Nanostructured Low-Temperature Solid Oxide Fuel Cell with High Power Density
Authors: An Jihwan , Kim Young-Beom , Park Joonsuk , Gur Turgut M. , Prinz Fritz B. 
Published: February 2020

Obtaining high power density at low operating temperatures has been an ongoing challenge in solid oxide fuel cells (SOFC), which are efficient engines to generate electrical energy from fuels. This article presents a pathway to significantly reduce the operating temperature of SOFC while achieving exceptionally high power density that is of practical interest. A multi-prong strategy was pursued in this study that included thin film fabrication as well as surface modification suing atomic layer deposition (ALD). Remarkably high power densities up to 1.3 W/cm2 at 450 oC demonstrated in this work overcomes several major technical hurdles that stand in the way of achieving superior cell performance and may open up new possibilities for low temperature SOFCs to expand their areas of application, e.g., as in portable devices and systems [1].

This result was partly made possible by three-dimensional (3-D) nanostructuring of the ultra-thin (60nm) electrolyte interposed with a nano-granular catalytically active interlayer at the cathode/electrolyte interface, all of which contributed to the high surface reaction rate. For creating the nanostructure, we have developed a nanosphere lithography (NSL) technique, which is significantly simpler for making ordered nanostructures than conventional MEMS techniques used commonly. The NSL method was used on a single crystal Si wafer platform to fabricate a 3-dimensional self-standing cell architecture, which included fully functioning, pinhole-free and conformal sub-100 nm electrolyte layer that minimizes ionic transport loss through the membrane. The membrane electrode assemblies (MEA) were furnished with porous platinum electrodes deposited on the external surfaces to serve as cathode and anode layers. In addition, an ultrathin functional interlayer of yttrium-doped ceria (YDC) film was employed to modify the cathode interface in order to provide further improvement of the cathode reaction kinetics. Moreover, we found that the nano-granular surface microstructure of the interlayer is beneficial in lowering the polarization loss by nearly 1/3 at the cathode interface by enhancing the oxygen reduction reaction. In this presentation we will describe the cell fabrication process, and discuss the results of current-voltage measurements as well as electrochemical impedance spectroscopy (EIS) in order to characterize cell performance and behavior. Also, the results of transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (EDS) used for the characterization of the MEA components will also be discussed.

Acknowledgment

Y.-B.K. is grateful to the National Research Foundation (NRF) of the Korean Ministry of Education, Science, and Technology (MEST) (Grant No. 2012R1A1A1014689 and 2012R1A6A1029029) for its financial support. J.A., T.M.G., and F.B.P. gratefully acknowledge partial support from the Center on Nanostructuring for Efficient Energy Conversion (CNEEC) at Stanford University, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001060.

References

[1] J. An, Y.B. Kim, J. Park, T.M. Gür and F.B. Prinz, Nano Lett. 13(9), pp. 4551-4555 (2013)