Platinum Metals Review - Volume 41, Issue 3, 1997

Proton exchange membrane fuel cells operating on hydrogen/air are being considered as high efficiency, low pollution power generators for stationary and transportation applications. There have been many successful demonstrations of this technology in recent years. However, to penetrate these markets the cost of the fuel cell stack must be reduced. This report details the progress made on reductions in the stack cost by lowered platinum catalyst loadings in the latest stack designs, the development of lower cost membrane electrolytes, the design of alternative bipolar flow field plates, and the introduction of mass production technology. Despite such advances, there is still a need for further reductions in the stack cost, through improvements in the performance of the membrane electrode assembly. However, improved stack performance must be demonstrated not only with pure hydrogen fuel but also, more particularly, with reformate fuel, where tolerance to poisoning by carbon monoxide and carbon dioxide needs to be improved. Advances that are required in the ancillary sub-systems are also briefly considered here.

Oxygen is an immensely important chemical species — essential for life. The need to determine levels of oxygen occurs in many diverse fields. In environmental analysis, oxygen measurement provides an indispensable guide to the overall condition of the ecology and it is routine practice to monitor oxygen levels continuously in the atmosphere and in water. In medicine, the oxygen levels in the expired air or in the blood of a patient are key physiological parameters for judging general health. Such parameters should ideally be monitored continuously, which may present problems. Determining oxygen levels in blood requires blood samples which may be difficult to take or impossible to take regularly — the elderly suffer from collapsed veins, while babies may only have 125 cm³ of blood. The measurement of oxygen levels is also essential in industries which utilise metabolising organisms: yeast for brewing and bread making, and the plants and microbes that are used in modern biotechnology, such as those producing antibiotics and anticancer drugs. Here, the background to oxygen measurements is described and work to develop new optical oxygen sensors which utilise the luminescence of platinum metals complexes is discussed.

The syntheses and catalytic behaviour of rhodium catalysts encapsulated in zeolites are reported. Several parameters are investigated in this catalyst system, including the auxiliary ligands and the zeolite supports used. It is demonstrated that the zeolite support can be crucial in determining the types of products formed from catalytic hydroformylation reactions. The results are rationalised in terms of fundamental principles of organometallic chemistry. This enhances the understanding of these catalyst systems at a molecular level and demonstrates that a synergy exists between the development of new, efficient catalyst systems and understanding chemistry at a fundamental level.