Advances in Corrosion-Resistant Ceramic Materials for Fuel Cells

Lior Elbaz, Chemistry, Bar-Ilan University, Ramat-Gan, Israel

Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed and tested to exceed the US DOE lifetime goals of 5000 or 40,000 hrs for transportation and stationary applications, respectively. In addition to their increased durability, the interactions between some new support materials and metal catalysts such as Pt result in increased catalyst activity.

In this talk we will present our recent advances with the synthesis and application of Pt-supported on molybdenum carbide. We will show a novel catalytic synthesis of Pt/Mo₂C, from a physical mixture of solid precursors, which led to the production of unique platinum structures: Nano-rafts, containing less than six atoms of Pt on a molybdenum carbide support. XRD traces obtained on this material show a cubic phase Mo₂C (a=4.225Å) with an average crystallite size on the order of 22-23Å as determined by full profile fitting methods. No evidence of nano-crystalline Pt is evident in this XRD trace as one would typically see on Pt/C catalysts. Electrochemical half-cell tests employing these catalysts for oxygen reduction demonstrate that these structures allow for more efficient utilization of platinum, with higher half wave potential for ORR exhibited for the imbedded Nano-raft based catalysts compared to a traditional, commercial carbon supported catalyst. In addition, significant increase in durability was exhibited with these newly devloped materials. We will present these data along with other results and discuss the impact that the Nano-raft structure has on support durability in half-cell accelerated stress test (AST) measurements.