Development of a nuclear magnetic resonance system for in situ analysis of hydrogen storage materials under high pressures and temperatures

A NMR system for in situ analysis of hydrogen storage materials under high pressure and temperature conditions was developed. The system consists of a gas pressure and flow rate controlling unit, a temperature controller, a high temperature NMR probe tunable for both H1 and other nuclei, and a sample tube holder. Sample temperature can be controlled up to 623 K by heated N₂ gas flow. Sample tube atmosphere can be substituted by either H₂ or Ar and can be pressurized up to 1 MPa under constant flow rate up to 100 ml/min. During the NMR measurement, the pressure can be adjusted easily by just handle a back pressure valve. On the blank NMR measurement, ¹H background noise was confirmed to be very low. ¹H and ¹¹B NMR spectrum of LiBH₄ were successfully observed at high temperature for the demonstration of the system. The intensity of the ¹H NMR spectra of H₂ gas was also confirmed to be proportional to the applied pressure.