Study of Operating Parameters for Accelerated Anode Degradation in SOFCs

Abstract

Solid oxide fuel cell (SOFC) applications require lifetimes of several years on the system level. A big challenge is to demonstrate such exceptionally long lifetimes in ongoing R&D projects. Accelerated or compressed testing are alternative methods to obtain this. Activities in this area have been carried out without arriving at a generally accepted methodology. This is mainly due to the complexity of degradation mechanisms on the single SOFC components as function of operating parameters. In this study, we present a detailed analysis of approx. 180 durability tests regarding degradation of single SOFC components as function of operating conditions. Electrochemical impedance data were collected on the fresh and long-term tested SOFCs and used to de-convolute the individual losses of single SOFC cell componentselectrolyte, cathode and anode. The main findings include a time-dependent effect on degradation rates and the domination of anode degradation for the evaluated cell types and operating conditions. Specifically, the steam content as determined by fuel inlet composition, current density and fuel utilization was identified as major parameter, more important than for example operating temperature. The obtained knowledge is adopted to identify optimal operation profiles in order to acquire accelerated testing for lifetime investigation of SOFCs.

Achievements of NEDO Durability Projects on SOFC Stacks in the Light of Physicochemical Mechanisms

“…The present results on the anode degradations are different from those obtained from button cells [22][23][24] or those anodesupport cells/stacks fabricated and operated mainly in Europe [39][40][41][42][43][44]. Some trends in the anode degradations can be extracted from observations in the previous and the present NEDO projects as following categories: (i) those stacks which do not use alloys in the anode compartment exhibit essentially no degradation (MHPS, Kyocera, NGK).…”

“…Thus, the water vapor pressure becomes another factor to be checked. This may provide one factor of explaining the correlation found by Ploner et al [39,53]. (iii) For Ni/GDC cermets, chemical interactions between the Gd oxide and other components (Ni etc.)…”

“…This may provide one factor of explaining the correlation found by Ploner et al. , . For Ni/GDC cermets, chemical interactions between the Gd oxide and other components (Ni etc.) can be expected.…”

Multi-physics modeling assisted design of non-coking anode for planar solid oxide fuel cell fueled by low steam methane

“…Internal methane steam reforming (MSR) is very appealing as it is helpful for increasing the system efficiency and reducing the system complexity [1][2][3][4]. To reap the full benefit of internal MSR operations, however, using methane with low steam content as the fuel is required so that the consequence of reduced power density and increased heating requirement with high steam content fuel may be prevented [5,6].…”

“…To realize the use of low steam methane fuel, materials to avoid anode coking are critically important and are actively pursued [3][4][5][6][7][8][9][10][11][12][13][14]. A common approach to avoid anode carbon deposition is to eliminate the use of Ni in the anode [5][6][7][8][9][10]. Alternatively, methods of modifying the Ni containing anode with coking resistant material are developed [4,[11][12][13][14][15].…”