Reversible Electrochemical Cells for Fuel to and from Electricity
Sossina M. Haile
Department of Materials Science and Engineering, Applied Physics Program, and Department of Chemistry, Northwestern University
Over the past decade, the availability of electricity from sustainable energy sources has risen dramatically while the cost has fallen steeply. These factors have driven a surge in activity in the development of energy storage technologies. While much of this effort has been directed towards photocatalytically generated solar fuels and grid-scale batteries, reversible hydrogen electrochemical cells offer untapped opportunities. In particular, electrochemical cells based on proton conducting ceramic oxides are attractive candidates for interconversion between hydrogen and electricity. The proton conducting nature of the electrolyte provides inherent advantages in the gas flow configuration over traditional solid oxide cells in which the electrolyte is an oxygen ion conductor. We describe here recent progress in reversible protonic ceramic cells achieved using a combination of three advances: a new electrolyte composition, a new air electrode, and processing methods to decrease the contact resistance between these two components. The resulting cells display exceptional performance in both fuel cell and electrolysis modes. In the latter case, conversion efficiency suffers a small penalty due to slight electronic leakage across the cell. The cells are extremely stable over hundreds of hours of operation and dozens of cycles between electricity generation and hydrogen production. As such, protonic ceramic electrochemical cells are likely to play a major role in a sustainable energy future.
Sossina M. Haile is the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, a position she assumed in 2015 after serving 18 years on the faculty at the California Institute of Technology. She earned her Ph.D. in materials science and engineering from the Massachusetts Institute of Technology. Haile’s research broadly encompasses solid state ionic materials and devices, with particular focus on energy technologies. She has established a new class of fuel cells based on solid acid electrolytes, and demonstrated record power densities for solid oxide fuel cells. Her more recent work on water and carbon dioxide dissociation for solar-fuel generation by thermochemical processes has created new avenues for harnessing sunlight to meet energy demands. Haile is a Fellow of Materials Research Society, American Ceramics Society, Africa Academy of Sciences and Ethiopian Academy of Sciences. She is also recipient of many prestigious awards, including an American Competitiveness and Innovation (ACI) Fellowship in 2008 from the National Science Foundation in recognition of "her timely and transformative research in the energy field and her dedication to inclusive mentoring, education, and outreach across many levels"; the 2010 Chemical Pioneers Award of the Chemical Heritage Foundation; and the 2012 International Prize in Ceramics of the World Academy of Ceramics. Her national service includes membership on the National Materials Advisory Board, a committee serving the National Academies of Sciences and of Engineering, from 2005 to 2011; co-authorship of the National Academies study America’s Energy Future: Electricity from Renewable Resources, published in 2009; and membership on the Materials Research Society Board of Directors from 2011 to 2015.