The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Hideo Hosono - One of the best experts on this subject based on the ideXlab platform.
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Why Ca_2NH works as an efficient and stable support of Ru catalyst in Ammonia Synthesis
Research on Chemical Intermediates, 2021Co-Authors: Masaaki Kitano, Kyosuke Yamagata, Hideo HosonoAbstract:Hydride-based materials have recently attracted attention because of their significant promotion effect on transition metal catalysts in Ammonia Synthesis under mild conditions. Here, we clarify the effect of hydride-nitride, Ca_2NH, on the activity and stability of Ru catalyst as a catalyst support for Ammonia Synthesis. The anionic electrons formed at H^‒ ion vacancy sites in Ca_2NH effectively promote the N_2 dissociation over Ru surface, which accounts for the high catalytic performance with a low apparent activation energy. The catalytic activity of Ru/Ca_2NH is much superior to those of Ru/C12A7:e^‒, Ru/Sr_2NH, and Ru/CaNH. The simple metal hydride, CaH_2, with Ru exhibits higher catalytic performance than Ru/Ca_2NH, but its stability is poor because weak Ru-CaH_2 interaction causes aggregation of Ru nanoparticles during the reaction. On the other hand, Ru nanoparticles are anchored on Ca_2NH surface through a strong Ru–N interaction, which leads to excellent stability of Ru/Ca_2NH catalyst.
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air stable calcium cyanamide supported ruthenium catalyst for Ammonia Synthesis and decomposition
ACS Applied Energy Materials, 2020Co-Authors: Kazuhisa Kishida, Masaaki Kitano, Toshiharu Yokoyama, Peter V. Sushko, Masato Sasase, Yasuhiro Niwa, Kiya Ogasawara, Hideo HosonoAbstract:Efficient Ammonia Synthesis and decomposition processes under mild conditions are important to meet the expanding demand in major applications of Ammonia as the energy carrier and to provide feedst...
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Solid solution for catalytic Ammonia Synthesis from nitrogen and hydrogen gases at 50 °C
Nature Communications, 2020Co-Authors: Masashi Hattori, Hideo Hosono, Shinya Iijima, Takuya Nakao, Michikazu HaraAbstract:Ammonia Synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic Ammonia Synthesis at lower temperatures. The lack of efficient catalysts for Ammonia Synthesis from N_2 and H_2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for Ammonia production toward zero CO_2 emissions. Here, we report a new approach for low temperature Ammonia Synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF_2 and CaH_2 formed at low temperatures. The catalyst produced Ammonia from N_2 and H_2 gases at 50 °C with an extremely small activation energy of 20 kJ mol^−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca^2+ and H^− ions in the solid solution and the facile release of hydrogen atoms from H^− sites.
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Solid solution for catalytic Ammonia Synthesis from nitrogen and hydrogen gases at 50 °C.
Nature communications, 2020Co-Authors: Masashi Hattori, Hideo Hosono, Shinya Iijima, Takuya Nakao, Michikazu HaraAbstract:The lack of efficient catalysts for Ammonia Synthesis from N2 and H2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for Ammonia production toward zero CO2 emissions. Here, we report a new approach for low temperature Ammonia Synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF2 and CaH2 formed at low temperatures. The catalyst produced Ammonia from N2 and H2 gases at 50 °C with an extremely small activation energy of 20 kJ mol−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca2+ and H− ions in the solid solution and the facile release of hydrogen atoms from H− sites. Ammonia Synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic Ammonia Synthesis at lower temperatures.
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transition metal doped ru nanoparticles loaded on metal hydrides for efficient Ammonia Synthesis from first principles
Journal of Physical Chemistry C, 2020Co-Authors: Takuya Nakao, Tomofumi Tada, Hideo HosonoAbstract:Ru-loaded hydrides work as efficient catalysts for Ammonia Synthesis at low temperatures. The advantages of high activity when using Ru-loaded hydride catalysts are as follows: (i) electron injecti...
Masaaki Kitano - One of the best experts on this subject based on the ideXlab platform.
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Why Ca_2NH works as an efficient and stable support of Ru catalyst in Ammonia Synthesis
Research on Chemical Intermediates, 2021Co-Authors: Masaaki Kitano, Kyosuke Yamagata, Hideo HosonoAbstract:Hydride-based materials have recently attracted attention because of their significant promotion effect on transition metal catalysts in Ammonia Synthesis under mild conditions. Here, we clarify the effect of hydride-nitride, Ca_2NH, on the activity and stability of Ru catalyst as a catalyst support for Ammonia Synthesis. The anionic electrons formed at H^‒ ion vacancy sites in Ca_2NH effectively promote the N_2 dissociation over Ru surface, which accounts for the high catalytic performance with a low apparent activation energy. The catalytic activity of Ru/Ca_2NH is much superior to those of Ru/C12A7:e^‒, Ru/Sr_2NH, and Ru/CaNH. The simple metal hydride, CaH_2, with Ru exhibits higher catalytic performance than Ru/Ca_2NH, but its stability is poor because weak Ru-CaH_2 interaction causes aggregation of Ru nanoparticles during the reaction. On the other hand, Ru nanoparticles are anchored on Ca_2NH surface through a strong Ru–N interaction, which leads to excellent stability of Ru/Ca_2NH catalyst.
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air stable calcium cyanamide supported ruthenium catalyst for Ammonia Synthesis and decomposition
ACS Applied Energy Materials, 2020Co-Authors: Kazuhisa Kishida, Masaaki Kitano, Toshiharu Yokoyama, Peter V. Sushko, Masato Sasase, Yasuhiro Niwa, Kiya Ogasawara, Hideo HosonoAbstract:Efficient Ammonia Synthesis and decomposition processes under mild conditions are important to meet the expanding demand in major applications of Ammonia as the energy carrier and to provide feedst...
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self organized ruthenium barium core shell nanoparticles on a mesoporous calcium amide matrix for efficient low temperature Ammonia Synthesis
Angewandte Chemie, 2018Co-Authors: Masaaki Kitano, Yasunori Inoue, Toshiharu Yokoyama, Tomofumi Tada, Kazuhisa Kishida, Masato Sasase, Yasukazu Kobayashi, Kohei Nishiyama, Shigeki Kawamura, Michikazu HaraAbstract:A low-temperature Ammonia Synthesis process is required for on-site Synthesis. Barium-doped calcium amide (Ba-Ca(NH2 )2 ) enhances the efficacy of Ammonia Synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wustite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru-Ba core-shell structures are self-organized on the Ba-Ca(NH2 )2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g-1 ). These self-organized nanostructures account for the high catalytic performance in low-temperature Ammonia Synthesis.
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ru loaded c12a7 e electride as a catalyst for Ammonia Synthesis
ACS Catalysis, 2017Co-Authors: Michikazu Hara, Masaaki Kitano, Hideo HosonoAbstract:The artificial mass production of Ammonia has supported the increase in human population and modern civilization for over 100 years. However, more efficient Ammonia production is now a significant concern for society. Here we show that Ru-loaded C12A7:e– electride derived from 12CaO·7Al2O3 (C12A7:O2–) acts as an efficient and stable catalyst for Ammonia Synthesis. Ammonia Synthesis over Ru nanoparticles-loaded C12A7:e– (Ru/C12A7:e–) is distinct from other conventional catalysts in both mechanism and properties. The dissociative adsorption of N2 molecules, which is the largest energy barrier in Ammonia Synthesis for conventional catalysts, is no longer the rate-limiting step for the Ru/C12A7:e– catalyst. In addition, Ru on the electride prevents the inhibition of Ammonia Synthesis by hydrogen adatoms, known as hydrogen poisoning, which is a common and serious drawback of Ru catalysts. This characteristic results in the highly efficient formation of Ammonia over the Ru/C12A7:e– catalyst.
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Ammonia Synthesis over co mo alloy nanoparticle catalyst prepared via sodium naphthalenide driven reduction
Chemical Communications, 2016Co-Authors: Yuki Tsuji, Masaaki Kitano, Michikazu Hara, Toshiharu Yokoyama, Kazuhisa Kishida, Masato Sasase, Hideo HosonoAbstract:We report the Synthesis of Co–Mo alloy nanoparticles with a uniform distribution of the alloy elements on CeO2via sodium naphthalenide-driven reduction. The resulting sample functions as a highly efficient and stable catalyst for Ammonia Synthesis. Based on the metal weight, the catalytic activity is ca. 20 times higher than that of Co3Mo3N.
Michikazu Hara - One of the best experts on this subject based on the ideXlab platform.
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Solid solution for catalytic Ammonia Synthesis from nitrogen and hydrogen gases at 50 °C.
Nature communications, 2020Co-Authors: Masashi Hattori, Hideo Hosono, Shinya Iijima, Takuya Nakao, Michikazu HaraAbstract:The lack of efficient catalysts for Ammonia Synthesis from N2 and H2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for Ammonia production toward zero CO2 emissions. Here, we report a new approach for low temperature Ammonia Synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF2 and CaH2 formed at low temperatures. The catalyst produced Ammonia from N2 and H2 gases at 50 °C with an extremely small activation energy of 20 kJ mol−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca2+ and H− ions in the solid solution and the facile release of hydrogen atoms from H− sites. Ammonia Synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic Ammonia Synthesis at lower temperatures.
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Solid solution for catalytic Ammonia Synthesis from nitrogen and hydrogen gases at 50 °C
Nature Communications, 2020Co-Authors: Masashi Hattori, Hideo Hosono, Shinya Iijima, Takuya Nakao, Michikazu HaraAbstract:Ammonia Synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic Ammonia Synthesis at lower temperatures. The lack of efficient catalysts for Ammonia Synthesis from N_2 and H_2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for Ammonia production toward zero CO_2 emissions. Here, we report a new approach for low temperature Ammonia Synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF_2 and CaH_2 formed at low temperatures. The catalyst produced Ammonia from N_2 and H_2 gases at 50 °C with an extremely small activation energy of 20 kJ mol^−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca^2+ and H^− ions in the solid solution and the facile release of hydrogen atoms from H^− sites.
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self organized ruthenium barium core shell nanoparticles on a mesoporous calcium amide matrix for efficient low temperature Ammonia Synthesis
Angewandte Chemie, 2018Co-Authors: Masaaki Kitano, Yasunori Inoue, Toshiharu Yokoyama, Tomofumi Tada, Kazuhisa Kishida, Masato Sasase, Yasukazu Kobayashi, Kohei Nishiyama, Shigeki Kawamura, Michikazu HaraAbstract:A low-temperature Ammonia Synthesis process is required for on-site Synthesis. Barium-doped calcium amide (Ba-Ca(NH2 )2 ) enhances the efficacy of Ammonia Synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wustite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru-Ba core-shell structures are self-organized on the Ba-Ca(NH2 )2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g-1 ). These self-organized nanostructures account for the high catalytic performance in low-temperature Ammonia Synthesis.
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ru loaded c12a7 e electride as a catalyst for Ammonia Synthesis
ACS Catalysis, 2017Co-Authors: Michikazu Hara, Masaaki Kitano, Hideo HosonoAbstract:The artificial mass production of Ammonia has supported the increase in human population and modern civilization for over 100 years. However, more efficient Ammonia production is now a significant concern for society. Here we show that Ru-loaded C12A7:e– electride derived from 12CaO·7Al2O3 (C12A7:O2–) acts as an efficient and stable catalyst for Ammonia Synthesis. Ammonia Synthesis over Ru nanoparticles-loaded C12A7:e– (Ru/C12A7:e–) is distinct from other conventional catalysts in both mechanism and properties. The dissociative adsorption of N2 molecules, which is the largest energy barrier in Ammonia Synthesis for conventional catalysts, is no longer the rate-limiting step for the Ru/C12A7:e– catalyst. In addition, Ru on the electride prevents the inhibition of Ammonia Synthesis by hydrogen adatoms, known as hydrogen poisoning, which is a common and serious drawback of Ru catalysts. This characteristic results in the highly efficient formation of Ammonia over the Ru/C12A7:e– catalyst.
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Ammonia Synthesis over co mo alloy nanoparticle catalyst prepared via sodium naphthalenide driven reduction
Chemical Communications, 2016Co-Authors: Yuki Tsuji, Masaaki Kitano, Michikazu Hara, Toshiharu Yokoyama, Kazuhisa Kishida, Masato Sasase, Hideo HosonoAbstract:We report the Synthesis of Co–Mo alloy nanoparticles with a uniform distribution of the alloy elements on CeO2via sodium naphthalenide-driven reduction. The resulting sample functions as a highly efficient and stable catalyst for Ammonia Synthesis. Based on the metal weight, the catalytic activity is ca. 20 times higher than that of Co3Mo3N.
Toshiharu Yokoyama - One of the best experts on this subject based on the ideXlab platform.
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air stable calcium cyanamide supported ruthenium catalyst for Ammonia Synthesis and decomposition
ACS Applied Energy Materials, 2020Co-Authors: Kazuhisa Kishida, Masaaki Kitano, Toshiharu Yokoyama, Peter V. Sushko, Masato Sasase, Yasuhiro Niwa, Kiya Ogasawara, Hideo HosonoAbstract:Efficient Ammonia Synthesis and decomposition processes under mild conditions are important to meet the expanding demand in major applications of Ammonia as the energy carrier and to provide feedst...
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self organized ruthenium barium core shell nanoparticles on a mesoporous calcium amide matrix for efficient low temperature Ammonia Synthesis
Angewandte Chemie, 2018Co-Authors: Masaaki Kitano, Yasunori Inoue, Toshiharu Yokoyama, Tomofumi Tada, Kazuhisa Kishida, Masato Sasase, Yasukazu Kobayashi, Kohei Nishiyama, Shigeki Kawamura, Michikazu HaraAbstract:A low-temperature Ammonia Synthesis process is required for on-site Synthesis. Barium-doped calcium amide (Ba-Ca(NH2 )2 ) enhances the efficacy of Ammonia Synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wustite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru-Ba core-shell structures are self-organized on the Ba-Ca(NH2 )2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g-1 ). These self-organized nanostructures account for the high catalytic performance in low-temperature Ammonia Synthesis.
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Ammonia Synthesis over co mo alloy nanoparticle catalyst prepared via sodium naphthalenide driven reduction
Chemical Communications, 2016Co-Authors: Yuki Tsuji, Masaaki Kitano, Michikazu Hara, Toshiharu Yokoyama, Kazuhisa Kishida, Masato Sasase, Hideo HosonoAbstract:We report the Synthesis of Co–Mo alloy nanoparticles with a uniform distribution of the alloy elements on CeO2via sodium naphthalenide-driven reduction. The resulting sample functions as a highly efficient and stable catalyst for Ammonia Synthesis. Based on the metal weight, the catalytic activity is ca. 20 times higher than that of Co3Mo3N.
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essential role of hydride ion in ruthenium based Ammonia Synthesis catalysts
Chemical Science, 2016Co-Authors: Masaaki Kitano, Michikazu Hara, Yasunori Inoue, Satoru Matsuishi, Toshiharu Yokoyama, Takuya Nakao, Tomofumi Tada, Hiroki Ishikawa, Kyosuke Yamagata, Hideo HosonoAbstract:The efficient reduction of atmospheric nitrogen to Ammonia under low pressure and temperature conditions has been a challenge in meeting the rapidly increasing demand for fertilizers and hydrogen storage. Here, we report that Ca2N:e−, a two-dimensional electride, combined with ruthenium nanoparticles (Ru/Ca2N:e−) exhibits efficient and stable catalytic activity down to 200 °C. This catalytic performance is due to [Ca2N]+·e1−x−Hx− formed by a reversible reaction of an anionic electron with hydrogen (Ca2N:e− + xH ↔ [Ca2N]+·e1−x−Hx−) during Ammonia Synthesis. The simplest hydride, CaH2, with Ru also exhibits catalytic performance comparable to Ru/Ca2N:e−. The resultant electrons in these hydrides have a low work function of 2.3 eV, which facilitates the cleavage of N2 molecules. The smooth reversible exchangeability between anionic electrons and H− ions in hydrides at low temperatures suppresses hydrogen poisoning of the Ru surfaces. The present work demonstrates the high potential of metal hydrides as efficient promoters for low-temperature Ammonia Synthesis.
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water durable electride y5si3 electronic structure and catalytic activity for Ammonia Synthesis
Journal of the American Chemical Society, 2016Co-Authors: Yangfan Lu, Masaaki Kitano, Toshiharu Yokoyama, Jiang Li, Tomofumi Tada, Yoshitake Toda, Shigenori Ueda, Hideo HosonoAbstract:We report an air and water stable electride Y5Si3 and its catalytic activity for direct Ammonia Synthesis. It crystallizes in the Mn5Si3-type structure and confines 0.79/f.u. anionic electrons in the quasi-one-dimensional holes. These anionic electrons strongly hybridize with yttrium 4d electrons, giving rise to improved chemical stability. The Ammonia Synthesis rate using Ru(7.8 wt %)-loaded Y5Si3 was as high as 1.9 mmol/g/h under 0.1 MPa and at 400 °C with activation energy of ∼50 kJ/mol. Its strong electron-donating ability to Ru metal of Y5Si3 is considered to enhance nitrogen dissociation and reduce the activation energy of Ammonia Synthesis reaction. Catalytic activity was not suppressed even after Y5Si3, once dipped into water, was used as the catalyst promoter. These findings provide novel insights into the design of simple catalysts for Ammonia Synthesis.
Yasunori Inoue - One of the best experts on this subject based on the ideXlab platform.
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self organized ruthenium barium core shell nanoparticles on a mesoporous calcium amide matrix for efficient low temperature Ammonia Synthesis
Angewandte Chemie, 2018Co-Authors: Masaaki Kitano, Yasunori Inoue, Toshiharu Yokoyama, Tomofumi Tada, Kazuhisa Kishida, Masato Sasase, Yasukazu Kobayashi, Kohei Nishiyama, Shigeki Kawamura, Michikazu HaraAbstract:A low-temperature Ammonia Synthesis process is required for on-site Synthesis. Barium-doped calcium amide (Ba-Ca(NH2 )2 ) enhances the efficacy of Ammonia Synthesis mediated by Ru and Co by 2 orders of magnitude more than that of a conventional Ru catalyst at temperatures below 300 °C. Furthermore, the presented catalysts are superior to the wustite-based Fe catalyst, which is known as a highly active industrial catalyst at low temperatures and pressures. Nanosized Ru-Ba core-shell structures are self-organized on the Ba-Ca(NH2 )2 support during H2 pretreatment, and the support material is simultaneously converted into a mesoporous structure with a high surface area (>100 m2 g-1 ). These self-organized nanostructures account for the high catalytic performance in low-temperature Ammonia Synthesis.
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essential role of hydride ion in ruthenium based Ammonia Synthesis catalysts
Chemical Science, 2016Co-Authors: Masaaki Kitano, Michikazu Hara, Yasunori Inoue, Satoru Matsuishi, Toshiharu Yokoyama, Takuya Nakao, Tomofumi Tada, Hiroki Ishikawa, Kyosuke Yamagata, Hideo HosonoAbstract:The efficient reduction of atmospheric nitrogen to Ammonia under low pressure and temperature conditions has been a challenge in meeting the rapidly increasing demand for fertilizers and hydrogen storage. Here, we report that Ca2N:e−, a two-dimensional electride, combined with ruthenium nanoparticles (Ru/Ca2N:e−) exhibits efficient and stable catalytic activity down to 200 °C. This catalytic performance is due to [Ca2N]+·e1−x−Hx− formed by a reversible reaction of an anionic electron with hydrogen (Ca2N:e− + xH ↔ [Ca2N]+·e1−x−Hx−) during Ammonia Synthesis. The simplest hydride, CaH2, with Ru also exhibits catalytic performance comparable to Ru/Ca2N:e−. The resultant electrons in these hydrides have a low work function of 2.3 eV, which facilitates the cleavage of N2 molecules. The smooth reversible exchangeability between anionic electrons and H− ions in hydrides at low temperatures suppresses hydrogen poisoning of the Ru surfaces. The present work demonstrates the high potential of metal hydrides as efficient promoters for low-temperature Ammonia Synthesis.
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mechanism switching of Ammonia Synthesis over ru loaded electride catalyst at metal insulator transition
Journal of the American Chemical Society, 2015Co-Authors: Shinji Kanbara, Masaaki Kitano, Michikazu Hara, Yasunori Inoue, Toshiharu Yokoyama, Hideo HosonoAbstract:The substitution of electrons for O2– anions in the crystallographic cages of [Ca24Al28O64]4+(O2–)2 was investigated to clarify the correlation between the electronic properties and catalytic activity for Ammonia Synthesis in Ru-loaded [Ca24Al28O64]4+(O2–)2–x(e–)2x (0 ≤ x ≤ 2). This catalyst has low catalytic performance with an electron concentration (Ne) lower than 1 × 1021 cm–3 and a high apparent activation energy (Ea) for Ammonia Synthesis comparable to that for conventional Ru-based catalysts with a basic promoter such as alkali or alkaline earth compounds. Replacement of more than half of the cage O2– anions with electrons (Ne ≈ 1 × 1021 cm–3) significantly changes the reaction mechanism to yield a catalytic activity that is an order higher and with half the Ea. The metal–insulator transition of [Ca24Al28O64]4+(O2–)2–x(e–)2x also occurs at Ne ≈ 1 × 1021 cm–3 and is triggered by structural relaxation of the crystallographic cage induced by the replacement of O2– anions with electrons. These observat...
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Electride support boosts nitrogen dissociation over ruthenium catalyst and shifts the bottleneck in Ammonia Synthesis
Nature Communications, 2015Co-Authors: Masaaki Kitano, Michikazu Hara, Yasunori Inoue, Shinji Kanbara, Toshiharu Yokoyama, Navaratnarajah Kuganathan, Peter V. Sushko, Hideo HosonoAbstract:Development of catalysts that enhance dissociation of the nitrogen–nitrogen triple bond will reduce costs of Ammonia production. Here, the authors study Ammonia Synthesis over a ruthenium loaded electride catalyst and show that the rate-determining step is shifted to nitrogen–hydrogen bond formation. Novel approaches to efficient Ammonia Synthesis at an ambient pressure are actively sought out so as to reduce the cost of Ammonia production and to allow for compact production facilities. It is accepted that the key is the development of a high-performance catalyst that significantly enhances dissociation of the nitrogen–nitrogen triple bond, which is generally considered a rate-determining step. Here we examine kinetics of nitrogen and hydrogen isotope exchange and hydrogen adsorption/desorption reactions for a recently discovered efficient catalyst for Ammonia Synthesis—ruthenium-loaded 12CaO·7Al_2O_3 electride (Ru/C12A7:e^−)—and find that the rate controlling step of Ammonia Synthesis over Ru/C12A7:e^− is not dissociation of the nitrogen–nitrogen triple bond but the subsequent formation of N–H_ n species. A mechanism of Ammonia Synthesis involving reversible storage and release of hydrogen atoms on the Ru/C12A7:e^− surface is proposed on the basis of observed hydrogen absorption/desorption kinetics.
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electride support boosts nitrogen dissociation over ruthenium catalyst and shifts the bottleneck in Ammonia Synthesis
Nature Communications, 2015Co-Authors: Masaaki Kitano, Michikazu Hara, Yasunori Inoue, Shinji Kanbara, Toshiharu Yokoyama, Navaratnarajah Kuganathan, Peter V. Sushko, Hideo HosonoAbstract:Novel approaches to efficient Ammonia Synthesis at an ambient pressure are actively sought out so as to reduce the cost of Ammonia production and to allow for compact production facilities. It is accepted that the key is the development of a high-performance catalyst that significantly enhances dissociation of the nitrogen-nitrogen triple bond, which is generally considered a rate-determining step. Here we examine kinetics of nitrogen and hydrogen isotope exchange and hydrogen adsorption/desorption reactions for a recently discovered efficient catalyst for Ammonia Synthesis--ruthenium-loaded 12CaO·7Al2O3 electride (Ru/C12A7:e(-))--and find that the rate controlling step of Ammonia Synthesis over Ru/C12A7:e(-) is not dissociation of the nitrogen-nitrogen triple bond but the subsequent formation of N-Hn species. A mechanism of Ammonia Synthesis involving reversible storage and release of hydrogen atoms on the Ru/C12A7:e(-) surface is proposed on the basis of observed hydrogen absorption/desorption kinetics.