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Mechanistic study of hydrazine decomposition on Ir(111)

Lu, Xiuyuan, Francis, Samantha, Motta, Davide, Dimitratos, Nikolaos and Roldan, Alberto 2020. Mechanistic study of hydrazine decomposition on Ir(111). Physical Chemistry Chemical Physics 22 (7) , pp. 3883-3896. 10.1039/C9CP06525C
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Abstract

Hydrogen transport and storage technology remain one of the critical challenges of the hydrogen economy. Hydrazine (N2H4) is a carbon-free hydrogen carrier which has been widely used as fuel in the field of space exploration. We have combined experiments and computer simulations in order to gain a better understanding of the N2H4 decomposition on Ir catalyst, the most efficient catalyst for hydrazine decomposition up to date. We have identified metallic Ir rather than IrO2 as the active phase for hydrazine decomposition and carried out density functional theory (DFT) calculations to systematically investigate the changes in the electronic structure along with the catalytic decomposition mechanisms. Three catalytic mechanisms to hydrazine decomposition over Ir(111) have been found: (i) intramolecular reaction between hydrazine molecules, (ii) intramolecular reaction between co-adsorbed amino groups, and (iii) hydrazine dehydrogenation assisted by co-adsorbed amino groups. These mechanisms follow five different pathways for which transition states and intermediates have been identified. The results show that hydrazine decomposition on Ir(111) starts preferentially with an initial N-N bond scission followed by hydrazine dehydrogenation assisted by the amino produced, eventually leading to ammonia and nitrogen production. The preference for N-N scission mechanisms was rationalized by analyzing the electronic structure. This analysis showed that upon hydrazine adsorption, the π bond between nitrogen atoms becomes weaker.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: Royal Society of Chemistry
ISSN: 1463-9076
Funders: EPSRC
Date of First Compliant Deposit: 13 February 2020
Date of Acceptance: 31 January 2020
Last Modified: 10 Mar 2020 22:29
URI: http://orca.cf.ac.uk/id/eprint/129635

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