2009-11-05
New Approaches to Modeling Fuel Cells: Catalytic Activity and Stability in PEMFC and SOFC
From peak oil to global warming to grid stability, a host of issues suggest that our methods for obtaining energy will have to change dramatically over the next few decades. Fuel cells, which generate energy by forming water from hydrogen and oxygen, offer an exciting alternative to many of our present energy related technologies. For instance, Low-temperature Proton Exchange Membrane Fuel Cells (PEMFCs) are a promising technology for reducing oil use through enabling hydrogen powered automobiles. On the other hand high-temperature Solid Oxide Fuel Cells (SOFCs) may provide the ability to generate clean and efficient energy for homes and buildings. An outstanding challenge in the design of fuel cells is that they all
require catalyzing the oxygen reduction reaction, which process puts severe demands on the cathode materials. In this talk I will show how modeling approaches, both continuum and atomistic, can be used to understand and design properties of fuel cell catalysts. In the first part of the talk I will focus on the issue of PEMFC cathode degradation. PEMFC cathode catalysts are usually made of carbon supported Pt or Pt alloy nanoparticles, which have large surface area and high catalytic activity, but show limited stability under fuel cell operating conditions. We have constructed an electrochemical rate model for Pt degradation and demonstrated that surface energy driven instability changes dramatically in the commercially relevant region of 2-5nm diameter particles. We have also discovered that hydrogen crossing over from the anode can dramatically alter the mechanisms and extent of degradation. In the second part of the talk I will focus on SOFC cathodes, which are typically made of perovskite oxides. The oxygen reduction reaction on these materials is still poorly understood and I will describe how first-principles quantum mechanical calculations can give insight into perovskite interactions with oxygen, and potentially provide simple descriptors to help design optimal catalytic activity.
For more information, please visit Prof. Morgan's research group page.