Ab-initio study of hydrogen mobility in the vicinity of MgH

Radojka Vujasin, Jasmina Grbović Novaković, Nikola Novaković, Simone Giusepponi, Massimo Celino

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Abstract

Doping of MgH2with transition metals and their oxides is well-known procedure to improve its hydrogen (de)sorption properties, namely to lower the temperature of desorption and to achieve the kinetics speedup. In order to assess the influence Ti and TiO2doping has on H mobility and to characterize structurally and electronically observed differences, MgH2[sbnd]Mg interface doped with both Ti and TiO2have been studied using ab-initio interface molecular dynamics and bulk calculations. Results suggest different mechanisms of MgH2structure destabilization. The presence of dopants significantly stabilize MgH2[sbnd]Mg interface, which is confirmed by work of adhesion computation. Calculated formation energies show that interface system with doped TiO2is more stable. In terms of H mobility, molecular dynamics simulations confirm that Ti doping is more effective than TiO2in lowering the desorption temperature. The mobility of hydrogen atoms close to dopant is much higher in the case of Ti than in the case of TiO2. Electronic structure characterization reveals that oxygen atoms with high electron affinity forms more pronounced ionic bonding with Ti and the other neighbor Mg atoms. This in turn cause a shorter Ti[sbnd]H bonds in first coordination than in the case of Ti doping and further reduction of H atoms mobility. This is in accordance with molecular dynamics predictions.
Original languageEnglish
Pages (from-to)548 - 559
Number of pages12
JournalJournal of Alloys and Compounds
Volume696
DOIs
Publication statusPublished - 2017

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All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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