Electron carbon powder

As described above, XAS measurements can provide a wealth of information regarding the local structure and electronic state of the dispersed metal particles that form the active sites in low temperature fuel cell catalysts. The catalysts most widely studied using XAS have been Pt nanoparticles supported on high surface area carbon powders,2 -27,29,so,32,33,38-52 represented as Pt/C. The XAS literature related to Pt/C has been reviewed previ-ously. In this section of the review presented here, the Pt/C system will be used to illustrate the use of XAS in characterizing fuel cell catalysts. 

Pt/Ru electrocatalysts are currently used in DMFC stacks of a few watts to a few kilowatts. The atomic ratio between Pt and Ru, the particle si2 e and the metal loading of carbon-supported anodes play a key role in their electrocatalytic behavior. Commercial electrocatalysts (e.g. from E-Tek) consist of 1 1 Pt/Ru catalysts dispersed on an electron-conducting substrate, for example carbon powder such as Vulcan XC72 (specific surface area of 200-250 m g ). However, fundamental studies carried out in our laboratory [13] showed that a 4 1 Pt/Ru ratio gives higher current and power densities (Figure 1.6). 

Highly monodispersed platinum-based nanoparticles Pt, Pt-Ru, Pt-Ru-Sn ° were synthesized by y- or electron beam-radiolysis and then deposited onto Vulcan carbon powder with high loadings (up to... 

The directives apply to all materials used in the make up of electrical and electronic components and include paint, plastics, adhesives and rubbers, plastic parts, protective coating materials, epoxy adhesives, cyanoacrylate adhesives, polyurethane adhesives as well as complete computer motherboards. Computer and peripheral equipment are made up of different materials consisting of plastic, ferrous and non-ferrous metals, trace heavy metals, glass, foams, rubber, carbon powder and additives. Other non-metal materials posing environmental and health problems present in electrical and electronic products are beyond the scope of this book and will not be discussed here. The supportive components used in these products fall within the following ten product categories in the directive which are ... 

Bessel and Rolison reported the electrochemical behavior of [Co(SALEN)]2"1" and Fe(bpy)3]2+ in zeolite Y.[1571 They prepared an electrode using the complex-zeolite composite and carbon powder, and tested the electrochemical behaviors of the electrode and the composite dispersed in a solution. It was found that the electrochemical behaviors of these two materials differ to a great extent. After several cycles, the former loses all the electrochemical signals, whereas the latter continuously shows the signals. They believed that the electrochemical signals arise from the complex attached onto the zeolite external surface (defects or external supercages), whereas the complex inside the zeolite channel does not participate in electron transfer of the electrochemical process. In fact, there has been dispute on whether the electrochemical signals arise from electron transfer in zeolite channels or from those complexes on the zeolite external surface. Both views can find experimental support.1158 1591... 

The physical state of carbon material in a fuel cell can be of two kinds (i) relatively massive electrodes in the shape of plates or rods. Electrodes of this type may be cut out of graphite or pressed from powdered carbon materials (usually, with different binders), and may, at the same time, serve as current collector and as consumable electrode (ii) highly disperse carbon powders, present as slurry in the liquid carbonate electrolyte, which constantly come in contact with a metal electrode, serving as current collector, where they take part in the electrochemical reactions with electron transfer. 

The device studied by the Laboratoire Centre de Recherche THOMSON-CSF uses H3OUO2PO4.3H2O (HUP) as solid electrolyte and various activated carbons (NORIT RBX or CORAX L6) . Before use, the carbon powders are thermally treated at 400 °C in vacuum in order to remove impurities that are absorbed on the surface or arise from incomplete carbonation. These defects lower the electronic conductivity and complicate the redox reactions. 

The microporous carbon used by Ash et al. (1963) was prepared by compressing carbon powder into a tube of 3mm internal bore. The plug has the following properties, L = 0.91cm, porosity = 0.5, and the cross sectional area of 0.07 cm. The electron microscopy shows the particle to have a pore size of 100 A. Each particle consists of an assembly of para-crystallites. They found that the surface diffusion in the steady state measurement increases rapidly as the monolayer coverage is approached. As the monolayer layer is exceeded the diffusion coefficient shows a minimum and then rises sharply again in the region of capillary... 

In conclusion, because of the electrochemical importance of the electrode-electrolyte interface, it is necessary to consider the chemical and mechanical compatibility of a candidate electrolyte material with the electrodes required for a given application. For a typical cathode region in a battery, in which active cathode material together with a small proportion of carbon powder to enhance electronic conductivity is incorporated in a matrix of ionically conducting polymer electrolyte, it may also be necessary to consider materials compatibility problems that arise at the cathode compartment-current collector interface. Finally, compatibility problems can arise with inter-cell insulating layers and also with encap-sulant materials. 

Carbon materials have received great attention in the last decades with the emergence of nanoscience area [75]. The utilization of carbon nanomaterials also possibilities the increase on charge transfer in bioelectrochemical devices. These includes the modification of electrodes with several kinds of carbon at nanometer range carbon powder, carbon nanotubes, graphene sheets and carbon capsules [76-78]. The investigation of electronic properties of carbon nanotubes since their discovery by lijima and co-workers [79] in 1991 are one of the most reported... 

Negative electrode carbon is normally powder with particle size range of 5-20 pm. As carbon particles must receive electrons from external circuit and Li-ions from liquid electrolyte, the carbon particles have to contact both the metal current collector and the electrolyte liquid. Carbon powder is mixed with PVDF binder and then coated by a machine onto a thin metal copper foil, as shown in Figure 12.1.1. 

The catalyst ink usually includes catalyst, carbon powder, binder, and solvent. Sometimes, other additives are added to improve the dispersion of the components and stabilize the catalyst ink. The catalyst either covers the surface of the GDL or directly coats the surface of the membrane (catalyst coated membrane, CCM). The CL usually consists of (1) an ionic conductor such as perfluorosulfonate acid (PFSA) ionomer to provide a passage for protons to be transported in or out, (2) metal catalysts supported on a conducting matrix like carbon, to provide a means for electron conduction, and (3) a water-repelling agent such as polytetrafluoroethylene (PTFE) to provide sufficient porosity for the gaseous reactants to be transferred to catalyzed sites [5, 6]. Every individual factor must be optimized to provide the best overall performance of a CL. 

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