based cathode catalysts for PEM fuel cells. DOE Hydrogen Program Review, May 16-19, Washington, DC. Available at http //www.hydrogen.energy.gov/annual review06 fuelcells.html (click on catalysts section). 

Liu P, Nprskov JK. 2001a. Kinetics of the anode processes in PEM fuel cells— The promoting effect of Ru in PtRu anodes. Fuel Cells 1 192. 

Gasteiger HA, Panels JE, Yan SG. 2004. Dependence of PEM fuel cell performance on catalyst loading. J Power Sources 127 162-171. 

In this article we reveal the process we used to make a proton exchange membrane (PEM) fuel cell. 

Finally, the holder for the catalyzed PEM fuel cell with its gas supply piping, insulators, and wiring studs is shown. 

Some PEM fuel cell performance data were obtained using an electrical resistor to provide a variable load. Two digital multimeters and a shunt resistor were used to measure the voltage and current, so we could calculate the power produced. 

Hussain, M.M., I. Dincer and X. Li, A preliminary life cycle assessment of PEM fuel cell powered automobiles. Appl. Thermal Eng., 27,2294-2299, 2007. 

The Hydrogen Research Institute in Canada has developed and tested a stand-alone renewable energy system composed of a 10 kW wind turbine, a 1 kWpeak photovoltaic array, a 5 kW alkaline electrolyzer, and a 5 kW PEM fuel cell. The components of the system are electrically integrated on a 48 V DC bus [50]. 

In the "PURE" project on the Shetland Islands, the wind-hydrogen system is composed of two wind generators of 15 kW power each, a 15 kW advanced alkaline electrolyzer operating at 55 bars, a 16-cylinder stack of 44 Nm3 H2 capacity at the same pressure, and a 5 kW PEM fuel cell [54],... 

Increasing the utilization of hydrogen as an energy carrier in transportation and distributed power generation applications based on proton exchange membrane (PEM) fuel cells will create a demand for plants that produce high-purity hydrogen as the primary product. 

---