NU 2017-176
Inventor
Sossina Haile*
Short Description
Intermediate-temperature solid oxide fuel cells.
Background
Over the past several years, important strides have been made in the development of protonic ceramic fuel cells (PCFCs), devices which offer the potential of environmentally sustainable and cost-effective electric power generation. They are have garnered particular attention because of the high conductivity of the electrolyte at the highly desirable intermediate temperature of 400-600 C. However, the power output from these devices has lagged behind predictions based on electrolyte conductivity. This low performance is due, in part, to the poor rate of oxygen electroreduction at the cathode. Further, the reactive nature of protonic ceramic electrolytes to CO2, has precluded their use with carbon containing fuels such as natural gas and propane.
Abstract
Northwestern researchers have developed new compositional variants for the components of protonic ceramic fuel cells (PCFCs) as well as advanced processing methods that, together, result in record power output for such devices. Specifically, to address outstanding stability and processability challenges with known electrolytes, they explored new electrolyte compositions in the barium zirconate – barium cerate class, ultimately finding BaZr0.4Ce0.4Y0.1Yb0.1O3 (BZCYYb4411) to provide the ideal combination of properties. To enhance oxygen electroreduction kinetics at the cathode, they employed a high activity cathode, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), not previously considered in PCFCs. Their careful evaluation of this material showed that it has high proton solubility and transport rates, extremely favorable characteristics for use in a PCFC. Further, based on their hypothesis that poor contact between the porous cathode component and the pin-hole free electrolyte might contribute to the high resistance values in previously reported PCFCs, they took critical steps to enhance the contact between these two components. Specifically, they applied a thin dense interlayer film of the cathode material on the electrolyte component prior to depositing the porous cathode. The resulting cells deliver substantial (>0.5W/cm2) power output at 500°C along with unprecedented stability under CO2. These conditions permit the use of relatively in expensive stainless steel auxiliary components and operation on ubiquitious fuels, rendering this technology commercially attractive for the first time.
Applications
Advantages
Publication
Choi S, Kucharczyk C, Liang Y, Zhang X, Takeuchi I, Ji H & Haile S (2018) Exceptional power density and stability at intermediate temperatures in protonic ceramic fuel cells. Nature Energy 3: 202–210.
IP Status
Provisional and PCT applications have been filed.
Scanning electron microscopy images of PBSCF/ BZCYYb4411/ cermet anode fuel cell. (left) Cross-section. (upper right) PBSCF cathode microstructure after sintering at 950°C. (lower right) Expanded view of cross-section showing PLD layer at the cathode of electrolyte–cathode interface.