H[sub 2]S Poisoning of Solid Oxide Fuel Cells

Sasaki, Kazunari; Susuki, K.; Iyoshi, A.; Uchimura, M.; Imamura, N; Kusaba, Hajime; Teraoka, Yasutake; Fuchino, H.; Tsujimoto, K.; Uchida, Y.; Jingo, N.

doi:10.1149/1.2336075

Cited by 299 publications

(335 citation statements)

References 18 publications

Supporting

Mentioning

319

Contrasting

Order By: Relevance

“…5,7 However, ScYSZ-Hi reported in our previous work 11 shows that Ni/ScYSZ-based cells can likewise be "pushed" into a longterm degradation regime at similar conditions (gas and temperature) through increased cell overpotential. Consequently, the long-term irreversible degradation for the sprayed Ni/YSZ-based cell, YSZ-Hi-Spr, originally reported by Hagen et al 5 compared to the more stable tape cast laminated and Sc-doped cell (ScYSZ-Low) was not merely a question of ScYSZ versus YSZ, although this difference in composition, together with microstructural differences, can play a role in the initial cell performance loss and the cell overpotential "threshold" at which the irreversible long-term degradation is initiated.…”

Section: High Overpotential H 2 S Test -Eis-mentioning

confidence: 94%

“…externally controlled conditions such as set temperature and fuel composition) one should not expect formation of nickel sulfide (Ni 3 S 2 ) either. 3,7,46,47 However, the given test conditions and values for pO 2-anode-compartment are "overall" numbers for the entire anode utilization volume and do not provide information on exact conditions on the nanometer scale of the anode at -or in the nano-scale vicinity of -the TPB at which the pO 2 , gas composition and temperature can be significantly different. Kishimoto and co-workers reported that the Ni-S system is complex and includes Ni-S eutectics between Ni and Ni 3 S 2 and showed thermodynamic data for the significant increase (∼ doubling) of the solubility of oxygen and sulfur in Ni when increasing the oxygen potential, pO 2 , by one order of magnitude.…”

Section: Post-mortem Analysis Of the Anode Layers-mentioning

confidence: 99%

“…It has been suggested that Ni-zirconia based SOFC anodes containing Sc are more tolerant toward H 2 S poisoning than Ni/YSZ based anodes 5,7 and in this work both short and long term tests were performed to investigate this hypothesis. Tests were mainly carried out at the same set of test conditions (e.g.…”

mentioning

confidence: 93%

See 2 more Smart Citations

Sulfur Poisoning of SOFC Anodes: Effect of Overpotential on Long-Term Degradation

Hauch

Hagen

Hjelm

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

Sulfur impurities in carbon containing fuels for solid oxide fuel cells (SOFC), e.g. natural gas and biogas, typically lead to significant losses in performance due to the sulfur sensitivity of Ni/yttria-stabilized-zirconia (YSZ) anodes for SOFC. Full cells having Ni/YSZ anodes have been characterized during long-term galvanostatic operation in internal reforming gas mixture (CH 4 /H 2 O/H 2 :30/60/10), with 2 ppm H 2 S exposure to the anode for 500 hours at 850 • C, at different current densities. This work focus on the long-term effect of H 2 S exposure over a few hundreds of hours; and describes and correlates the observed evolution of anode performance, over hundreds of hours, with sulfur exposure at low cell overpotential (low current density) and at high overpotential (high current density) with and without H 2 S exposure. For tests at low overpotential with H 2 S exposure only a reversible loss in performance was observed and post-mortem SEM analysis showed an intact Ni/YSZ anode microstructure. For tests at high cell overpotential the H 2 S exposure caused both a reversible loss in performance and an irreversible long-term degradation. Post-mortem SEM analysis of the Ni/YSZ anode from this tests showed increased porosity and lack of percolating Ni in the few microns of the anode closest to the anode/electrolyte interface. Fuel flexibility is an attractive characteristic of solid oxide fuel cells (SOFC). They can for instance be fuelled with carbon containing fuels such as natural gas or fuels derived from biomass. A well-known drawback for the use of carbon containing fuels is the fact that they contain varying amounts of sulfur, which poisons Ni-based SOFC anodes.1-8 Therefore, it is important to investigate the SOFC tolerance toward sulfur poisoning and how it is affected by operating parameters.There are many studies concerning the initial, and mainly reversible, loss in performance occurring at SOFC anodes upon sulfur poisoning as a function of different operating conditions. 4,7-9 Fewer results are reported on the long-term, and often irreversible, loss of performance due to sulfur poisoning, 5,8,10 even though this will inevitably be of high importance for SOFC as an emerging energy conversion technology. In order to establish the acceptable limits for sulfur impurities in carbon containing fuels in order to avoid longterm, irreversible degradation, 5,11 it is necessary to understand how the sulfur impurity tolerance correlate to operating parameters such as gas mixtures, temperature and current density, and indirectly to the cell overpotential.It has been suggested that Ni-zirconia based SOFC anodes containing Sc are more tolerant toward H 2 S poisoning than Ni/YSZ based anodes 5,7 and in this work both short and long term tests were performed to investigate this hypothesis. Tests were mainly carried out at the same set of test conditions (e.g. temperature, current density, fuel) in order to compare Sc-Y co-doped (ScYSZ) and Y doped zirconia (YSZ) Ni cermet SOFC anodes. There are several studies s...

show abstract

Section: High Overpotential H 2 S Test -Eis-mentioning

confidence: 94%

Section: Post-mortem Analysis Of the Anode Layers-mentioning

confidence: 99%

See 1 more Smart Citation

Sulfur Poisoning of SOFC Anodes: Effect of Overpotential on Long-Term Degradation

Hauch

Hagen

Hjelm

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…It is already known that sulfur species adsorb onto the surface of Ni anode catalysts when H 2 S is mixed into fuels, 19,20 resulting in both electrode and internal reforming reactions being deactivated. As a result, oxygen ions passing through the electrolyte contribute to oxidation of the anode Ni, rather than the electrode reactions necessary for fuel cell operation.…”

Section: Degradation During the Shutdown Protocolmentioning

confidence: 99%

SOFC Durability against Standby and Shutdown Cycling

Hanasaki

Uryu

Daio

et al. 2014

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

To simulate realistic operating conditions in SOFC systems, we investigate the influence of thermal cycling on the performance of electrolyte-supported planar SOFCs. Thermal cycling is often associated with interruption of fuel supply, with three main modes; hot standby, cold standby, and shutdown. Cell performance degradation is most significant during shutdown cycles. Nickel oxidation and agglomeration are more pronounced when SOFCs are subjected to lower temperatures for longer periods of time, leading to significant performance degradation. Ostwald ripening at the anode leads to degradation as Ni grains increase in size with cycling. Ni particle precipitation on the anode zirconia grains and along electrolyte grain boundaries is found for the first time in shutdown cycling tests. When H 2 S is mixed with the fuel, the internal reforming reactions and electrode reactions are inhibited by sulfur poisoning of the Ni anodes, accelerating degradation. The SOFC cycling degradation mechanisms are discussed in detail. Solid oxide fuel cells (SOFCs) have several advantages including high efficiency, fuel flexibility, and utilization of non-noble metal, Pt-free catalysts, due to their relatively high operation temperature. Commercialization of SOFC systems for residential electric power applications began in Japan in 2011. Such systems are frequently stopped and restarted in normal operation, e.g. when power is not required, or in an emergency. Such start-stop operation results in thermal cycling, and is often associated with an interruption in fuel supply. Although it is well known that thermal and redox cycling under startstop operation deteriorates SOFC electrochemical performance, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] there are only a limited number of studies that systematically focus on this technologically relevant issue.Continuous SOFC stack operation with constant power output generally results in a gradual degradation in performance during long-term operation (SOFCs should run for up to a decade). However, SOFCs can suffer to a greater degree from changes in operation conditions. Due to thermal expansion mismatch between the different components, the cells can suffer from mechanical degradation mechanisms, such as delamination and crack formation with simple thermal cycling. Changes in atmosphere can result in more serious degradation. The influences of thermal cycling and current density cycling on cell degradation have been previously investigated.1-4 The change in volume causes Ni agglomeration. [5][6][7] Redox cycles are typically associated with oxidation of Ni particles at the anode. [8][9][10][11][12] Furthermore, redox cycling results in the formation of Ni hydroxides at a certain vapor pressure in oxidizing atmosphere, with a high water vapor concentration. 13,14 In real residential SOFC power units, cells and stacks are not subjected to these different conditions independently; the changes occur much more dynamically. Therefore, cycle durability studies should be performed using reali...

show abstract

“…Although these reduction and oxidation mechanisms are not fully understood, it is generally accepted that the reactions follow different stages and involve more than one reaction path. Therefore, the reaction kinetics at the interphases strongly depends on chemical and structural properties of the cell components [6,[11][12][13], the electrode morphology (particle size, porosity, thickness, etc.) [14], the characteristics at the interfacial boundary [15,16] and other working parameters as the operation temperature and the gas partial pressure [17].…”

Section: The Role Of the Electrode/electrolyte Interphase In A Sofcmentioning

confidence: 99%