Fuel cells cell catalysts

Paradoxically, all these significant recent contributions to the theory of the ORR, together with most recent experimental efforts to characterize the ORR at a fuel cell cathode catalyst, have not led at aU to a consensus on either the mechanism of the ORR at Pt catalysts in acid electrolytes or even on how to properly determine this mechanism with available experimental tools. To elucidate the present mismatch of central pieces in the ORR puzzle, one can start from the identification of the slow step in the ORR sequence. With the 02-to-HOOads-to-HOads route appearing from recent DFT calculations to be the likely mechanism for the ORR at a Pt metal catalyst surface in acid electrolyte, the first electron and proton transfer to dioxygen, according to the reaction... 

Jasinski R. 1964. A new fuel cell cathode catalyst. Nature 201 1212. 

Gary Jacobs and Burt Davis (University of Kentucky) review catalysts used for low-temperature water gas shift, one of the key steps in fuel processors designed to convert liquid fuels into hydrogen-rich gas streams for fuel cells. These catalysts must closely approach the favorable equilibrium associated with low temperatures, but be active enough to minimize reactor volume. The authors discuss both heterogeneous and homogeneous catalysts for this reaction, with the latter including bases and metal carbonyls. 

Alternative cathode catalysts to platinum have been the focus of many researchers over the past four decades. Numerous reviews have been published on various aspects and types of PEM fuel cell cathode catalysts.2,7-21 In this work we review the major classes of non-noble metal ORR catalysts in acidic electrolytes. The techniques used to study the catalysts, a brief history of catalyst development including major breakthroughs, and possible future directions will be discussed. 

Steigerwalt, S.E. et al., A Pt-Ru/graphitic carbon nanofiber nanocomposite exhibiting high relative performance as a direct-methanol fuel cell anode catalyst, J. Phys. Chem. B., 105, 8097, 2001. 

R. X. Liu, and E. S. Smotkin, Array membrane electrode assemblies for high throughput screening of direct methanol fuel cell anode catalysts, J. Electroanal. Chem. 535, 49-55 (2002). 

Wang, G., Mukherjee, P P, and Wang, C. Y. Optimization of polymer electrolyte fuel cell cathode catalyst layers via direct numerical simulation modeling. Electrochimica Acta 2007 52 6367-6377. 

Preparation of the Working Electrodes for Catalyst/Catalyst Layer Studies In fuel cell catalyst/catalyst layer down-selection, the process of preparing the working electrodes includes several steps ... 

Zhang J, Wang H, Wilkinson DP, Song D, Shen J, Liu ZS (2005) Model for the contamination of fuel cell anode catalyst in the presence of fuel stream impurities. J Power Sources 147 58-71... 

It is important to consider pH, temperature, and pressure since conventional fuel cells use catalysts that function at very low pH and high temperatures. 

Adcock, P.A. et al.. Transition metal oxides as reconfigured fuel cell anode catalysts for improved CO tolerance polarization data, J. Electrochem. Soc., 152, A459, 2005. 

Strasser, P. et al.. High throughput experimental and theoretical predictive screening of materials a comparative study of search strategies for new fuel cell anode catalysts, J. Phys. Chem. B, 107, 11013, 2003. 

Determination of Reaction Mechanisms Occurring at Fuel Cell Electro catalysts Using Electrochemical Methods, Spectroelectrochemical Measurements and Analytical Techniques... 

Van der Klink and Tong cover NMR studies of heterogeneous and electrochemical catalysts, and X-ray absorption spectroscopy studies are the focus of the chapter by Mukerjee. In Chapter 15, Stimming and Collins discuss STM and infrared spectroscopy in studies of fuel cell model catalyst. 

STM and Infrared Spectroscopy in Studies of Fuel Cell Model Catalysts Particle Structure and Reactivity... 

What, if any, relevance do such results have when predicting the influence of adsorbed bismuth on the CO of supported platinum nanoparticle catalysts In order to test the transferrability of results obtained on single crystals to practical fuel-cell anode catalysts, a series of experiments was performed [77] on a gas diffusion electrode of carbon-supported platinum (0.22 mg cm ) catalyst (Johnson Matthey). Figure 10 shows the results of polarization measurements for hydrogen oxidation at clean and bismuth-modified (0.65-ML) catalysts. In order to establish the CO tolerance of the electrodes, in addition to experiments involving pure H2,... 

Model electrodes with a dehned mesoscopic structure can be generated by a variety of means, e.g., electrodeposition, adsorption from colloidal solutions, and vapor deposition and on a variety of substrates. Such electrodes have relatively well-dehned physico-chemical properties that differ signihcantly from those of the bulk phase. The present work analyzes the application of in-situ STM (scanning tunneling microscopy) and ETIR (Eourier Transformed infrared) spectroscopy in determining the mesoscopic structural properties of these electrodes and the potential effect of these properties on the reactivity of the fuel cell model catalysts. Special attention is paid to the structure and catalytic behavior of supported metal clusters, which are seen as model systems for technical electrocatalysts. 

FTIR spectroscopy has been shown to be a useful tool in the characterization of fuel cell model catalysts. It has helped elucidate much information on the electronic and geometrical structure of surfaces, which may help in the explanation of unusual size effects on electrocatalysis. Surface diffusion of the adsorbed molecules has been seen from time- and potential-dependent IR spectroscopy showing that the oxidation of CO on Pt sites and Ru sites are coupled. There is... 

Use Alloys (low-alloy steels, stainless steel, copper and brass, permanent magnets, electrical resistance alloys), electroplated protective coatings, electro-formed coatings, alkaline storage battery, fuel cell electrodes, catalyst for methanation of fuel gases and hydrogenation of vegetable oils. 

Figure 10.1 Schematic drawing of a proton-exchange membrane fuel cell. CL = catalyst layer GDL = gas diffusion layer.

Recently, taking advantage of the very narrow size distribution of the metal particles obtained, microemulsion has been used to prepare electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) Catalysts containing 40 % Pt Ru (1 1) and 40% Pt Pd (1 1) on charcoal were prepared by mixing aqueous solutions of chloroplatinic acid, ruthenium chloride and palladium chloride with Berol 050 as surfactant in iso-octane. Reduction of the metal salts was complete after addition of hydrazine. In order to support the particles, the microemulsion was destabilised with tetrahydrofurane in the presence of charcoal. Both isolated particles in the range of 2-5 nm and aggregates of about 20 nm were detected by transmission electron microscopy. The electrochemical performance of membrane electrode assemblies, MEAs, prepared using this catalyst was comparable to that of the MEAs prepared with a commercial catalyst. 

Recently great interest has been shown all over the world in the study of desulfurization of liquid fuels on various adsorbents [7, 8, 13, 145-158], It is driven by the fact that US federal regulations mandate the reduction in sulfur level for gasoline and diesel fuel to 30 and 15 ppm, respectively. The current levels are 300-500 ppmw. The new requirements will be implemented in 2006 [6]. Tire reason for lowering sulfur level, besides detrimental environmental effects is in the fact that sulfur compounds poison both automobile and fuel cell reformer catalysts. 

For Several years the Laboratory of Fuel Cells investigated catalysts without noble and deficient materials for electroreduction process of oxygen (oxygen (air) electrode) and electrooxidation of hydrogen (fuel electrode). High electrochemical activity, corrosion stability, stable work and non-high cost were as main requirements for electrodes of fuel cells [1,2]. 

Fuel cell Anode catalyst Cathode catalyst... 

R. Liu and E. Smotkin, Array Membrane Electrode Assemblies for High Throughput Screening of Direct Methanol Fuel Cell Anode Catalysts, J. Electroanal. Chem., 535, 49 (2002). 

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