High Energy Ballmilled Pt-Mo Catalysts for Polymer Electrolyte Fuel Cells and Their Tolerance to CO

Catalysts containing Pt and Mo were synthesized by high energy ballmilling. The two metal powders were milled together in one step with a leacheable dispersing agent (Al or ) and a leacheable process‐control agent (NaF or ) to increase the specific area of the catalysts and avoid sticking of the catalyst's precursor on the vial walls and grinding balls. The catalysts were labeled and to reflect the bulk atomic or molecular nominal content of the milled powders. After the leaching step, the actual bulk Mo content of both catalysts was rather low (∼5 atom %). Despite their low Mo content, both catalysts displayed a similar performance, in fuel cell tests, to that displayed by black from Johnson Matthey. The best catalyst in was , which is a face‐centered cubic solid solution of Mo (∼5 atom %) in Pt with a specific area of . By combining X‐ray diffraction, X‐ray photoelectron spectroscopy, and fuel cell test results, it was possible to determine that Pt was metallic in the catalyst, but that Mo(V and VI) were present at the surface of the working anode in . © 2000 The Electrochemical Society. All rights reserved.