Degradation Phenomenon of Ni-YSZ Anode Support Cells Under Various Operating Conditions

Abstract

Solid oxide fuel cells (SOFCs) is an electrochemical device which can directly convert chemical energy to electrical energy. They have many advantages including the high efficiency and multi-fuel flexibility. [1,2] Although high temperature-SOFCs have advantages in terms of performances high production cost and the limited durability are one of issues for making commercialization of SOFCs. Generally, SOFCs are required over 40,000 h life-time to enter into the real markets. [3,4] Furthermore, SOFCs should produce electrical power stably under a variety of severe operating conditions, such as thermal cycle, sudden electrical load change, and frequent electrical load cycle. In this study, various accelerating degradation testing are performed to find the degradation patterns and disclose the main degradation mechanism of SOFCs. The durability of SOFCs are tested on a variety conditions of load trip and load cycle. The load trip is cycled at the current density of between 0 and 200 mA cm-2 at 700oC. Each step is held at 12 h and repeated 30 times. The load cycle is cycled under the current density of between 120 and 200 mA cm-2 at 700oC. Each step is held at 12 h and repeated 12 times. The thermal cycle is tested at 700oC and ramped down at 1℃ min-1 to 400oC. This step is repeated 30 times. As a periodic diagnostic tool of I-V (current-voltage) characterization and electrochemical impedance analysis are performed cells, using an electrochemical impedance spectroscopy (EIS) with a Potentiostat/Galvanostant device using a frequency range from 1 MHz to 1Hz. The physicochemical analysis of tested cell are carried out using field emission-scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). 1. Steele, Brian CH, and Angelika Heinzel. "Materials for fuel-cell technologies."Nature 414.6861 (2001): 345-352. 2. Yamamoto, Osamu. "Solid oxide fuel cells: fundamental aspects and prospects." Electrochimica Acta 45.15 (2000): 2423-2435. 3. Khan, Muhammad Shirjeel, et al. "Fundamental mechanisms involved in the degradation of nickel–yttria stabilized zirconia (Ni–YSZ) anode during solid oxide fuel cells operation: A review." Ceramics International 42.1 (2016): 35-48. 4. Hagen, Anke, et al. "Durability study of SOFCs under cycling current load conditions." Fuel Cells 9.6 (2009): 814-822. * Corresponding author: jyoung@sejong.ac.kr (J.-Y. Park).