Catalyst supports corrosion

Catalyst, Catalyst-Support, and Membrane Material Impact on Maximum Catalyst-Support Corrosion Rate Under Fully Developed H2 Starvation Conditions. Here, Advanced-Support is a Hypothetical Support with a 30-Fold Lower Corrosion Rate than Graphitized Vulcan Carbon and Membrane-X Refers to a Hypothetical Membrane with a 10-Fold Lower 02 Permeability. 

Schulenburg H et al (2011) 3D imaging of catalyst support corrosion in polymer electrolyte fuel cells. J Phys Chem C 115(29) 14236-14243... 

On the basis of the author s approach have been investigated the impact of the injection of CO into the anode feed stream of a PEMFC on the long-term (at least 600 h) MEA performance degradation, under current-cycled operation representative of transport application conditions. First is proposed an elementary kinetic mechanism within MEMEPhys describing the transient behavioiu of a PEMFC MEA in the presence of CO at the anode, and accounting at the same time for the carbon catalyst-support corrosion phenomena in the cathode. In the anode side, competitive CO/H2 adsorptions and electro-oxidations on Pt are accoimted for, as well as the local anodic ORR and the detailed descriptions of the cathodic ORR and the cathodic carbon corrosion. ... 

The membrane electrode assembly (MEA) is the heart of a fuel cell stack and most likely to ultimately dictate stack life. Recent studies have shown that a considerable part of the cell performance loss is due to the degradation of the catalyst layer, in addition to membrane degradation. The catalyst layer in PEMFCs typically contains platinum/platinum alloy nanoparticles distributed on a catalyst support to enhance the reaction rate, to reach a maximum utilization ratio and to decrease the cost of fuel cells. The carbon-supported Pt nanoparticle (Pt/C) catalysts are the most popular for PEMFCs. Catalyst support corrosion and Pt dissolution/aggregation are considered as the major contributions to the degradation... 

Franco, A. A. et al. 2008. Carbon catalyst-support corrosion in polymer electrolyte fuel cells mechanistic insights. ECS Transactions 13 35-55. 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

As COR and OER occur simultaneously in the cathode, their kinetics are particularly important in evaluating carbon-support corrosion. The kinetics of OER is material-specific, dependent on catalyst composition and electrode fabrication.35,37 -39 A number of OER kinetics studies were done on Pt metal electrodes.37-39 However, there is a lack of OER kinetics data on electrodes made of Pt nano-particles dispersed on carbon supports. Figure 2 shows the measured OER current density with respect to the overpotential defined by Eq. (6).35 The 02 concentration was measured at the exit of a 50-cm2 cell using a gas chromatograph (GC). The 02 evolution rate (= 02 concentration x cathode flow rate) was then converted to the OER current density, assuming 4e /02 molecule. Diluted H2 (10%) and a thicker membrane (50 p,m) were used in the measurement to minimize H2 crossover from anode to cathode, because H2 would react with 02 evolved at the cathode and incur inaccuracy in the measured OER current density. Figure 2 indicates that the OER... 

One of the most controversial issues in AFCs is the formation of carbonates. It is generally accepted that the C02, both originally in the air and formed by corrosion reaction of the carbon catalyst support, interacts with the electrolyte according to the following equation ... 

High purity binary oxides such as BeO, MgO, AI2O3, Ti02, And stabihzed zirconia are sintered under pressure to produce high density ceramic ware, particularly cracibles and other containers for use in nonferrous metallurgy and other specialized applications where temperature resistance and corrosion are a problem. Titania is also formed in honeycomb arrays for use as catalyst supports. 

Foamed carbon has 600 times the thermal insulation capacity of the same weight of firebrick and is therefore used as a self-supporting thermal insulation material in furnaces or in fire-retarding sandwich-constructions. Foamed carbon cores are used in foundry technology, because they are easily produced and can be easily removed by combustion from inaccessible cavities. Furthermore foamed carbon is utilized as a filter material for the filtration of corrosive materials, as sintered plugs in gas inlets, as an electrode material and as a catalyst support. 

Polymers, especially poly(styrene-divinylbenzene), have been applied often as catalyst supports, providing the means for using well-defined catalytic groups in a phase separate from that holding the reactants and thereby minimizing the difficulties of product purification and corrosion associated with homogeneous catalysis. Polymers offer several advantages as catalyst supports (1) they are easily functionalized, especially when... 

Wang J, Yin G, Shao Y, Zhang S, Wang Z, Gao Y (2007) Effect of carbon black support corrosion on the durability of Pt/C catalyst. J Power Sources 171 331-339 Maass S, Finsterwalder F, Frank G, Hartmann R, Merten C (2008) Carbon support oxidation in PEM fuel cell cathodes. J Power Sources 176 444-4.51... 

Li W, Lane AM (2009) Investigation of Pt catalytic effects on carbon support corrosion of the cathode catalyst in PEM fuel cells using DEMS spectra. Electrochem Commun 11 1187-1190... 

High resolution transmission electron microscopy (TEM) (Jeol lOOCX) was employed to determine the size of the metal particles on the surface of the catalyst support, and the composition of individual metal particles was ascertained (for thin sections cut with an ultramicrotome) using a field-emission scaiming transmission electron microscope (STEM) (VG HB 501) (at 1.5 mm resolution) and an energy dispersive X-ray (EDX) analyser. The metal loading of catalysts was determined by ICP-AES (Spectro D), following dissolution in concentrated hydrochloric and sulphuric acids. Direct analysis of aqueous samples taken from the reaction medium, using the same analytical technique, allowed the corrosion of metallic components from the catalyst surface to be studied. 

In addition to loss of the platinum, the carlxm support that anchors the platinum crystallites and provides electrical coimectivity to the gas-diffusion media and bipolar plates is also subject to degradation. In phosphoric acid fuel cell, graphitized carbons are the standard because of the need for corrosion resistance in high-temperature acid environments [129], but PEM fuel cells have not employed fully graphitized carbons in the catalyst layers, due in large part to the belief that the extra cost could be avoided. Electrochemical corrosion of carbon materials as catalyst supports will cause electrical isolation of the catalyst particles as they are separated from the support or lead to aggregation of catalyst particles, both of which result in a decrease in the electrochemical active surface area of the catalyst and an increase in the hydrophUicity of the surface, which can, in turn, result in a decrease in gas permeability as the pores become more likely to be filled with liquid water films that can hinder gas transport. 

Phenolic resin foam is an interesting material for the cellular insulation industry because of its high temperature resistance, fire resistance, and very low smoke generation [16]. The aqueous resole is crosslinked in the presence of a surfactant and a low boiling liquid, that volatizes during the increase ofviscosity or plasticity of the mixture. The surfectant is necessary to develop a uniform fine cellular foam stracture [1,6], Carbonization of phenolic foams yields carbon foams with an excellent thermal resistance, that are applied as high temperature insulation materials for the production of filters for corrosive agents and catalyst supports [1]. 

PEM fuel cells require catalysts for both cathode as well as anode reactions. Platinum nanoparticles are the conventionally used catalysts. Conventionally, Pt-nanoparticles are dispersed on a support material such as carbon black. The support material should have properties such as high-electronic conductivity, surface area and corrosion resistance. CNTs, owing to their superior properties, can provide superior performance as catalyst support. Superior cell performance and lifetime have been reported for Pt-nanoparticles-coated CNTs catalyst layers [160-162]. In addition, the presence of CNTs in the catalyst layer provides superior connectivity and easy charge transport. The requirement of high cost catalysts (platinum and its alloys) for both cathodic and anodic reactions makes them unsuitable for commercial applications. Development of efficient catalysts with reduced cost has drawn considerable scientific elforts. Recently, defective... 

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