After intense years of great development, the electrochemical technologies have become very suitable alternatives in niche markets like industrial wastewater reclamation and soil remediation. A key role to achieve a high efficiency in such treatments is played by the characteristics of the coating of the electrodes employed. This paper compares three techniques, namely immersion, painting and electrophoresis, for the preparation of IrO2-Ta2O5ǀTi, so-called dimensionally stable anodes (DSA(®)). The quality of the coatings has been investigated by means of surface and electrochemical analysis. Their ability to generate hydroxyl radicals and degrade aqueous solutions of hydrocarbons like phenanthrene, naphthalene and fluoranthene has been thoroughly assessed. Among the synthesis techniques, electrophoretic deposition yielded the best results, with DSA(®) electrodes exhibiting a homogeneous surface coverage that led to a good distribution of active sites, thus producing hydroxyl radicals that were able to accelerate the degradation of hydrocarbons.

In this study several types of stainless steel, 304, 310, surfacemodified 304 and 316, and 304 coated with TiN, were evaluated for corrosion resistance in simulated acidic fuel-cell media in order to determine their capacity for use as flow-field plates. The TiN coating was produced in an industrial sputtering operation. The modification of stainless steels 304 and 316 a hydrous oxide film was done by cycling of potential in 1M NaOH. Stainless steel 310 might perform satisfactorily as a bipolar plate. The behaviour of the nitrided material suggests the potential of this coating process.Fuel cells can continuously convert chemical energy directly into electrical energy with high efficiency and practically no contaminant emissions. In order to be competitive with the energy-generation devices already available, issues related to cost, performance and durability of fuel-cell components must be solved (1). Among the more critical components of a fuel cell are the Bipolar Plates (BP), which provide the mechanical support of the membrane electrode assembly (MEA) and simultaneously connect electrically the adjacent cells in a stack, conduct the reactant gases to the electrodes through flow-field channels, and evacuate the water formed at the cathode. This means that they are exposed to oxidizing conditions on one side and reducing conditions on the other (2, 3). Because of the many functions of a bipolar plate in a fuel cell, the selection of the material from which this element is made is a crucial decision. It must be corrosion-resistant but electrically conductive, light and strong, impermeable to water and reactive gases, thermally conductive and economical. Considering these requirements, the choice of materials is limited and involves an optimization process.In general, bipolar plates can be made of metallic or carbon-based materials. One of the first materials used for bipolar plates was graphite, and it is still used in laboratory prototype fuel cells. Unfortunately, graphite has poor mechanical properties; this means that it is not easy to machine, which makes it prohibitively expensive for large-scale production. Metals like aluminum, nickel or steel are susceptible to corrosion in a fuelcell environment; the dissolved metal ions can diffuse to the membrane, diminishing ionic conductivity and affecting water transport through the membrane. Stainless steels are frequently studied to replace graphite, mainly because their high corrosion resistance. The drawback of stainless steels is that its protection against the environment is due to the development of an oxide layer that can be highly resistive, which can affect negatively the fuel-cell performance. Because of these problems, metallic plates must be coated with a corrosion-resistant and yet conductive layer. Among the coatings being explored are conductive polymers, noble metals, metal nitrides, metal carbides and metal oxides (4). The coating process has a decisive effect on the resistance against corrosion. Micropores and microcracks in the protective laye...

In this investigation we used pulse electrodeposition to prepare electrodes suitable for membrane electrode assemblies (MEA) in PEM fuel-cell applications. Platinum can be deposited directly onto a Nafion-bonded carbon electrode from an aqueous solution consisting of hydrogen dinitrosulfatoplatinate (II). The average platinum particle diameter is considerably larger than desired. Further work is needed to optimize the Pt particle size. We studied the durability of Pt/C and Pt/MWCNT using an accelerated durability test (ADT). In this test we observed Pt particle dissolution. Multi-wall carbon nanotubes used as the Pt support exhibit excellent performance in corrosion tests.

In a Proton Exchange Membrane Fuel Cell (PEMFC), the bipolar plates are exposed to oxidant conditions on one side and reducing conditions on the other. The requirement of good electrical and thermal conductivity, good corrosion resistance, low weight, a good impermeability to the reactant gases and low cost restricts the choices of materials to manufacture bipolar plates. The objective of this research is to determine the corrosion resistance of candidate bipolar plate materials in the chemical environment encountered in PEM fuel cells. Several austenitic stainless steels (SS304 and SS316) and nickel alloys have been examined (Inconel 600, Inconel 601, Inconel 625, Incoloy 800H). The out-of-stack tests involved two types of electrochemical measurements, made in solutions that simulate the atmospheres of both the cathode and the anode chambers of a typical fuel cell, bubbled with O 2 and H 2 , respectively, at room temperature and at 50 °C.

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