Welcome to our solid state ionics and electrochemistry research group!
2013.03.09 - Zhao had his ECS proceedings article accepted for publication, congratulations!
2012.09.27 - Prof. Bishop wins IUMRS-ICEM2012 Young Investigator Gold Award
2012.09.04 - Calvert Barclay has joined as a visiting researcher for 2 months
2012.08.31 - Dr. Nicola Perry has joined our group as a postdoctoral researcher
2012.08.30 - Our cover article in PCCP was published
2012.02 - Zhao won an award for his poster presentation on Mn-ceria at the Hydrogen symposium in Kyushu University
- S. R. Bishop, D. Marrocchelli, F. Wang, K. Amezawa, K. Yashiro, and G. Watson, Reducing the chemical expansion coefficient in ceria by addition of zirconia, Energy and Environmental Science, v. 6, no. 4, pgs. 1142-1146 (2013)
- D. Marrocchelli, S. R. Bishop, H. L. Tuller, G. W. Watson, and B. Yildiz, Charge localization increases chemical expansion in cerium-based oxides, Physical Chemistry Chemical Physics, v. 14 pgs. 12070-12074 (2012)
- S. R. Bishop, T. S. Stefanik, and H. L. Tuller, Defects and Transport in PrxCe1-xO2-d: Composition Trends, Journal of Materials Reseearch (2012)
- D. Marrocchelli, S. R. Bishop, H. L. Tuller, and B. Yildiz, Understanding chemical expansion in non-stoichiometric oxides: ceria and zirconia case studies, Advanced Functional Materials, v. 22 no. 9 pgs. 1958-1965 (2012)
- D. Chen, S. R. Bishop, and H. L. Tuller, Praseodymium-cerium oxide thin film cathodes: Study of oxygen reduction reaction kinetics, Journal of Electroceramics, v. 28, pgs. 62-69 (2012)
- H. L. Tuller and S. R. Bishop, Point Defects in Oxides: Tailoring Materials Through Defect Engineering, Annual Reviews of Materials Research, v. 41 pgs. 369-398 (2011)
Fuel cell intro.
Fuel cells provide a way to convert fuels, such as hydrogen or even gasoline, directly to electricity without thermodynamic limitations of internal combustion engines, thereby having very high efficiencies. Additionally, solid state ionic gas permeation membranes allow very high selectivity in separating, for example, H2 from CO2, needed for CO2 concentration and sequestration. In our research, we focus on improving the performance of fuel cells and gas separation membranes by developing new materials with control of properties on the atomic and nanoscale regions.
The following figure shows how a solid oxide fuel cell (SOFC) operates. Oxygen gas is introduced into the lattice as oxide ions (taking up electrons) at the cathode. The oxide ions migrate through the electrolyte to the anode side, where they react with hydrogen, forming water, and releasing their electrons. The electrons flow through the outer circuit, providing current and hence electrical power.
The efficiency of an SOFC is maximized by reducing the resistance to reactions at the electrodes (anode and cathode) and resistance to oxide ion migration in the electrodes and electrolyte. The figure below shows a plot of voltage (V) versus current (i) for an SOFC. There is an open circuit voltage (OCP), when no oxide ions are flowing through the cell, arising from the chemical potential of the reaction for oxygen and hydrogen. As oxide ions are allowed to migrate through the cell (increasing current and generating power) the voltage goes down due to resistances. Ideally, the resistance is small, leading to only a slow decrease in voltage. However, in reality, large resistances do exist as discussed above, resulting in steeper voltage drops. One area of our research is in studying the origin of these high resistances, particularly at the cathode, and discovering ways to minimize them.