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Tsyganok, A. I.; Suzuki, Kunio; Hamakawa, Satoshi; Takehira, Katsuomi; Hayakawa, T.

doi:10.1023/a:1012739112430

Cited by 113 publications

(99 citation statements)

References 17 publications

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“…[6] Herein, we synthesized binary Ni-Al-HT with interlayer CO 3 2À anions by a co-precipitation method. [7] After reduction in a H 2 atmosphere at 500 8C, the sample was transformed into a highly dispersed Ni/Al 2 O 3 nanocatalyst (denoted as NiAl 2 O 3 -HT). The molar ratio of Ni to Al, determined by ICP analysis, was 3:1.…”

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confidence: 99%

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

et al. 2012

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Storing hydrogen safely and efficiently is one of the major technological barriers preventing the widespread application of hydrogen-fueled cells, such as proton exchange membrane fuel cells (PEMFCs). Hydrous hydrazine (N 2 H 4 ·H 2 O) is considered as a promising liquid hydrogen storage material owing to the high content of hydrogen (7.9 %) and the advantage of CO-free H 2 produced. [1] In particular, hydrous hydrazine offers great potential as a hydrogen storage material for some special applications, such as unmanned space vehicles and submarine power sources, where hydrazine is usually used as a propellant.The decomposition of hydrazine proceeds by two typical reaction routes: [2] H 2 NNH 2 ! N 2 ðgÞ þ 2 H 2 ðgÞ ð 1Þ 3 H 2 NNH 2 ! 4 NH 3 ðgÞ þ N 2 ðgÞ ð 2ÞReaction (2) not only decreases the yield of H 2 but also complicates the separation process of products, because the ammonia by-product would poison the Nafion membrane and the fuel-cell catalysts. Thereby, it is of crucial importance to develop a highly selective catalyst over which the reaction proceeds only by pathway (1) at low temperatures. To this end, Xu and co-workers [3] synthesized a series of nickelcontaining bimetallic nanoparticles, including Ni-Rh, Ni-Pt, and Ni-Ir, which showed high H 2 selectivity at room temperature. Nevertheless, the incorporation of noble metals to nickel greatly increased the cost of catalysts. In a subsequent study by Xu and co-workers, [4] Ni-Fe nanoparticles were employed as catalysts for this reaction. However, the nanoparticles were only active at 70 8C, and addition of 0.5 mol L À1 NaOH was necessary for the high selectivity. Moreover, the practical application of colloidal nanoparticles will raise significant problems, such as mass production, handling, stability, separation, and recyclability. Therefore, from the viewpoint of practical applications, a supported base metal catalyst is a preferred choice owing to its low cost, good mechanical stability, and easy separation from the reaction medium.Herein, using a Ni-Al hydrotalcite-like compound (Ni-Al-HT) as the precursor, we obtained a highly dispersed nickel catalyst that presented 100 % conversion of N 2 H 4 ·H 2 O and up to 93 % selectivity to H 2 for the decomposition of N 2 H 4 ·H 2 O at ambient temperature. To our knowledge, this is the first report in which supported base metal catalysts show such high selectivity towards the formation of H 2 .It is well-known that supported noble metal catalysts, especially iridium catalysts, are very active for the decomposition of hydrazine. Compared with Ir, Ni is less active. [5] Accordingly, to obtain a high activity over Ni catalysts, a very high loading of Ni is required while maintaining a high degree of dispersion. Hydrotalcite-like compounds have been demonstrated to be excellent precursors for the preparation of highly dispersed and high-loading metal catalysts. [6] Herein, we synthesized binary Ni-Al-HT with interlayer CO 3 2À anions by a co-precipitation method. [7] After reduction in a H 2 atmosphere at...

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A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

et al. 2012

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“…Reactions at with very short residence times over Rh _ Ni bimetallic catalyst under conditions in which O2 was not totally converted found high activity of the Rh/Ni catalyst due to the maintenance of Ni in the reduced state by the Rh 33) . Rh _ Ni bimetallic catalysts derived from HTlcs precursors were successfully tested in the autothermal reforming of CH4 in the presence of small amounts of ethane 34) . Rh , since Ni(II) can react with the anionic chelating agent of EDTA 4-, producing the highly stable species [Ni(EDTA)] 2-.…”

Section: Improvement Of Stability Of Ni/mg(al)o Catalysts By the Addimentioning

confidence: 99%

“…Rh , since Ni(II) can react with the anionic chelating agent of EDTA 4-, producing the highly stable species [Ni(EDTA)] 2-. We studied on the effects of the preparation methods of the precursors as follows: A) coprecipitation of Ni, Mg and Al nitrates with carbonate; B) co-precipitation of Mg and Al nitrates with presynthesized nickel chelate; and C) anion exchange of NO3 -of HT with nickel chelate 34) . Ni/Mg17(Al2)O catalyst prepared by method A was the most active for converting CH4, with a high H2 yield in the steam reforming of CH4, probably because method A provided the best distribution of the active phase.…”

Section: Improvement Of Stability Of Ni/mg(al)o Catalysts By the Addimentioning

confidence: 99%

“…Immersion of Mg(Al)O periclase in aqueous solution of metal chelates, reconstituted Mg _ Al HT was by the "memory effect" and the metal chelates were incorporated as anions in the surface HT structure. Rh, Ru and Pt were supported on Mg(Al)O by using noble metals prechelated with EDTA 4 , which were incorporated in the interlayer of Mg _ Al HT reconstituted by the "memory effect" 34) . The amount of noble metals could be reduced from 2.0 to 0.1 wt% of support without decreases in catalytic activity or selectivity for synthesis gas product in CO2 reforming of CH4 35) .…”

Section: Improvement Of Stability Of Ni/mg(al)o Catalysts By the Addimentioning

confidence: 99%

“…Rh, Ru and Pt were supported on Mg(Al)O by using noble metals prechelated with EDTA 4 , which were incorporated in the interlayer of Mg _ Al HT reconstituted by the "memory effect" 34) . The amount of noble metals could be reduced from 2.0 to 0.1 wt% of support without decreases in catalytic activity or selectivity for synthesis gas product in CO2 reforming of CH4 35) . The synthesis strategy applied for preparing noble metal catalysts supported on Mg(Al)O, is summarized in Scheme 3 14) .…”

Section: Improvement Of Stability Of Ni/mg(al)o Catalysts By the Addimentioning

confidence: 99%

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Preparation of Highly Dispersed Ni Catalysts for H<sub>2</sub> Production for Polymer Electrolyte Fuel Cells

Shishido

Takehira

2015

J. Jpn. Petrol. Inst.

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Reforming of methane and propane with supported Ni catalysts was investigated for the production of hydrogen for polymer electrolyte fuel cells (PEFCs). Supported Ni catalysts were prepared from Mg(Ni) _ Al hydrotalicitelike compounds (HTlcs) as the precursor. The precursors were prepared by the co-precipitation method from nitrates of the metal components, thermally decomposed, and then in-situ reduced to form supported Ni catalysts. Ni 2 can effectively replace the Mg 2 site in the HTlcs, resulting in the formation of highly dispersed and stable Ni metal particles on supported Ni catalysts. Supported Ni catalysts prepared by this method showed higher activity than catalysts prepared by the conventional impregnation method such as Ni/α-Al2O3 and Ni/MgO. Moreover, the activity and stability of supported Ni catalysts were improved by combining a small amount of noble metals by adopting the "memory effect," which allows the reconstitution of the original hydrotalcite-like structure, and were effective for the production of hydrogen under the daily start-up and shutd-own operations.

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A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

Huang

Wang

et al. 2012

Angewandte Chemie

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Storing hydrogen safely and efficiently is one of the major technological barriers preventing the widespread application of hydrogen-fueled cells, such as proton exchange membrane fuel cells (PEMFCs). Hydrous hydrazine (N 2 H 4 ·H 2 O) is considered as a promising liquid hydrogen storage material owing to the high content of hydrogen (7.9 %) and the advantage of CO-free H 2 produced.[1] In particular, hydrous hydrazine offers great potential as a hydrogen storage material for some special applications, such as unmanned space vehicles and submarine power sources, where hydrazine is usually used as a propellant.The decomposition of hydrazine proceeds by two typical reaction routes: [2] H 2 NNH 2 ! N 2 ðgÞ þ 2 H 2 ðgÞ ð 1Þ 3 H 2 NNH 2 ! 4 NH 3 ðgÞ þ N 2 ðgÞ ð 2ÞReaction (2) not only decreases the yield of H 2 but also complicates the separation process of products, because the ammonia by-product would poison the Nafion membrane and the fuel-cell catalysts. Thereby, it is of crucial importance to develop a highly selective catalyst over which the reaction proceeds only by pathway (1) at low temperatures. To this end, Xu and co-workers [3] synthesized a series of nickelcontaining bimetallic nanoparticles, including Ni-Rh, Ni-Pt, and Ni-Ir, which showed high H 2 selectivity at room temperature. Nevertheless, the incorporation of noble metals to nickel greatly increased the cost of catalysts. In a subsequent study by Xu and co-workers, [4] Ni-Fe nanoparticles were employed as catalysts for this reaction. However, the nanoparticles were only active at 70 8C, and addition of 0.5 mol L À1NaOH was necessary for the high selectivity. Moreover, the practical application of colloidal nanoparticles will raise significant problems, such as mass production, handling, stability, separation, and recyclability. Therefore, from the viewpoint of practical applications, a supported base metal catalyst is a preferred choice owing to its low cost, good mechanical stability, and easy separation from the reaction medium. Herein, using a Ni-Al hydrotalcite-like compound (Ni-Al-HT) as the precursor, we obtained a highly dispersed nickel catalyst that presented 100 % conversion of N 2 H 4 ·H 2 O and up to 93 % selectivity to H 2 for the decomposition of N 2 H 4 ·H 2 O at ambient temperature. To our knowledge, this is the first report in which supported base metal catalysts show such high selectivity towards the formation of H 2 .It is well-known that supported noble metal catalysts, especially iridium catalysts, are very active for the decomposition of hydrazine. Compared with Ir, Ni is less active. [5] Accordingly, to obtain a high activity over Ni catalysts, a very high loading of Ni is required while maintaining a high degree of dispersion. Hydrotalcite-like compounds have been demonstrated to be excellent precursors for the preparation of highly dispersed and high-loading metal catalysts.[6] Herein, we synthesized binary Ni-Al-HT with interlayer CO 3 2À anions by a co-precipitation method.[7] After reduction in a H 2 atmosphere at 50...

show abstract

Untitled

Cited by 113 publications

References 17 publications

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

Preparation of Highly Dispersed Ni Catalysts for H<sub>2</sub> Production for Polymer Electrolyte Fuel Cells

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

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Untitled

Cited by 113 publications

References 17 publications

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N2H4⋅H2O Decomposition

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N2H4⋅H2O Decomposition

Preparation of Highly Dispersed Ni Catalysts for H<sub>2</sub> Production for Polymer Electrolyte Fuel Cells

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N2H4⋅H2O Decomposition

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A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition

A Noble‐Metal‐Free Catalyst Derived from Ni‐Al Hydrotalcite for Hydrogen Generation from N₂H₄⋅H₂O Decomposition