論文

本文へのリンクあり
2021年11月5日

Barium oxide encapsulating cobalt nanoparticles supported on magnesium oxide: Active non-noble metal catalysts for ammonia synthesis under mild reaction conditions

ACS Catalysis
  • Katsutoshi Sato
  • Katsutoshi Nagaoka
  • Shin Ichiro Miyahara
  • Kotoko Tsujimaru
  • Yuichiro Wada
  • Takaaki Toriyama
  • Tomokazu Yamamoto
  • Syo Matsumura
  • Koji Inazu
  • Hirono Mohri
  • Takeshi Iwasa
  • Tetsuya Taketsugu
  • 全て表示

11
21
開始ページ
13050
終了ページ
13061
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1021/acscatal.1c02887
出版者・発行元
AMER CHEMICAL SOC

To realize a carbon-free society, catalysts are needed for the synthesis of ammonia under mild reaction conditions (<400 °C, <10 MPa) that use hydrogen produced from renewable energy. Ru-based catalysts are currently the most promising candidates; however, Ru is expensive and of low abundance. Here, we discovered that the encapsulation of Co nanoparticles with BaO enhanced the ammonia synthesis activity of Co and that a simple Ba-doped Co/MgO catalyst prereduced at an unusually high temperature of 700 °C (Co@BaO/MgO-700red) showed outstanding ammonia synthesis activity. The ammonia synthesis rate (24.6 mmol gcat−1 h−1) and turnover frequency (0.246 s−1) of the catalyst at 350 °C and 1.0 MPa were about 80 and 250 times higher, respectively, than those of the nondoped parent catalyst. At the same temperature but higher pressure (3.0 MPa), the ammonia synthesis rate was increased to 48.4 mmol gcat−1 h−1, which is higher than that of active Ru-based catalysts. In addition, at 1.0 MPa, our catalyst produced ammonia even at temperatures as low as 150 °C. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy investigations revealed that after reduction at 700 °C, the Co nanoparticles had become encapsulated by a nanofraction of BaO. The mechanism underlying the formation of this unique structure was considered to comprise reduction of oxidic Co to metallic Co, decomposition of BaCO3 to BaO, and migration of BaO and Co nanoparticles. Spectroscopic and density functional theory investigations revealed that adsorption of N2 on the Co atoms at the catalyst surface weakened the N2 triple bond to the strength of a double bond due to electron donation from Ba2+ of BaO via adjacent Co atoms; this weakening accelerated the cleavage of the triple bond, which is the rate-determining step for ammonia synthesis.

リンク情報
DOI
https://doi.org/10.1021/acscatal.1c02887
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000716773800021&DestApp=WOS_CPL
Scopus
https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85118140754&origin=inward 本文へのリンクあり
Scopus Citedby
https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85118140754&origin=inward
ID情報
  • DOI : 10.1021/acscatal.1c02887
  • ISSN : 2155-5435
  • eISSN : 2155-5435
  • SCOPUS ID : 85118140754
  • Web of Science ID : WOS:000716773800021

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