title: Ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store.
abstract: Industrially, the artificial fixation of atmospheric nitrogen to ammonia is carried out using the Haber-Bosch process, but this process requires high temperatures and pressures, and consumes more than 1% of the world's power production. Therefore the search is on for a more environmentally benign process that occurs under milder conditions. Here, we report that a Ru-loaded electride [Ca(24)Al(28)O(64)](4+)(e(-))(4) (Ru/C12A7:e(-)), which has high electron-donating power and chemical stability, works as an efficient catalyst for ammonia synthesis. Highly efficient ammonia synthesis is achieved with a catalytic activity that is an order of magnitude greater than those of other previously reported Ru-loaded catalysts and with almost half the reaction activation energy. Kinetic analysis with infrared spectroscopy reveals that C12A7:e(-) markedly enhances N(2) dissociation on Ru by the back donation of electrons and that the poisoning of ruthenium surfaces by hydrogen adatoms can be suppressed effectively because of the ability of C12A7:e(-) to store hydrogen reversibly.
authors.affiliation: Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama                 226-8503, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kitano
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Inoue
authors.forename: Youhei
authors.initials: Y
authors.lastname: Yamazaki
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Hayashi
authors.forename: Shinji
authors.initials: S
authors.lastname: Kanbara
authors.forename: Satoru
authors.initials: S
authors.lastname: Matsuishi
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Sung-Wng
authors.initials: SW
authors.lastname: Kim
authors.forename: Michikazu
authors.initials: M
authors.lastname: Hara
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono