Piotr Zelenay, Ph.D. Los Alamos Laboratory Materials Sceince and Application Division
The presentation is devoted to platinum group metal-free (PGM-free) electrocatalysts as an alternative to the state-of-the-art low-PGM catalysts for oxygen reduction reaction (ORR) in the polymer electrolyte fuel cell (PEFC) cathode. In the past decade, PGM-free catalysts, especially those obtained by heat-treating precursors of transition metals, nitrogen and carbon, have gradually narrowed the performance gap to precious metal-based materials already used in fuel cell cars. We will review the of PGM-free catalyst development at Los Alamos National Laboratory (LANL) as part of the newly formed Electrocatalysis Consortium (ElectroCat). These approaches include efforts aimed at improving the ORR active-site density and electrode porosity via the use of pore-forming agents and sacrificial templates. We will also describe research specifically targeting better understanding of the sources of catalytic activity in Fe-based PGM-free catalysts and possible ORR active sites as an important step towards rational design of future catalysts. The results from both theoretical modeling and experiment will be presented. Of a number of both in situ and ex situ techniques used for gaining a better insight into the origins of ORR activity in PGM-free catalysts, we will concentrate on the microscopic and X-ray absorption spectroscopic methods, as well as on the implementation of molecular dioxygen analogues as probes for the ORR active sites on the catalyst surface, which promises to make otherwise bulk techniques surface-specific. This part of the presentation will include research performed in close collaboration with LANL's ElectroCat partners. Time permitted, we will report on the activity and durability of catalysts derived from transition metals other than Fe, specifically, Co, Mn and Ni, studied by modeling and experimental methods. Finally, we will present a few highlights from a continuing comparative study of the degradation of PGM-free and low-PGM catalysts in the fuel cell cathodes.