Among items appearing in this issue are the following:

In the second part of a three-part paper discussing recent advances in fuel cell technology, Tom Ralph and Martin Hogarth of the Johnson Matthey Technology Centre, describe further improvements to the operation of proton exchange membrane fuel cells. These have been brought about by enhanced tolerance of the anode to the reformate fuel and extended durability of the membrane electrode assembly. The anode improvements have been achieved by advances in the design and construction of the platinum-based electrocatalyst layers - bilayer anodes being particularly effective for air bleed operation. In addition, a water electrolysis electrocatalyst has been introduced to the anode to improve cell reversal tolerance. Anode designs based on platinum-ruthenium and platinum-molybdenum alloys are examined under typical operating conditions. The third part of this paper will look at challenges presented in the development of the direct methanol fuel cell.

Platinum and palladium behave in an unexpected manner when cathodically polarised in the presence of electrolytes dissolved in carefully dried polar organic solvents, such as N,N-dimethylformamide. A reductive layer is formed on the surface of the metal, the thickness of which depends on the amount of electricity consumed during electrolysis. The reactions and the layers have been studied by Jacques Simonet and Charles Cougnon at the Laboratoire d’Electrochimie Moléculaire et Macromoléculaire, Université de Rennes, France, using a large range of tetraalkylammonium salts and alkali metal iodides as electrolytes. New types of phases (resembling Zintl phases but with a specific insertion of electrolytes) were formed and their oxidation led to great changes in the appearance of the metal surface.

A team of scientists from the Université du Québec à Montréal, INRS-Energie et Matériaux and Institut de recherche d’Hydro-Quebec, Canada, have succeeded in producing nanocrystalline Ti_xFe_yRu_zO_n powders by ball milling. When the O:Ti ratio was > 1, the Ru atoms were in an hexagonal phase but at O:Ti < 1, Ru was in a cubic phase. Electrodes made from the powders had increased capacitance, of up to ca. 60 F g^-1 on cycling in acid or alkali media, and up to 110 F g^-1 if Al was used in the ball milling. The crucial factors for improving the capacitance of Ru-containing materials are the electrochemical behaviour of the matrices used to dissolve the Ru and the prevention of Ru agglomeration.

A summary of the main features in "Platinum 2002" of the supply and demand for the platinum group metals in 2001 is included. Amongst other things, this annual Johnson Matthey publication shows how international factors, mine outputs and the market price of the metals combine to affect metal usage by manufacturers in many industries.

Adding small amounts of rare earth elements to palladium strengthens it. The strengthening effects are discussed by Yuantao Ning of Kunming Institute of Precious Metals, Yunnan, China. He makes use of known phase diagrams of palladium-rare earths, the alloying behaviour of palladium with the rare earths and the atomic (or ionic) size effects of the alloying components. Physical properties, such as solid solubilities of the rare earths in palladium, transition temperatures of intermediate phases and eutectic temperatures in these systems, are influenced by the atomic (or ionic) size of the rare earth elements. A parameter, H_s, the product of the relative difference in atomic weights and the relative difference in atomic radii between a rare earth and palladium, is used to examine the solid solution strengthening effects caused by dilute rare earths. As the behaviour of palladium with the rare earths after alloying are quite similar, the data could be used to predict behaviour in unexamined palladium systems.

The issue also contains a selection of abstracts of the most recently published literature and patents.

The issue ends with a brief discussion in ‘Final Analysis’ by David E. Grove on fixed bed catalyst reactors. He discusses various design factors for the catalyst, gas flow and reactor structure that affect the production of a high purity gas.

Platinum Metals Review is available on the internet from the publications section of the Platinum Today site or from the host site Ingenta Select.

Susan V. Ashton
Editor

Anyone with an active interest in the platinum group metals and their uses who does not have ready access to a copy of Platinum Metals Review and who may benefit from reading it, is invited to request a specimen copy from:

The Editor, Johnson Matthey PLC, Orchard Road, Royston, Hertfordshire SG8 5HE, United Kingdom; Fax +44 (0) 1763 256359; Email jmpmr@matthey.com