Mixed conductor anodes: Ni as electrocatalyst for hydrogen conversion

Primdahl, S.; Mogensen, Mogens Bjerg

doi:10.1016/s0167-2738(02)00393-4

Cited by 107 publications

(98 citation statements)

References 17 publications

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“…It was shown that these anodes can reach high performance with Ni-contents as low as 3%. 22 Since LSTN is an electronic conductor, we particularly address this smart material concept of an anode catalyst for novel SOFC and SOEC electrodes. 3,14 In this context, the concept of smart catalysts becomes very important, in order to avoid the poisoning of the reduced Ni-surface and to maintain the nanosized dimensions.…”

Section: Materials Concept For Novel Sofc Anodesmentioning

confidence: 99%

Smart material concept: reversible microstructural self-regeneration for catalytic applications

et al. 2016

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a This paper presents a proof-of-concept study and demonstrates the next generation of a "smart" catalyst material, applicable to high temperature catalysis and electro-catalysis such as gas processing and as a catalyst for solid oxide cells. A modified citrate-gel technique was developed for the synthesis of La x Sr 1À1.5x Ti 1Ày Ni y O 3Àd . This method allowed the synthesis of single phase materials with a high specific surface area, after the first calcination step at temperatures as low as 650 C. Up to 5 at% of nickel could be incorporated into the perovskite structure at this low calcination temperature. X-ray powder diffraction and microscopy techniques have proven the exsolution of nickel nanoclusters under low oxygen partial pressure. The amount of exsoluted nickel nanoparticles was sensitive to surface finishing, whereby much more exsoluted nanoparticles were observed on pre-treated and polished surfaces as compared to original ones. Increasing A-site deficiency leads to a larger number of nickel particles on the surface, indicating a destabilizing influence of the A-site vacancies on the B-site metal cations.Repetitive redox cycles prove that the nickel exsolution and re-integration is a fully reversible process.These materials working in a cyclic and repetitive way may overcome the drawbacks of currently used conventional catalysts used for high temperature systems and overcome major degradation issues related to catalyst poisoning and coarsening-induced aging.

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Section: Materials Concept For Novel Sofc Anodesmentioning

confidence: 99%

Smart material concept: reversible microstructural self-regeneration for catalytic applications

et al. 2016

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“…40,41,49 The direct reaction between H 2 and O 2− on the YSZ followed by electron migration through zirconia to nickel has also been mentioned as a possibility 57 although without strong experimental evidence. 58,59 This indicates that proton migration (diffusion or electrical proton conductions) plays an important role in the ion transfer, and a mechanism involving water adsorbed on YSZ followed by proton migration has been suggested as the main charge transfer mechanism in H 2 O -H 2 mixtures. [40][41][42][43][44] Similar to H 2 O, CO 2 may dissociate on either the nickel or YSZ surface, and a mechanism involving the surface migration of oxide ions over nickel and YSZ may occur in CO 2 -CO mixtures also.…”

Section: D 850ºcmentioning

confidence: 99%

Co-Electrolysis of Steam and Carbon Dioxide in Solid Oxide Cells

Ebbesen¹,

Knibbe²,

Mogensen³

2012

J. Electrochem. Soc.

168

142

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Reduction of H 2 O and CO 2 as well as oxidation of H 2 and CO was studied in a Ni/YSZ electrode supported Solid Oxide Cell (SOC) produced at DTU Energy conversion (former Risø DTU). Even though these Ni/YSZ based SOCs were developed and optimized for fuel cell use, they can work as reversible SOCs in mixtures of H 2 O, H 2 , CO 2 and CO. From polarization (i-V) and electrochemical impedance spectroscopic characterization, it is evident that, electrochemical reduction of both CO 2 and H 2 O occurs during coelectrolysis of H 2 O and CO 2 in these Ni/YSZ based SOC. During co-electrolysis, the equilibrium of the water gas shift reaction is reached, and CO is therefore produced via the water gas shift reaction also. Significant differences during oxidation/reduction in H 2 O -H 2 and CO 2 -CO mixtures were observed implying that different reaction mechanisms apply for the mixtures.

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“…In this case, a small amount of metallic catalyst (e.g. Ni, Ru) can be dispersed into the anode functional layer to improve the electrochemical performance to an acceptable level [37]. As long as the content of the metal is kept low enough (several percent by volume), a detrimental effect associated with the reoxidation of metals can be avoided since any dimensional change of the metal can be tolerated inside the pore structure of the electrode and the rigid ceramic framework will remain intact.…”

Section: Additional Metallic Electrocatalystmentioning

confidence: 99%

Ceramic‐based Anode Materials for Improved Redox Cycling of Solid Oxide Fuel Cells

Tietz

2008

Fuel Cells

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In order to improve the reliability of anode‐supported solid oxide fuel cells (SOFCs) in terms of tolerance to redox cycles, and to minimise fuel preprocessing for the direct use of readily available hydrocarbons in SOFCs, alternative ceramic‐based anode substrate materials and functional anode materials were investigated, with the emphasis on perovskite oxides. Compared to (Sr,La)TiO3–δ and Nb2TiO7–δ, (Sr,Y)TiO3–δ ceramics (SYT, with a Y content of about 7 at.‐%) reduced at high temperatures are promising redox‐stable anode substrate materials due to their very small dimensional change upon redox cycling (0.14%). Correspondingly, the composite ceramic SYT/YSZ impregnated with ∼5 vol.‐% Ni has a good chance of being applied as a redox‐stable functional anode material due to its even smaller dimensional change upon redox cycling (<0.05%) and superior electrochemical performance for H2 oxidation (polarisation resistance ∼0.2 Ω cm2 at 800 °C). The small fraction of Ni homogeneously dispersed on the pore walls of the SYT/YSZ ceramic framework significantly enhances the electrocatalytic activity, and should not have a detrimental effect on the redox stability of the electrode. In addition, two mixed conductors with perovskite structure, (La0.8Sr0.2)0.94Al0.5Mn0.5O3–δ and La0.4Sr0.6Ti0.4Mn0.6O3–δ, were also investigated. They show promising electrochemical performance for the oxidation of H2. However, the high‐level Mn substitution which seems necessary to achieve a significant electrical conductivity and catalytic activity has a detrimental effect on the chemical stability of these two materials. Consequently, they show relatively large and irreversible chemical expansion and are thus not considered to be qualified functional anode materials.

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Mixed conductor anodes: Ni as electrocatalyst for hydrogen conversion

Cited by 107 publications

References 17 publications

Smart material concept: reversible microstructural self-regeneration for catalytic applications

Smart material concept: reversible microstructural self-regeneration for catalytic applications

Co-Electrolysis of Steam and Carbon Dioxide in Solid Oxide Cells

Ceramic‐based Anode Materials for Improved Redox Cycling of Solid Oxide Fuel Cells

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