Low temperature fuel cell

Cooling strongly depends on fuel cell operating temperature and also depends on the fuel cell s external environment. For low temperature fuel cells, cooling imposes a significant energy debit because pumps need to force coolant out to a heat... 

Concerns about global climate change have motivated new interest in low-carbon or noncarbon fuels. Recent rapid progress and industrial interest in low-temperature fuel cells (which prefer hydrogen as a fuel) for transportation and power applications have also led to a reexamination of hydrogen as a fuel. 

This reaction is of great technological interest in the area of solid oxide fuel cells (SOFC) since it is catalyzed by the Ni surface of the Ni-stabilized Zr02 cermet used as the anode material in power-producing SOFC units.60,61 The ability of SOFC units to reform methane "internally", i.e. in the anode compartment, permits the direct use of methane or natural gas as the fuel, without a separate external reformer, and thus constitutes a significant advantage of SOFC in relation to low temperature fuel cells. 

Sol-gel techniques have been widely used to prepare ceramic or glass materials with controlled microstructures. Applications of the sol-gel method in fabrication of high-temperature fuel cells are steadily reported. Modification of electrodes, electrolytes or electrolyte/electrode interface of the fuel cell has been also performed to produce components with improved microstructures. Recently, the sol-gel method has expanded into inorganic-organic hybrid membranes for low-temperature fuel cells. This paper presents an overview concerning current applications of sol-gel techniques in fabrication of fuel cell components. 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

When surveying the central milestones in the development of electrocatalysis for low temperature fuel cells operating in acidic environments, the following, listed in chronological order, seem to be the most outstanding ... 

Varcoe JR, Slade RCT. 2005. Prospects for alkaline anion-exchange membranes in low temperature fuel cells. Fuel Cells 5 187-200. 

Hogarth MP, Ralph TR. 2002. Catalysis for low temperature fuel cells. Part III Challenges for the direct methanol fuel cell. Platinum Metals Rev 46 146-164. 

Christoffersen E, Liu P, Ruban A, Skriver UL, Nprskov JK. 2001. Anode materials for low temperature fuel cells—A density functional theory study. J Catal 199 123. 

Russell AE, Rose A. 2004. X-ray absorption spectroscopy of low temperature fuel cell catalysts. Chem Rev 104 4613-4635. 

In addition to their proven capacity to catalyze a highly efficient and rapid reduction of O2 under ambient conditions (e.g., cytochrome c oxidase, the enzyme that catalyzes the reduction of >90% of O2 consumed by a mammal, captures >80% of the free energy of ORR at a turnover frequency of >50 O2 molecules per second per site), metalloporphyrins are attractive candidates for Pt-free cathodes. Probably the major impetus for a search for Pt-free cathodic catalysts for low temperature fuel cells is... 

The prevalence of the heme in O2 metabolism and the discovery in the 1960s that metallophthalocyanines adsorbed on graphite catalyze four-electron reduction of O2 have prompted intense interest in metaUoporphyrins as molecular electrocatalysts for the ORR. The technological motivation behind this work is the desire for a Pt-ffee cathodic catalyst for low temperature fuel cells. To date, three types of metaUoporphyrins have attracted most attention (i) simple porphyrins that are accessible within one or two steps and are typically available commercially (ii) cofacial porphyrins in which two porphyrin macrocycles are confined in an approximately stacked (face-to-face) geometry and (iii) biomimetic catalysts, which are highly elaborate porphyrins designed to reproduce the stereoelectronic properties of the 02-reducing site of cytochrome oxidase. 

G. Sandstede, E.J. Cairns, V.S. Bagotsky and K. Wiesener, History of low temperature fuel cells, in Handbook of Fuel Cells — Fundamentals, Technology and Applications, W. Vielstich, H. A. Gasteiger and A. Lamm, Eds., Wiley, New York, 2003 pp. 173-174. 

Fuel Cells and Primary Fuel Processing for Low-Temperature Fuel Cells. ..204... 

Conventional Processes and Catalysts for Hydrogen Generation and Their Limitations in Low-Temperature Fuel Cells Technology... 

However, in developing new fuel processors for hydrogen production to feed low-temperature fuel cells, one should bear in mind the following limitations of the conventional processes [29] ... 

However, if the major source of hydrogen is reformed natural gas, the cost of generating electricity with a low-temperature fuel cell would be about 0.20 per kilowatt-hour. This is more than double the average price for electricity. It would also produce 50% more carbon dioxide emissions than the most efficient natural gas plants which are combined cycle natural gas turbines. Low-temperature fuel cells operating on natural gas are not as efficient at generating electricity. A stationary fuel cell system achieves high efficiency by cogeneration. 

Lin, Y., et ah, Platinum/carbon nanotube nanocomposite synthesized in supercritical fluid as electrocatalysts for low-temperature fuel cells. The Journal of Physical Chemistry B, 2005. 109(30) p. 14410-14415. 

E. Antolini, Formation of carbon-supported PtM alloys for low temperature fuel cells A review, Mater. Chem. Phys. 78, 563-573 (2003). 

In low-temperature fuel cells (PEFC, AFC, PAFC), protons or hydroxyl ions are the major charge carriers in the electrolyte, whereas in the high-temperature fuel cells, MCFC, ITSOFC, and TSOFC, carbonate ions and oxygen ions are the charge carriers, respectively. A detailed discussion of these different types of fuel cells is presented in Sections 3 through 8. Major differences between the various cells are shown in Table 1-1. 

The ideal performance of a fuel cell depends on the electrochemical reactions that occur with different fuels and oxygen as summarized in Table 2-1. Low-temperature fuel cells (PEFC, AFC, and PAFC) require noble metal electrocatalysts to achieve practical reaction rates at the anode and cathode, and H2 is the only acceptable fuel. With high-temperature fuel cells (MCFC, ITSOFC, and SOFC), the requirements for catalysis are relaxed, and the number of potential fuels expands. Carbon monoxide "poisons" a noble metal anode catalyst such as platinum (Pt) in low-temperature... 

Activation region and concentration region more representative of low-temperature fuel cells. 

Utilization (U) refers to the fraction of the total fuel or oxidant introduced into a fuel cell that reacts electrochemically. In low-temperature fuel cells, determining the fuel utilization is relatively straightforward when H2 is the fuel, because it is the only reactant involved in the electrochemical reaction, i.e. 

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