Abstract:

Solar-driven thermochemical production of chemical fuels using redox active oxides has emerged as an attractive means for storing solar energy for use on demand. In this process a reactive oxide is cyclically exposed at high temperatures to an inert gas, which induces partial reduction of the oxide, and to an oxidizing gas of either H2O or CO2, which reduces the oxide, releasing H2 or CO. The capacity for fuel production is dictated by the thermodynamic properties of the oxide, specifically the enthalpy and entropy of reduction. We compare the thermochemical fuel production behavior of a variety of oxides, including those of the fluorite structure-type (ceria and its derivatives) and those of the perovskite structure-type (La1-xSrxMnO3). A shared characteristic of the most promising materials is that bulk oxygen diffusion (chemical diffusion) is fast such that fuel production rates are limited either by surface reaction kinetics or, at high temperatures, gas-phase mass flow rates. We develop an analytical model to treat the behavior under gas-phase limited behavior and explore the implications on fuel production rates.

Biography:

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 in 1992. Sossina Haile’s research broadly encompasses materials, especially oxides, for sustainable electrochemical energy technologies. She has established a new class of fuel cells with exceptional performance for clean and efficient electricity generation, demonstrated electrochemical cells for hydrogen production from electricity for long-term energy storage, developed routes for distributed conversion of ammonia to clean hydrogen to support a hydrogen delivery infrastructure, and created new thermochemical approaches for harnessing sunlight to meet rising energy demands. She has published approximately 200 articles and holds 14 patents on these and other topics. Amongst her many awards, in 2008 Sossina Haile received an American Competitiveness and Innovation Fellowship from the U.S. 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.” In 2008 she was named by Newsweek Magazine as one of 12 people to watch, and in 2020 she was awarded the Turnbull Lectureship of the Materials Research Society. She is a fellow of the Materials Research Society, the American Ceramics Society, and the African Academy of Sciences, and a corresponding Fellow the Ethiopian Academy of Sciences