Degradation behavior of Ni-YSZ anode-supported solid oxide fuel cell (SOFC) as a function of H2S concentration. (6th December 2018)

• Record Type: Journal Article
• Authors: Lee, Ho Seong; Lee, Hyun Mi; Park, Jun-Young; Lim, Hyung-Tae
• Is Part Of: International journal of hydrogen energy. Volume 43:Number 49(2018)
• Page Start: 22511
• Page End: 22518
• Publication Date: 2018-12-06
• Subjects: Solid oxide fuel cell -- Sulfur poisoning -- Ni anode -- Degradation mechanism; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.09.189
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: This study investigated the effect of H2 S concentration (5, 10 and 50 ppm) on the degradation and performance of Ni-YSZ anode supported solid oxide fuel cells. When supplied with hydrogen fuel containing H2 S, the cell voltage dropped rapidly, and with increasing H2 S concentration, voltage drop % increased (due to higher sulfur coverage on the Ni surface) and saturated more rapidly. A high concentration (50 ppm) of H2 S led to an additional, slow rate voltage loss. In all cases, cell performance did not completely recover even after being supplied with H2 S-free hydrogen fuel, because of the incomplete desorption of sulfur from the Ni surface. After the performance tests, nickel sulfides were detected on the Ni surface by Raman spectra, which were produced by the reaction of the remaining adsorbed sulfur with Ni during the cooling process. This indicates that the formation of nickel sulfides was not responsible for the secondary voltage drop. SEM/EDS analyses combined with FIB revealed that the reason for the additional 2 nd drop was Ni oxidation; at a high sulfur coverage ratio (50 ppm), the outer layer of the Ni particle was oxidized by oxygen ions transported from the electrolyte. This indicates that H2 S concentration as well as current density is a critical factor for Ni oxidation, and gives rise to the second voltage drop (irreversible cell degradation). The present work showed that the degradation behavior and phenomenon can differ significantly depending on the concentration of H2 S, i.e., permanent changes may or may not occur on the anode (such as Ni oxidation) depending upon H2 S concentration. Highlights: The dependency of the degradation behavior of SOFC on H2 S ppm was investigated. 50 ppm of H2 S led to an additional voltage loss at a slow rate. The incomplete recovery led to the formation of Ni sulfides at low temperatures. The additional voltage drop was attributed to Ni oxidation. H2 S ppm is a critical factor in the secondary drop rate as well as current density.