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The combinatorial chemical screening of large numbers of samples has received much attention in recent years, particularly due to its use in drug discovery for the identification of new leads, although the approach has been used for about twenty years to find new inorganic materials. The technique is now being adapted and applied to finding new materials (1).

Direct methanol fuel cells (DMFCs) have an advantage over other fuel cells in converting methanol directly at the anode to electricity, but poor performance has limited their commercialisation, the major limitations being anode and membrane performances (2). Combinatorial screening can be used to find more active electrochemical catalysts, but presently-used current-voltage methods are time-consuming and cumbersome for such large numbers of samples. In other combinatorial screenings, a fluorescent indicator has been used to detect the presence of ions (such as H⁺), the intensity of the fluorescence being an indication of activity.

Now, fluorescent detection and combinatorial chemistry have been used by scientists at Pennsylvania State University, Illinois Institute of Technology and ICET in Massachusetts to identify a combination of platinum group metals with improved properties, which they say may be used as the anode in a DMFC (3).

Platinum, ruthenium, osmium, iridium and rhodium were combined in a 645-electrode array, deposited onto carbon paper and screened in a methanol/fluorescent indicator medium. The most active components were selected; bulk samples were characterised by various techniques and tested as anode catalysts in DMFCs. The best combination was Pt(44)/Ru(41)/Os(10)/Ir(5), which had a current density 40 per cent higher than presently used Pt-Ru at 400 mV and more than double the value under short circuit conditions.

With this method a wide range of compositions was searched rapidly and thoroughly, allowing areas of apparent inactivity to be investigated. In fact, the activity of this particular combination does not lie in the expected active regions. Such optical screening may be useful to identify other electrochemical materials.

The Development of Platino-Calixarenes

In the January 1998 issue of Platinum Metals Review, on page 15, right hand column, the seventh line should read “obtained by reacting complex 3 with 4,4′-bipyridine, see Scheme V.” In the legend of Scheme V L* must be replaced by 3.

Polymers of Platinum Metals Complexes Immobilised on Electrodes

In the April 1998 issue of Platinum Metals Review, on page 61, right hand column, the thirteenth line should read “[Rh(bpy)(PPh₂Et)₂(Cl)(H)]⁺”.