title: The effect of Sr(OH)2on the hydrogen storage properties of the Mg(NH2)2-2LiH system.
abstract: The doping effect of Sr(OH)2on the Mg(NH2)2-2LiH system is investigated considering different amounts of added Sr(OH)2in the range of 0.05 to 0.2 mol. Experimental results show that both the thermodynamic and the kinetic properties of Mg(NH2)2-2LiH are influenced by the presence of Sr(OH)2. The addition of 0.1 mol Sr(OH)2leads to a decrease in both the dehydrogenation onset and peak temperatures of ca. 70 and 13 °C, respectively, and an acceleration in the de/re-hydrogenation rates of one time at 150 °C compared to Mg(NH2)2-2LiH alone. Based on differential scanning calorimetry (DSC) analysis, the overall reaction enthalpy of the 0.1 Sr(OH)2-doped sample is calculated to be 44 kJ per mol-H2and there are two absorption events occurring in the doped sample instead of one in the pristine sample. For the applied experimental conditions, according to the in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Fourier Transform Infrared spectroscopy (FT-IR) analysis, the reaction mechanism has been finally defined: Sr(OH)2, Mg(NH2)2and LiH react with each other to form SrO, MgO and LiNH2during ball milling. After heating, SrO interacts with Mg(NH2)2producing MgO and Sr(NH2)2. Then Mg(NH2)2, LiNH2and Sr(NH2)2react with LiH to produce Li2NH, SrNH, Li2Mg(NH)2and Li2Mg2(NH)3in traces. After re-hydrogenation, LiSrH3, LiH and LiNH2are formed along with amorphous Mg(NH2)2. The reasons for the improved kinetics are: (a) during dehydrogenation, the in situ formation of SrNH appears to increase the interfacial contacts between Mg(NH2)2and LiH and also weakens the N-H bond of Mg(NH2)2; (b) during absorption, the formation of LiSrH3at around 150 °C could be the key factor for improving the hydrogenation properties.
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Hujun
authors.identifier: http://orcid.org/0000-0001-5464-6649
authors.initials: H
authors.lastname: Cao
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Han
authors.initials: H
authors.lastname: Wang
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Claudio
authors.initials: C
authors.lastname: Pistidda
authors.affiliation: Pavia H2 Lab, Department of Chemistry, Physical Chemistry Section, University of Pavia, Viale Taramelli 16, I-27100 Pavia, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Milanese
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Weijin
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Anna-Lisa
authors.initials: AL
authors.lastname: Chaudhary
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Antonio
authors.identifier: http://orcid.org/0000-0003-2619-7481
authors.initials: A
authors.lastname: Santoru
authors.affiliation: Department of Chemistry and Pharmacy, INSTM, Via Vienna 2, I-07100 Sassari, Italy.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Garroni
authors.affiliation: Deutsches Elektronen-Synchrotron a Research Centre of the Helmholtz Association, Notkestraße 85, Germany.
authors.forename: Jozef
authors.initials: J
authors.lastname: Bednarcik
authors.affiliation: Deutsches Elektronen-Synchrotron a Research Centre of the Helmholtz Association, Notkestraße 85, Germany.
authors.forename: Hanns-Peter
authors.initials: HP
authors.lastname: Liermann
authors.affiliation: Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Klassen
authors.affiliation: Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht GmbH, Max-Planck-Straße 1, D-21502 Geesthacht, Germany. hujun.cao@hzg.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Dornheim