title: Thermal decomposition of sodium amide, NaNH2, and sodium amide hydroxide composites, NaNH2-NaOH.
abstract: Sodium amide, NaNH2, has recently been shown to be a useful catalyst to decompose NH3into H2and N2, however, sodium hydroxide is omnipresent and commercially available NaNH2usually contains impurities of NaOH (<2%). The thermal decomposition of NaNH2and NaNH2-NaOH composites is systematically investigated and discussed. NaNH2is partially dissolved in NaOH at T > 100 °C, forming a non-stoichiometric solid solution of Na(OH)1-x(NH2)x(0 < x < ∼0.30), which crystallizes in an orthorhombic unit cell with the space group P212121determined by synchrotron powder X-ray diffraction. The composite xNaNH2-(1 - x)NaOH (∼0.70 < x < 0.72) shows a lowered melting point, ∼160 °C, compared to 200 and 318 °C for neat NaNH2and NaOH, respectively. We report that 0.36 mol of NH3per mol of NaNH2is released below 400 °C during heating in an argon atmosphere, initiated at its melting point, T = 200 °C, possibly due to the formation of the mixed sodium amide imide solid solution. Furthermore, NaOH reacts with NaNH2at elevated temperatures and provides the release of additional NH3.
authors.affiliation: Center for Materials Crystallography, Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark. trj@chem.au.dk and Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus C, Denmark.
authors.forename: Lars H
authors.initials: LH
authors.lastname: Jepsen
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, P. R. China.
authors.forename: Peikun
authors.initials: P
authors.lastname: Wang
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, P. R. China.
authors.forename: Guotao
authors.initials: G
authors.lastname: Wu
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, P. R. China.
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Xiong
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, P. R. China.
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.affiliation: Center for Materials Crystallography, Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark. trj@chem.au.dk.
authors.forename: Torben R
authors.identifier: http://orcid.org/0000-0002-4278-3221
authors.initials: TR
authors.lastname: Jensen