Operando spectroscopic analyses for the ammonia absorption process of sodium borohydride

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Ammonia borohydride is a promising material for chemical hydrogen storage.
• Understanding the ammonia absorption mechanism is crucial for optimizing storage capacity and release.
• Previous studies have explored ammonia storage but lacked in-situ characterization of the absorption process.

Purpose of the Study:

• To investigate the ammonia absorption process of sodium borohydride.
• To elucidate the chemical state changes of sodium borohydride and ammonia during absorption.
• To clarify the role of liquefaction in the ammonia storage mechanism.

Main Methods:

• Operando Nuclear Magnetic Resonance (NMR) spectroscopy was employed to monitor chemical states in real-time.
• Operando Fourier Transform Infrared (FT-IR) spectroscopy provided complementary information on molecular vibrations and bonding.
• Measurements were conducted under various ammonia pressures to simulate different storage conditions.

Main Results:

• Characteristic spectral variations in both sodium borohydride and ammonia were observed during the absorption process.
• Evidence of ammonia liquefaction within the sodium borohydride matrix was identified.
• The study successfully correlated spectral changes with the chemical transformations occurring during ammonia absorption.

Conclusions:

• The ammonia absorption process of sodium borohydride involves significant chemical state variations.
• Ammonia liquefaction plays a key role in the storage mechanism, influencing the material's properties.
• This research provides fundamental insights into sodium borohydride-based ammonia storage, paving the way for improved material design.