Cathode Functionalization Via Atomic Layer Deposition for Solid Oxide Fuel Cells

Abstract

Crucial ­­processes in solid oxide fuel cell (SOFC) such as ionic transport and electrode reactions are thermally-activated processes and their kinetics are strongly dependent on the temperature. Despite intense recent efforts to reduce its operating temperature to address durability, cost and applicability issues, it is still an ongoing challenge to deal with the resulting sluggish kinetics and power losses at lower temperatures. On the other hand, while catalysts with higher surface area are preferred for maximized catalysis per mass and volume, these high-surface area catalysts are prone to agglomeration sacrificing its overall catalytic activity during operation. In this talk, we will present a couple of examples how these issues have been successfully addressed by the use of atomic layer deposition (ALD), which has emerged as an important deposition technique for various applications due to its unique atomic-scale deposition capability in a highly controllable fashion at a temperature significantly lower than conventional chemical vapor deposition techniques. We will present several examples of enhancements in cathode performance and/or durability enabled by an ultrathin coating of Y-doped zirconia or ceria (i.e. YSZ or YDC) on different nano-porous cathode materials including Pt, La(Ni,Fe)O3 and (La,Sr)(Co,Fe)O3. In addition, we will report mechanism studies mainly performed via electrochemical impedance spectroscopy and electron microscopy focusing on the shift of the rate-determining step by the ultrathin overcoat. Acknowledgement: The authors gratefully acknowledge Nissan Motor Co. Ltd. and NASA MIRO Program (Grant No. NNX15AQ01A) for their financial support.