characterisation revealed a heterogeneous distribution of deposited Pt on the substrate surface. Most of the deposits were agglomerates of spherical nanoparticles. Local particle densities exceeding IO’O cme2 were observed. From the electrochemical and structural that Pt investigations, it appears electrodeposition on graphite involves several Faradaic steps on the time scale. First, at tcO.3 s, a large number of nanosized dusters are possibly formed, which may be mobile during the electrodeposition process, and assemble in an accidental distribution of Pt agglomerates. Secondly, at ho.3 s, it is very likely that the more rapid growth of a small number of Pt particles gives a transient response. It thus seems that cluster diffusion contributes significantly to the structural evolution of platinum electrodeposits on graphite. F. Gloaguen, J.M. Lbger, C. Lamy, A. Marmann, U. Stimming, R. Vogel: Ektrochimica Acta 44(11) 1805-1816 (January 1999).
novel experimental membrane manufactured by Ballard Advanced Materials Corporation (BAM3Gm 407), with an equivalent weight of 407 g mol-l, These two membranes differ in their chemica structure, equivalent weight and water content. Solid-state electrochemistry shows that the permeability (the product of diffusion coefficient and solubility) of oxygen for the two membrane materials is approximately the same. The solubility of oxygen in the novel BAM3G 407 membrane investigated is lower than that for Nafion 117 by a factor of four. On the other hand, the diffusion coefficient of oxygen in BAM3G 407 is greater by a factor of four. The difference in mass transport properties is explained on the basis of the much higher water content in the BAM3G 407 membrane (87 wt% H,O) compared to N&on 117 (19 WC% H,O). V.I. Basura, I?D. Beattie, S. Holdcroft: J Elrctroanalytical Chemistry 458( 112) l-5 (October 1998).
Oxygen reduction on [email protected]
117 and BAM3GTM 407
Methanol electrooxidation colloidal PtRu-alloy
Mass transport parameters are determined for oxygen reduction in two different proton exchange membranes: (1) [email protected]
117 (Du Pent)-equivalent weight 1100 g mol-‘; and (2) a
The electro-oxidation of methanol on a novel carbon-supported PtRu electrocatalyst produced via colloidal PtRu precursors was investigated by thin-film-electrode (TFE) measurements, and
combinations of a,P,P-trifluorostyrene, substituted a$$-trifluorostyrene and ethylenebased monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in fuel cells. Patent number: US 5834523 Publication he: 10 November 1998 Inventors: A.E. Steck, C. Stone
Applicant: The Dow Chemical Company, USA A composite oxygen electrode/electrolyte structure for a solid-state electrochemical device is described. A porous composite electrode is in contact with a dense electrolyte membrane. The electrode has a porous structure with interpenetrating networks of an ionically conductive material and an electronically conductive material. It also has an electrocatalyst dispersed within its pores. This electrode structure is relatively simple to manufacture, requiring relatively few steps to infiltrate an electrocatalyst precursor material to obtain an electrode structure which will perform well in a solid oxide fuel cell. It also has a relatively low internal resistance, and permits the selection of an optimal electronically conductive material and electrocatalyst. Patent number: WO 98149738 Publication date: 5 November 1998 Inventor: S.A. Wallin
Substituted u$$-trifluorostyrenebased composite membranes Applicant: Ballard Power Systems Inc, Canada A composite membrane is described in which a porous substrate is impregnated with a polymeric composition with various
PEM fluid distribution integral sealing
Applicant: Ballard Power Systems Inc, Canada This fuel cell comprises a pair of fluid distribution layers between a pair of separator plates. At least one of the fluid distribution layers has a sealing region and an electrically conductive, fluid-permeable active region, and a preformed sheet extending into both of these regions. An ion-exchange membrane is interposed between the fluid distribution layers, and an electrocatalyst is interposed between the fluid distribution layers and the membrane, to define the active region. Compression of the preformed sheet by squeezing the pair of plates together renders the fluid distribution layer impermeable to fluids parallel to the major planar surfaces, in the sealing region. The preformed sheet thus has an intrinsic sealing capability. This reduces or eliminates the need for separate gaskets or sealing components, and integrates several functions - such as
compared with commercially available Pt and PtRu catalysts. The PtRu-colloid-based catalyst shows similar activity towards methanol oxidation as other conventional PtRu catalysts. A comparison with literature data from half-cell measurements at similar mass-specific current densities clearly demonstrates the high potential of the colloid-based PtRu catalyst for fuel-cell applications. T.J. Schmidt, H.A. Gasteiger, R.J. Behm: Electrochemistry Communications l(1) l-4 tJanuary 1999).
Ionic conduction of toughened zirconia base composite The effect of alumina addition on ionic conductivity of an alumina/8YSZ composite was examined, in which the conductivity slightly increases with alumina addition. The alumina addition has a role in increasing the 8YSZ18YSZ interface (grain boundary), by suppressing the matrix grain growth as well as increasing the population of the alumina/8YSZ interface. We suggest that the increase in ionic conductivity in the composite is not ascribed to the aluminaJ8YSZ interface, but to the grain boundary. A. Yuzaki, A, Kishimoto: Solid State Ionics 116(1/2) 47 - 51 (January 1999). sealing, fluid distribution and current collection - in a single layer. Patent number: WO 98150973 Publication date: 12 November 1998 Znventorr: D.I? Wilkinson, J. Stumper, S.A. Campbell, M.T. Davis, G.J. Lamont
fuel cell heating
Applicant: Zentrum f3ir Sonnenenergie- und Wasserstoff-Forschung Baden-Wiirttemberg, Germany The patent describes an integral PEM fuel cell heating module. In each cell, the anode is configured as a three-layer anode, with a CO and/or methanol vapour oxidation-selective catalyst layer on the side facing away from the membrane, and an electrochemicaily active layer on the side facing the membrane, in addition to a contact layer made of porous carbon paper between the two layers. The module also comprises a thermally insulating, gas-tight, tubular hollow jacket surrounding the stack, and a methanol reformer. Water vapour and reformer heating are produced by a catalytic residual gas burner. The module also contains a fan inside the hollow jacket, which circulates damp air through the air ducts of the gas distribution layer. The fuel cell heating module is suitable for use in a fuel cell installation for supplying household energy. Patent number: WO 98150975 Publication date: 12 November 1998 Inventors: B. Rohland, J. Scholta, G. Zettisch, W. Epple, V. Plzak