Carbon supported PtBi catalysts for direct formic acid fuel cells

Carbon supported PtBi bimetallic catalysts (PtBi/C) prepared by depositing Bi on a commercial Pt/C catalyst and by codeposition of Pt and Bi have been compared for formic acid oxidation in a multi-anode direct formic acid fuel cell. Both types of catalyst gave much higher cell performances than the Pt/C, with only low amounts of Bi (Pt to Bi mole ratios of 11:1 and 14:1, respectively) required for optimum performance. The high Pt to Bi ratio for the best codeposited catalyst indicates that the Bi was concentrated at the surface, and this is consistent with X-ray diffraction and X-ray photoelectron spectroscopy results. However, cyclic voltammetry revealed a strong electronic effect that is inconsistent with surface decoration. The effects of the Bi have been attributed to selective blocking of sites at which CO is formed.

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► Codeposited PtBi catalysts are superior to Bi decorated Pt for formic acid oxidation.
► Very little Bi is required for optimum activity.
► Surface alloying appears to greatly suppress CO poisoning of Pt sites.