Co tolerance of Pt-W electrocatalysts for polymer electrolyte fuel cells E. Passalacqua a,* , F. Lufrano a , G. Squadrito a , A. Patti a , L. Giorgi b a CNR-ITAE, via Salita S. Lucia sopra Contesse 5, 98126 S. Lucia, Messina, Italy. b ENEA, C.R. Casaccia, ERG-TEA-ECHI, via Anguillarese 301, 00060 S. Maria Galeria, Roma, Italy (Received) Abstract: The performance of Pt-W electrocatalysts as CO tolerant anodes in polymer electrolyte fuel cells (PEFCs) was evaluated and compared with Pt-Ru, Pt-Sn and Pt anodes. Testing were carried out in pure hydrogen and in presence of 100 ppm CO. CO tolerance was measured as the loss in the cell voltage due to CO in the H 2 normalised to a pure H 2 fed standard anode . A voltage loss less than 25% at 0.6 A/cm 2 was measured at 90°C with Pt 50 Ru 50 /C and Pt 50 W 50 /C anodes. The promising results obtained with Pt-W binary anode catalyst, though non conclusive what concerns the stability render this catalyst interesting for further investigation. Key words: * To whom correspondence should be addressed. Fax: +39 090 624247; e-mail: passalacqua@itae.me.cnr.it 1. INTRODUTION Polymer electrolyte fuel cells for their characteristics of high- energy efficiency and low emissions are the most promising candidates for electric power generator in transportation applications. One of the limitations of these systems is related to safety problems and public acceptance for use of pure H 2 as on- board fuel. At present, the most probable fuel is hydrogen rich gas coming from reformed or partially oxidised fuel, but this gas contains at least 1% of CO [1]. Unfortunately, the performance of the Pt, the most effective catalyst for hydrogen oxidation in PEFC, is seriously depressed from the presence of only 5 to 10 ppm of CO [2, 3]. A reduction of CO content in the reformed fuel can be performed by using specific systems, but a further reduction under 100 ppm creates significant problems in the design of gas clean-up systems [4]. Several strategies have been proposed to overcome CO polarization phenomena in anode compartment of PEFCs. One approach is based on the injection of low levels of O 2 or oxygen-evolving compounds [5, 6] in the fuel anode side to enhance the CO oxidation and avoid the poisoning of the platinum sites. The most common approach to solve the CO poisoning issues is to use tolerant electrocatalysts able to work at very low anode polarization also with at least of 50 to 100 ppm of CO in fuel feed streams. For this reason many efforts in these last years were devoted to the development of CO tolerant electrocatalysts obtained by adding a secondary element to Pt to enhance the electrocatalytic activity on CO electrooxidation. A number of element exhibits a cocatalytic activity for the anodic oxidation of CO, even if today it is state of the art to use an appropriate Pt/Ru alloy as the most active system for CO oxidation [7-10]. Recent studies [11-13] on the Pt-WO x system have demonstrated a cocatalytic activity both for H 2 /CO oxidation attributed to a hydrogen “spill-over” effect on WO 3 together an interaction between H 2 O adsorbed on the WO 3 surface and CO adsorbed on Pt [11-12]. In this paper our recent results on anode catalysts for H 2 /CO Journal of New Materials for Electrochemical Systems 3, 2000 © J. New Mat. Electrochem. Systems