Fuel cell mixed reactant

Priestnall, M., Kotzeva, V., Fish, D., and Nilsson, E. Compact Mixed Reactant Fuel Cells, Journal of Power Sources, 106,21 (2002). 

Priestnall MA, Kotzeva VP, Fish DJ, Nilsson EM (2002) Compact mixed-reactant fuel cells. J Power Sources 106 21-30... 

Papageorgopoulos DC, Liu F, Conrad O (2007) Reprint of A study ofRhxSy/C andRuSex/C as methanol-tolerant oxygen reduction catalysts for mixed-reactant fuel cell applications . Electrochim Acta 53 1037-1041... 

Advances in mixed-reactant fuel cells. Fuel Cells, 4, 436-447. 

Aziznia A, Bonakdarpour A, Gyenge EL, Oloman CW (2011) Electroreduction of nitrous oxide on platinum and palladium towards selective catalysts for methanol-nitrous oxide mixed-reactant fuel cells. Electrochim Acta 56 5238-5244... 

SOFCs have largely converged on standard configurations, such as tubular or planar, with the structural support provided by the electrolyte, the anode, the metallic intercormector, or an inert porous support material. Each of these concepts has its own combination of advantages and disadvantages. In this section, some unconventional SOFC configurations and devices are discussed, and their performance and potential applications are considered in comparison with the more conventional approaches. This will include microtubular fuel cells, mixed reactant fuel cells, micro-planar fuel cells, and dual proton-oxygen ion fuel cells. 

THE PRINCIPLE OF MIXED-REACTANT SUPPLY MIXED-REACTANT FUEL CELLS... 

Barton, S.C., Patterson, T., Wang, E., Fuller, T.F., and West, A.C. (2001) Mixed-reactant, strip-cell direct methanol fuel cells. Journal of Power Sources, 96 (2), 329-336. 

In solid electrolyte fuel cells, the challenge is to engineer a large number of catalyst sites into the interface that are electrically and ionically connected to the electrode and the electrolyte, respectively, and that is efficiently exposed to the reactant gases. In most successful solid electrolyte fuel cells, a high-performance interface requires the use of an electrode which, in the zone near the catalyst, has mixed conductivity (i.e. it conducts both electrons and ions). Otherwise, some part of the electrolyte has to be contained in the pores of electrode [1]. 

Polybasic carboxylic hydroxy and amino acid aided synthetic routes directed towards obtaining mixed inorganic materials, especially for battery and fuel cell applications, are overviewed. It has been shown that, in spite of enormous number of papers on the subject, significant efforts should be undertaken in order to understand the basic principles of these routes. Possible influence of the structure of reactants employed in the process (acids, poly hydroxy alcohols, metal salts) is put forward, and some directions of future work in the field are outlined. 

In an improved design, called an MCFC network, reactant streams are ducted such that they are fed and recycled among multiple MCFC stacks in series. Figure 9-19b illustrates how the reactant streams in a fuel cell network flow in series from stack to stack. By networking fuel cell stacks, increased efficiency, improved thermal balance, and higher total reactant utilizations can be achieved. Networking also allows reactant streams to be conditioned at different stages of utilization. Between stacks, heat can be removed, streams can be mixed, and additional streams can be injected. 

Numerous efforfs have been made to improve existing fhin-film catalysts in order to prepare a CL with low Pt loading and high Pt utilization without sacrificing electiode performance. In fhin-film CL fabrication, fhe most common method is to prepare catalyst ink by mixing the Pt/C agglomerates with a solubilized polymer electrolyte such as Nation ionomer and then to apply this ink on a porous support or membrane using various methods. In this case, the CL always contains some inactive catalyst sites not available for fuel cell reactions because the electrochemical reaction is located only at the interface between the polymer electrolyte and the Pt catalyst where there is reactant access. 

The stability of membranes against thermomechanical and chemical stresses is an important factor in determining both their short- and long-term performance. Transport and mechanical properties of membranes affect the fuel cell performance, while the lifetime of a fuel cell is mostly dependent on the thermomechanical and chemical stability of the membrane. Thermomechanical and chemical degradation of a membrane will result in a loss of conductivity, as well as mixing of anode and cathode reactant gases. 

An optimum relationship between the DL and the flow field channels is a key factor in the overall improvement of fhe fuel cell s performance at both high and low current densities. Currently, flow field designs are typically serpentine, interdigitated, or parallel [207,264]. The FF plate performs several functions If is a current collector, provides mechanical support for the electrodes, provides access channels for the reactants to their respective electrode surfaces and for the removal of producf water, and it prevents mixing of oxidant, fuel, and coolant fluids. 

Shukla, A.K., Jackson, C.L., Scott, K., Murgia, G. 2002. A solid-polymer electrolyte direct methanol fuel cell with a mixed reactant and air anode. J Power Sources 111 43-51. 

The first and the second law of thermodynamics allow the description of a reversible fuel cell, whereas in particular the second law of thermodynamics governs the reversibility of the transport processes. The fuel and the air are separated within the fuel cell as non-mixed gases consisting of the different components. The assumption of a reversible operating fuel cell presupposes that the chemical potentials of the fluids at the anode and the cathode are converted into electrical potentials at each specific gas composition. This implies that no diffusion occurs in the gaseous phases. The reactants deliver the total enthalpy J2 ni Hi to the fuel cell and the total enthalpy J2 ni Hj leaves the cell (Figure 2.1). 

Regardless of the specific type of fuel cell, gaseous fuels (usually hydrogen) and oxidants (usually ambient air) are continuously fed to the anode and the cathode, respectively. The gas streams of the reactants do not mix, since they are separated by the electrolyte. The electrochemical combustion of hydrogen, and the electrochemical reduction of oxygen, takes place at the surface of the electrodes, the porosities of which provide an extensive area for these reactions to be catalysed, as well as to facilitate the mass transport of the reactants/products to/from the electrolyte from/to the gas phase. 

The mixed fuel and oxidant fuel cell design is similar to the monolithic fuel cell configuration except that there is only one reactant flow channel for both the fuel and the oxidant (Fig. Two approaches to this fuel... 

The less active reactant is then free to diffuse to the other electrode and react. The advantage of these designs is simple design. The main disadvantages are poor kinetic performance of the electrodes in the first strategy and operating the fuel cell with a mixed potential for the second. ... 

Recently it was proposed that PEMLC electrocatalysts may also be prepared by water-in-oil microemulsions. These are optically transparent, isotropic, and thermodynamically stable dispersions of two nonmiscible liquids. The method of particle preparation consists of mixing two microemulsions carrying appropriate reactants (metal salt + reducing agent), to obtain the desired particles. The reaction takes place during the collision of water droplets, and the size of the particles is controlled by the size of the droplets. Readers are referred to the early work of Boutonnet et al. [149], the review paper of Capek [150] and refs. [128,151], and 152 for fuel cell apphcations. The carbonyl route has the ability to control the stoichiometry between bimetallic nanoparticles, but also the particle size. The reader is referred to review papers for more details [106,107]. Other methods, including sonochemical and radiation-chemical, have been used successfully for the preparation of fuel cell catalysts (see, e.g., review articles 100 and 153). 

Supported Materials. - The prime example of this, indeed perhaps the only example, stems from fuel-cell technology where metals such as Ag or Pt were mixed with or supported on graphite or carbon substrates. The case of the fuel cell is a special one in that the reactant is frequently in gaseous form and the electrode, whatever its material, must be of a form that optimum contact between gas and liquid is made at the catalyst surface. Fuel-cell... 

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