Improved Fuel Cell Oxidation Catalysis in Pt_1−<i>x</i>Ta_<i>x</i>

Abstract

Sputter codeposition of platinum and tantalum is used to generate catalyst libraries of Pt1−xTax with 0.05< x <0.9. Extensive characterization of the libraries by high-energy X-ray diffraction reveals the presence of several ordered intermetallic phases as a function of composition and deposition conditions. Assessment of the activity toward the oxidation of methanol and formic acid is achieved through a fluorescence-based parallel screening, followed by detailed testing of the most promising catalysts. Correlations among the electrochemical results, the inferred phase fields and X-ray photoelectron spectroscopy characterization provide an understanding of the catalytically active surface and highlight the utility of composition spread thin films in catalyst research. The observations suggest that the interaction between Pt and Ta suboxides is important and enhances the catalytic activity of Pt.