Discovery of fuel cell anode electrocatalysts and dehydrogenation catalysts using combinatorial techniques

A gas diffusion optical screening method was developed for the discovery of catalysts for the electro-oxidation of reformate gas (H₂ with 100 ppm CO). The screening cell was designed to accommodate a gas diffusion layer, 715 member catalyst array, and an electrolyte container. Since protons are generated during H₂ oxidation, a pH sensitive fluorphore was used to identify active compositions. The cell showed no detectable iR drop across the array and ranked activity of two commercial PtRu and one Pt catalysts. Over 95% of a given catalyst fluoresced at the initial onset potential and a 5 mV difference in onset potential of two different catalysts was statistically different. A gas diffusion half cell was designed similar to the optical screening cell to obtain current-potential curves of bulk catalysts. The screening results correlated with half cell and fuel cell data, internally validating the method. The combinatorial method was then applied to search for catalysts in the PtRuMoIrRh composition space. The catalysts on the array were prepared by hydrogen reduction of the metals salts on carbon. The most active catalysts were from the Pt enriched regions of the PtRuMoRh quaternary. Bulk catalysts were prepared from the active regions and tested in the gas diffusion half cell. The most active catalysts in the optical screening were also the most active catalysts in the half cell. When any homemade catalysts were compared to commercial PtRu, however, the performance was worse. A high surface area, high catalyst activity synthetic method is the most important factor to reliably screen catalysts for “real world” fuel cell application.; High surface area catalysts were tested for direct methanol oxidation activity. The optical screening method was compared with disk electrode, high throughput fuel cell testing, and fuel cell testing. Six catalysts examined included two commercial PtRu catalysts, a Pt catalyst, and three homemade PtRu catalysts of varying activity prepared by the Adams and Watanabe methods. The comparison of the techniques demonstrated the disk electrode and high throughput fuel cell testing correlated the most to the fuel cell testing. The optical screening had two levels of distinction, and may still be useful for testing large numbers of catalysts. (Abstract shortened by UMI.)...