Morphology of carbon supported Pt-Ru electrocatalyst and the CO tolerance of anodes for PEM fuel cells

Two Pt-Ru/C catalysts, a commercial 20% Pt-10% Ru/C and a 10% Pt-5% Ru/C synthesized in house (YZU catalyst), were examined for the CO tolerance in polymer-electrolyte-membrane fuel cells (PEFCs). Both half-cell tests under 250 ppm of CO/H-2 and single-cell tests under 100 ppm of CO/H2 showed that the YZU catalyst had smaller increase in the overvoltage at a given current. The platinum-ruthenium microstructures of these two electrocatalysts in the fabricated electrodes were characterized by X-ray absorption spectroscopy (EXAFS). EXAFS indicated that there was no Pt-Ru metal-metal interaction in the commercial catalyst; instead, only ruthenium oxide signals were observed. On the other hand, the YZU catalyst contains a Pt-Ru bimetallic interaction as indicated by the X-ray absorption spectra. It was considered that the Pt-Ru alloy structure has better CO tolerance than nonalloy Pt-Ru structure.