The effect of H2S on the performance of Ni–YSZ anodes in solid oxide fuel cells

Rasmussen, Jens Foldager Bregnballe; Hagen, Anke

doi:10.1016/j.jpowsour.2009.02.001

Cited by 190 publications

(159 citation statements)

References 22 publications

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“…SEM images obtained at 8-10 kV using the secondary electron detector and low-voltage SEM images were obtained at 0.9 kV using the in-lens detector. Lowvoltage in-lens SEM imaging allows percolating and non-percolating Ni to be distinguished in the Ni/YSZ cermet microstructure, as described by Thydén et al [32] and later illustrated several times for long-term tested SOC [7,[33][34][35]. Image analysis by line-intercept-method [36] allowed for determination of the area fraction and particle size distributions of Ni and pores, using the in-house developed Matlab based software, ManSeg.…”

Section: Sem Imagingmentioning

confidence: 99%

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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Cermet Ni/YSZ electrodes are the most commonly applied fuel electrode for solid oxide cells (SOC) both when targeting solid oxide fuel cell (SOFC) applications and when used as solid oxide electrolysis cell (SOEC). In this work we report on the correlation between initial Ni/YSZ microstructure and the resulting electrochemical performance both initially and during long-term electrolysis testing at high current density and high p(H2O) inlet. Especially, this work focuses on microstructure optimization to hinder Ni mobility and migration during long-term operation and illustrates the key-role of electrode over-potential on the degradation of the Ni/YSZ electrodes in SOEC. We find that for long-term stability for electrolysis at high current densities and high p(H2O) the as-produced NiO/YSZ precursor electrode should be: 1) As dense as possible, 2) as fine particle and pore sized as possible and 3) the three phases (Ni, YSZ and pore phase) shall be size-matched and welldispersed. Applying such microstructure optimized Ni/YSZ electrode we show SOEC test results with long-term degradation rate as low as 0.3-0.4 %/kh at 1 A/cm 2 , 800 C and inlet gas mixture of p(H2O)/p(H2):90/10. This enables SOEC operation of such cell for more than 5 years below thermo-neutral potential at these operating conditions.

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Section: Sem Imagingmentioning

confidence: 99%

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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“…The vast literature refers and focusses on systems, which are fed with H 2 S in H 2 -containing fuels. They studied the deactivation mechanisms and materials application Zha et al, 2007;Li T. S. et al, 2009;Li et al, 2010;Hagen, 2009, 2010;Xu et al, 2010;Li and Wang, 2011a,b), summarized in several studies and reviews (Sasaki et al, 2006(Sasaki et al, , 2011Trembly et al, 2006;Gong et al, 2007;Goodenough and Huang, 2007;Sun and Stimming, 2007;Rasmussen and Hagen, 2009;Yang et al, 2010;Cheng et al, 2011;Hagen et al, 2011;Kromp et al, 2012;Hagen, 2013;Wang et al, 2013;Weber et al, 2013;Hauch et al, 2014). The effect of a sulfur-containing fuel is examined on the performance and durability of SOFCs through the variation of several factors, such as the: (i) operating temperature, (ii) applied current/voltage load, (iii) time on stream, (iv) H 2 S concentration and to a lesser extent the concentration of H 2 and H 2 O, and (v) the anodes materials.…”

Section: Introductionmentioning

confidence: 99%

Effect of Au and/or Mo Doping on the Development of Carbon and Sulfur Tolerant Anodes for SOFCs—A Short Review

Niakolas

Neofytidis

Neophytides

2017

Front. Environ. Sci.

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HIGHLIGHTS• The kinetics of CH 4 steam reforming and partial oxidation are determined by the oxidation rate of CH x adsorbed species • The modification of the Ni/YSZ and Ni/GDC with Au and/or Au-Mo results in differentiated structures of atomically dispersed Au and/or Au-Mo at the surface and the bulk of the Ni particles.• At lean S/C NiAu/YSZ selectively oxidizes electrochemically the catalytically produced H 2 and CO, while NiAu/GDC is selective to the direct partial electrochemical oxidation of CH 4 to CO and H 2.• The modified electrodes show significant tolerance to C formation.• Au-Mo modification enhances the intrinsic sulfur tolerance properties of Ni/GDC.The presented work is a short review of the research attempts from our group with collaborators, during the last 15 years, which had as main objective to study and improve the electrocatalytic performance of Ni-based electrode materials for the CH 4 Internal steam Reforming process (ISR.) in Solid Oxide Fuel Cells (SOFCs). In particular, NiO/YSZ and NiO/GDC anode powders were modified with Au and/or Mo nano-particles via different preparation methods. These efforts resulted in anode materials with high tolerance and improved electrocatalytic activity under both carbon forming and sulfur poisoning conditions. The most important findings are being reviewed and critical findings are being highlighted 50 as to stress the key differences in the electrocatalytic performance between Ni/YSZ and Ni/GDC. The possible effects of Au and/or Mo addition on the physicochemical and strucutral properties of the cermets are thoroughly discussed as well as active functional layers in the form of anode SOFC electrodes.

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“…Hagen et al, 5 reported similar findings with anode-supported cells and observed a lower degree of poisoning for Ni-ScSZ based anodes (compared to Ni-YSZ anodes). Rasmussen and Hagen also studied the performance of anode-supported cells for pulse addition of H 2 S. 12 They observed an increasing drop in voltage upto 20 ppm H 2 S in galvanostatic mode. However, as in most other studies z E-mail: vj@iith.ac.in; dmonder@iitb.ac.in they found that the performance drop leveled out once the H 2 S concentration was increased beyond 20 ppm.…”

mentioning

confidence: 99%

Sulfur Poisoning of SOFCs: A Model Based Explanation of Polarization Dependent Extent of Poisoning

Janardhanan

Monder

2014

J. Electrochem. Soc.

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Several experimental studies have shown that, 1) the extent of the poisoning effect due to trace amounts of sulfur compounds in the fuel is lower if a SOFC is operated at a higher current density, and 2) the performance drop due to sulfur poisoning is much lower for Ni-GDC or Ni-ScSZ anodes when compared to Ni-YSZ anodes. This work presents a first principles numerical model that simulates experimental studies of sulfur poisoning on SOFC button cells. The exchange current densities for the electrodes are determined using sulfur-free polarization data for cells fueled by humidified mixtures of H 2 and N 2 . A detailed surface reaction model that predicts the fractional coverage of all adsorbed species at the three phase interface is coupled to the SOFC model and the sulfur coverage is used to alter the anode exchange current density. The resulting model predictions match experimental observations during both galvanostatic and potentiostatic operation. Our analysis shows that the observed lower performance drop at higher current density is due to the non-linear nature of the electrochemical rate equations, and that the lower impact of sulfur poisoning on Ni-GDC and Ni-ScSZ anodes (compared to Ni-YSZ anodes) is due to their higher electrochemical activity. Solid oxide fuel cell (SOFC) systems operating on natural gas or gasified coal can be significantly more energy efficient than today's combustion systems and can thus reduce CO 2 emissions. However, a major problem associated with the use of hydrocarbon fuels is the presence of sulfur containing compounds that are converted to H 2 S under SOFC operating conditions.1 The H 2 S present in the feed gas can readily deactivate conventional Ni cermet anodes. One can certainly have a desulfurization unit before the fuel cell stack to deal with the sulfur poisoning. However, this leads to increased system complexity and decrease in overall efficiency. Nevertheless, it is important to understand and quantify the sulfur tolerance of SOFC anodes in the event of sulfur breakthrough from the desulfurizer. Sulfur poisoning of Ni-YSZ anodes in SOFC is well studied experimentally for model fuel compositions consisting of ppm levels of H 2 S in mixtures of H 2 , H 2 O and an inert 2-4 as well as H 2 S in gas mixtures representative of natural gas or reformed natural gas.5-8 Most of the experimental literature deals with H 2 S concentrations well below 10 ppm and work that treats H 2 S concentrations higher than 20 ppm is rather limited. 2,5,8 On the other hand it is well known that natural gas and biogas can have substantially higher sulfur concentrations and that catalytic steam reforming of methane can be carried out on Ni even with 100 ppm H 2 S without losing all catalytic activity 9,10 e.g., a methane conversion (in model biogas) of ∼35% can be maintained using a supported Ni catalyst with 100 ppm H 2 S at 800• C. 10For an electrolyte supported cell Zha et al., 2 studied the cell performance for a wide range of H 2 S concentrations using DC polarization and electrochemical i...

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The effect of H2S on the performance of Ni–YSZ anodes in solid oxide fuel cells

Cited by 190 publications

References 22 publications

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Effect of Au and/or Mo Doping on the Development of Carbon and Sulfur Tolerant Anodes for SOFCs—A Short Review

Sulfur Poisoning of SOFCs: A Model Based Explanation of Polarization Dependent Extent of Poisoning

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