Essential role of hydride ion in ruthenium-based ammonia synthesis catalysts. Issue 7 (18th May 2016)

• Record Type: Journal Article
• Authors: Kitano, Masaaki; Inoue, Yasunori; Ishikawa, Hiroki; Yamagata, Kyosuke; Nakao, Takuya; Tada, Tomofumi; Matsuishi, Satoru; Yokoyama, Toshiharu; Hara, Michikazu; Hosono, Hideo
• Is Part Of: Chemical science. Volume 7:Issue 7(2016:Jul.)
• Page Start: 4036
• Page End: 4043
• Publication Date: 2016-05-18
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6sc00767h
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Ruthenium-loaded metal hydrides with hydrogen vacancies function as efficient catalysts for ammonia synthesis under low temperature and low pressure conditions. Abstract : 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 Ca2 N:e −, a two-dimensional electride, combined with ruthenium nanoparticles (Ru/Ca2 N:e − ) exhibits efficient and stable catalytic activity down to 200 °C. This catalytic performance is due to [Ca2 N] + ·e1− x − H x − formed by a reversible reaction of an anionic electron with hydrogen (Ca2 N:e − + x H ↔ [Ca2 N] + ·e1− x − H x − ) during ammonia synthesis. The simplest hydride, CaH2, with Ru also exhibits catalytic performance comparable to Ru/Ca2 N: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.