Honored “for fundamental contributions to the electrochemical and thermochemical materials science that advance sustainable energy, for her commitment to the broader international materials community and for being an inspiring colleague and passionate mentor,” Sossina M. Haile presented her lecture on the proton transport characteristics of solid acids and the current status of electrochemical technologies based on these electrolytes.
Dedicated to sustainability, Haile focused her research on fuel cells as a way to store and distribute energy from renewable energy sources. Fuel cells consist of an anode and cathode sandwiched around an electrolyte. Haile’s group introduced solid acid materials as the electrolyte in solid acid fuel cells. In her lecture, Haile described the benefits of using cesium dihydrogen phosphate (CsH2PO4) as the electrolyte.
CsH2PO4, she said, exhibits pure proton transport. “Nothing else goes across this electrolyte,” Haile said. “No water molecules that you might get with a polymer electrolyte membrane system, no electronic short-circuiting as you might get with a ceramic (oxide) electrolyte that’s conducting protons.” The electrolyte is impermeable to liquid fuels such as ammonia, its conductivity is insensitive to humidity, and it is stable up to 280°C. The major technical drawback, however, is that the material is easily dehydrated, Haile said.
Because the fuel cell is operational at 250°C and is impurity-tolerant, a lot of CO can be handled as well as a reasonable amount of H2S and ammonia. While Haile points out challenges that remain in working with the cathode of their solid acid fuel cells, she said, “The performance of the fuel cells is in fact sufficient for commercialization.” Her more recent work is in using CsH2PO4-based electrochemical cells to convert ammonia to hydrogen. A spin-out company called SAFCell is developing the technology for remote power markets and for distributed hydrogen generation.
The David Turnbull Lectureship recognizes the career contribution of a scientist to fundamental understanding of the science of materials through experimental and/or theoretical research. In the spirit of the life work of David Turnbull, writing and lecturing also can be factors in the selection process.