Speaker Information

Dr. Shawn Litster
Carnegie Mellon University 

Title: Advanced Materials Characterization and Development for Polymer Electrolyte Electrolyzers and Fuel Cells

Abstract: Electrification of transportation and industry is vital to building a resilient, efficient, and flexible energy infrastructure that reduces air pollution, including particulate emissions that are a significant health hazard. However, many sectors are challenging and economically demanding to electrify, such as heavy-duty ground transportation, aviation, and industries like ammonia, steel, petroleum refining, synthetic fuels, and cement production, is crucial in tackling efficiency and environmental pollution. Utilizing hydrogen with low carbon intensity is a key strategy for lessening the reliance of these sectors on fossil fuels and reducing emissions. The first part of this talk will focus on the role of hydrogen in decreasing emissions in these areas, along with the accompanying technical and economic hurdles. There's sustained a worldwide interest in producing low-carbon hydrogen through sustainable electricity sources. Proton exchange membrane water electrolyzers (PEMWEs) play a vital role in this transition due to their high efficiency, rapid response time, and capability to electrochemically compress hydrogen. However, despite encouraging progress, significant materials improvements are necessary to meet ambitious cost targets.
One critical aspect of enhancing PEMWE catalyst performance for achieving high currents at efficient low voltages is minimizing overpotential losses. These losses result from electron, proton, and water transport to the oxygen evolution catalysts. Additionally, there are secondary current-induced loss mechanisms, including membrane and electrode dry-out and ionic contaminant polarization. In this presentation, we will delve into the relevant transport mechanisms and the fundamental limits of reducing these overpotentials. We have evaluated the transport properties of electrodes that are challenging to directly probe due to their micrometer and sub-micrometer length scales using ultra-high-resolution three-dimensional imaging with X-ray computed tomography (nano-CT) and plasma-focused ion beam cross-sectioning with scanning electron microscopy (pFIB-SEM) for image-based simulations. Subsequently, we will briefly review existing methods for experimentally diagnosing transport limitations, as well as highlight new methods currently under development in our laboratory. These new diagnostics include a galvanostatic intermittent titration technique (GITT) for electrolyzers and a new limiting-current diagnostic for PEMWEs. The presentation will conclude by highlighting fresh insights into the significance of two-phase transport, electrode and membrane dry-out, all enabled by these diagnostics and modeling. The presentation will highlight an innovative conductive-additive approach developed in our laboratory to significantly improve performance while simultaneously reducing iridium use.
A vital link exists between PEMWEs and the development of PEM fuel cells (PEMFCs) for heavy-duty transportation. Heavy-duty vehicles present one of the most achievable costs for low carbon hydrogen among the hard-to-abate sectors. Therefore, rapid commercialization of fuel cells for heavy-duty vehicles is a crucial step in increasing low-carbon hydrogen production and driving down costs through economies of scale for low-carbon hydrogen production in other challenging sectors, like ammonia production. Establishing widespread use of PEMFCs in heavy-duty trucks requires significant improvements in efficiency and durability, including achieving the challenging >25,000-hour lifetime while also meeting acceptable values for the total cost of ownership. This talk will highlight our lab’s recent efforts in addressing these challenges and our innovations in materials, imaging, diagnostics, and simulations for PEMFCs. These highlights will include unique ionomer integration strategies, image-based modeling, and the increasing role of machine learning. 
 

Bio: Shawn Litster is a Professor and the Russell V. Trader Faculty Fellow in the Department of Mechanical Engineering an Energy Fellow in the Scott Institute for Energy Innovation at Carnegie Mellon University in Pittsburgh, PA. He also has courtesy appointments in the Departments of Chemical Engineering and Materials Science and Engineering. He received his Ph.D. in mechanical engineering from Stanford University (2008) and his B.Eng. and M.A.Sc. degrees from the University of Victoria in Canada. His current research focus is micro- and nano-scale transport phenomena in energy conversion technologies where electrochemistry and electrokinetics play a dominant role, including fuel cells, electrolyzers, and batteries. His research interests also include multiphase flow in porous media and micro-channels, non-linear dynamics, catalytic gasification, and microfluidic pumping. He is also the director of Carnegie Mellon’s X-ray Computed Tomography Facility. In 2019, he received the US DOE’s award for fuel cell research and development in recognition of his contribution to the development of platinum-free fuel cells. He is a recipient of Carnegie Mellon’s George Tallman Ladd Research Award, a National Science Foundation CAREER award, the University of Victoria’s Lieutenant Governor’s Silver Medal, and best paper/presentation awards from The Electrochemical Society and the American Society for Mechanical Engineers. He is the author of over 100 journal papers and three book chapters. He is also an inventor for three US patents on fuel cell design. He also serves as an Associate Editor for the International Journal of Heat and Mass Transfer.