Investigation of Direct Methanol Fuel Cell Electrocatalysts Using a Robust Combinatorial Technique

Abstract

A combinatorial approach to batch fabricating and evaluating fuel cell catalyst surfaces is described. The well-known binary alloy and two compositional regimes of a novel quaternary system were examined in detail. Catalyst films no thicker than 10 nm were deposited onto an array of 36 gold electrodes in area that were microfabricated on a glass substrate. The catalyst films had identical bulk and surface compositions, a result of the atom-level mixing that occurred during the room-temperature cosputtering method used. A multichannel pseudopotentiostat was implemented for electrochemical screening. Compositions with promising and/or contrasting catalytic activities were also studied using X-ray diffraction, X-ray energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. A low-Pt-content film was found to exhibit nominally the same activity (at vs a normal hydrogen electrode in , ) as the best PtRu alloys studied. This material had a fundamentally different crystal and electronic structure than that observed in the films and exhibited a significantly higher degree of Pt site utilization. These results were consistent with the existence of a catalytic reaction pathway different than that reported for .