Generating mechanism of catalytic effect for hydrogen absorption/desorption reactions in NaAIH4–TiCl3

Kazutaka Ikeda, Fumika Fujisaki, Toshiya Otomo, Hidetoshi Ohshita, Takashi Honda, Toru Kawamata, Hiroshi Arima, Kazumasa Sugiyama, Hitoshi Abe, Hyunjeong Kim, Kouji Sakaki, Yumiko Nakamura, Akihiko Machida, Toyoto Sato, Shigeyuki Takagi, Shin Ichi Orimo

Research output: Contribution to journalArticlepeer-review

Abstract

The hydrogen desorption and absorption reactions of the complex metal hydride NaAlH4 are disproportionation processes, and the kinetics can be improved by adding a few mol% of Ti compounds, although the catalytic mechanism, including the location and state of Ti, remains unknown. In this study, we aimed to reveal the generating mechanism of catalytic Al–Ti alloy in NaAlH4 with TiCl3 using quantum multiprobe techniques such as neutron diffraction (ND), synchrotron X-ray diffraction (XRD), anomalous X-ray scattering (AXS), and X-ray absorption fine structure (XAFS). Rietveld refinements of the ND and XRD, profiles before the first desorption of NaAlD(H)4–0.02TiCl3 showed that Al in NaAlD(H)4 was partially substituted by Ti. On the other hand, Ti was not present in NaAlH4, and Al–Ti nanoparticles were detected in the XRD profile after the first re-absorption. This was consistent with the AXS and XAFS results. It is suggested that the substitution promotes the formation of a highly dispersed nanosized Al–Ti alloy during the first desorption process and that the effectiveness of TiCl3 as an additive can be attributed to the dispersion of Ti.

Original languageEnglish
Article number8349
JournalApplied Sciences (Switzerland)
Volume11
Issue number18
DOIs
Publication statusPublished - 2021 Sep

Keywords

  • Anomalous X-ray scattering
  • Hydride complex
  • Hydrogen storage
  • Neutron diffraction
  • X-ray absorption fine structure
  • X-ray diffraction

ASJC Scopus subject areas

  • Materials Science(all)
  • Instrumentation
  • Engineering(all)
  • Process Chemistry and Technology
  • Computer Science Applications
  • Fluid Flow and Transfer Processes

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