High-Throughput Evaluation of Dealloyed Pt-Zn Composition-Spread Thin Film for Methanol-Oxidation Catalysis

While the high energy density of methanol makes it a promising fuel for low-temperature fuel cells, the lack of an oxidation catalyst with sufficiently fast kinetics limits the commercial implementation of these fuel cells. The numerous adsorption and charge-transfer steps associated with complete methanol oxidation make metal alloys likely candidates for superior catalysts. Combinatorial searches employing metal thin-film libraries are well suited for methanol-oxidation catalyst studies, and we have developed experimental techniques to strengthen the evaluation of such libraries in a high-throughput regime. In particular, we employ catalyst pretreatment methods and linear sweep voltammetry with a ferrocene redox couple to determine the area and thus the specific activity of kinetically stable alloy catalysts. Particular attention is given to the relevance of the assessment to fuel cell operating conditions. These methods, combined with established techniques, provide both a rapid semiquantitative map of methanol-oxidation activity and enable a detailed quantitative analysis of the most active compositions. The efficacy of these techniques is demonstrated through the evaluation of Pt-Zn continuous composition-spread thin-films of varying thickness. The detailed characterization of the thin films is presented and discussed in the context of the electrochemical analysis.