Methane Decomposition and Carbon Growth on Y2O3, Yttria-Stabilized Zirconia, and ZrO2

Kogler, Michaela; Köck, Eva‐Maria; Perfler, Lukas; Bielz, Thomas; Stöger-Pollach, Michael; Hetaba, Walid; Willinger, Marc Georg; Huang, Xing; Schuster, Manfred Erwin; Klötzer, Bernhard; Penner, Simon

doi:10.1021/cm404062r

Cited by 46 publications

(94 citation statements)

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“…5b. Kogler et al 45 also concluded in their experimental study that methane dissociation is possible on pure YSZ oxides, which efficiently promotes methane-induced growth of different carbon species. Amorphous carbon was identified as a dark layer without a clear structure, which covered the anode surface.…”

Section: Resultsmentioning

confidence: 96%

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

Subotić

Schluckner

Stöckl

et al. 2016

J. Electrochem. Soc.

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Auxiliary power units (APUs) running on carbon-containing fuels provide solutions for high-efficient power supply and emission reduction. In order to ensure safe operation, unwanted degradation caused by carbon depositions should be avoided or controlled. Early detection allows trigerring of counteractions and avoids rapid deterioration of the cell performance as well as mechanical degradation of the cell microstructure and it is presented here. This study also shows that carbon does not only block the active catalyst sites and porous gas channels thus deteriorating the cell performance, but massive carbon depositions lead to destruction of the lattice YSZ-structure. In order to prolong the lifetime of the investigated cells, carbon-dioxide is tested as a possible agent for gasification of deposited carbon. Supplying with CO 2 gasifies carbon to carbon-monoxide, but experimental investigations show further degradation of the cell performance and a reduced methane conversion rate. A method, which represents a combination of CO 2 fed to the anode and an overvoltage applied to the cell, enabled complete performance regeneration in a cell-protecting manner. Solid oxide fuel cells are high-efficient devices, which convert the chemical energy of gaseous fuels directly into electrical energy without additional conversion steps. The heat losses occurring during the operation at temperatures between 600-1000• C can be used as a high-quality heat energy. SOFCs offer a great fuel flexibility and compared to other fuel cell types they can internally reform hydrocarbons. Internal conversion of carbon-containing fuels over nickel as the most widely used catalyst tends to promote carbonaceous deposits on the anode surface as well as inside the anode, causing deactivation of the fuel cells.1-3 The usage of other alternative materials such as Cu-, Gdand Sm-stabilized ceria-based materials or conducting oxides is possible to suppress carbon depositions, but Ni still offers a considerably better conductivity and electrocatalytic performance. 4-7Carbon deposition.-To date many researchers have investigated SOFC anode degradation. Khan et al.8 made a short review of Ni-YSZ degradation mechanisms, classifying these into four types: nickel coarsening, coking, redox instability and sulfur poisoning. A detailed analysis of challenges for nickel steam-reforming catalyst for industrial application can further be found in study from Sehestad.9 However, regarding operation of Ni-YSZ based SOFCs, if the cell is operated under expected conditions, which exclude sulfur in the fuel and the presence of oxygen on the anode side, redox instability and sulfur poisoning can be excluded as possible degradation phenomena. Nickel coarsening is a process where metal powder begins to sinter and small particles grow in size. It reduces the cell conductivity and worsens the cell performance. The sintering of nickel is also known to prone carbon formation, which requires prevention of this mechanism in order to reduce carbon build. 9 Coking can lead to an i...

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Section: Resultsmentioning

confidence: 96%

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

Subotić

Schluckner

Stöckl

et al. 2016

J. Electrochem. Soc.

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“…Even though completely different mechanisms are taking place, e.g., on CH 4 oxide-specific H abstraction from methane by active surface entities capable of binding H 2 in combination with gas-phase radical reactions at T > 1000 K takes place, 17,19 whereas for CO, the inverse Boudouard reaction, which is likely mediated by surface-reduced centers/oxygen vacancies, is responsible for the low final impedance value.…”

Section: Resultsmentioning

confidence: 99%

“…Carbon deposition is visible starting at T > 1023 K (Figure 2, drop of the total transmittance). Especially at higher temperatures ( T > 1173 K)—as in methane 17 —the transmittance drops to zero while the impedance reaches ohmic resistance, caused by a conducting carbon layer. At lower temperatures ( T < 1173 K) the surface chemistry is dominated by formate formation (br-formate: ν as (OCO) = 1595 cm –1 , δ(CH) = 1382 cm –1 , ν s (OCO) = 1332 cm –1 , ν(CH) = 2856 cm –1 ).…”

Section: Resultsmentioning

confidence: 99%

“…These oxides have recently been found to be interesting for forming different carbon architectures following treatment in methane. 17 This will not only directly reveal the already anticipated different formation mechanisms of the carbon deposits but also clarify to which extent the transformation of a carbon fuel into CO-containing syngas mixtures will affect the oxide component of a realistic SOFC material. The discussion is hereby restricted to the carbon growth in pure CO as a benchmark system.…”

Section: Introductionmentioning

confidence: 96%

“…The latter has in a previous study been determined to be one of the most crucial parameters for characterization of the deposited carbon layers. 17 …”

Section: Introductionmentioning

confidence: 99%

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High-Temperature Carbon Deposition on Oxide Surfaces by CO Disproportionation

et al. 2016

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Carbon deposition due to the inverse Boudouard reaction (2CO → CO2 + C) has been studied on yttria-stabilized zirconia (YSZ), Y2O3, and ZrO2 in comparison to CH4 by a variety of different chemical, structural, and spectroscopic characterization techniques, including electrochemical impedance spectroscopy (EIS), Fourier-transform infrared (FT-IR) spectroscopy and imaging, Raman spectroscopy, and electron microscopy. Consentaneously, all experimental methods prove the formation of a more or less conducting carbon layer (depending on the used oxide) of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in flowing CO at temperatures above ∼1023 K. All measurements show that during carbon deposition, a more or less substantial surface reduction of the oxides takes place. These results, therefore, reveal that the studied pure oxides can act as efficient nonmetallic substrates for CO-induced growth of highly distorted graphitic carbon with possible important technological implications especially with respect to treatment in pure CO or CO-rich syngas mixtures. Compared to CH4, more carbon is generally deposited in CO under otherwise similar experimental conditions. Although Raman and electron microscopy measurements do not show substantial differences in the structure of the deposited carbon layers, in particular, electrochemical impedance measurements reveal major differences in the dynamic growth process of the carbon layer, eventually leading to less percolated islands and suppressed metallic conductivity in comparison to CH4-induced graphite.

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A review on coke management during dry reforming of methane

Muraza

Galadima

2015

Int. J. Energy Res.

302

139

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Summary The dry (CO2) reforming of methane is a great promising technology, particularly because of its dual advantages of natural gas valorization and mitigating global warming via carbon dioxide sequestration. However, coke management is the most difficult problem in commercialization of the process. We have therefore examined in this paper the various catalytic systems being evaluated for the dry reforming with emphasis on operating parameters, activity, and coke deposition. Other factors such as the catalyst promoter, the reactor system, and the periodical regeneration were also critically reviewed. The benefits of utilizing methane from natural gas and other sources, where carbon dioxide is considered as an impurity component, are emphasized. Structured basic catalysts, with periodic regeneration certainties, are strong candidates for industrial applications. Therefore, efforts to build commercial scales for the benefit of global energy industries were highlighted. Copyright © 2015 John Wiley & Sons, Ltd.

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Methane Decomposition and Carbon Growth on Y₂O₃, Yttria-Stabilized Zirconia, and ZrO₂

Cited by 46 publications

References 47 publications

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

Strategy for Carbon Gasification from Porous Ni-YSZ Anodes of Industrial-Sized ASC-SOFCs and Effects of Carbon Growth

High-Temperature Carbon Deposition on Oxide Surfaces by CO Disproportionation

A review on coke management during dry reforming of methane

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