Supported ammonia borane decomposition through enhanced homopolar B-B coupling.

Area of Science:

• Materials Science
• Chemical Engineering
• Catalysis

Background:

• Thermolytic decomposition of ammonia borane (AB) releases hydrogen but generates impurities like ammonia, diborane, and borazine.
• Purification of the hydrogen stream is crucial for practical applications, necessitating effective by-product removal strategies.

Purpose of the Study:

• To investigate the efficacy of aluminum phosphate (AP) as a support material for ammonia borane (AB) thermolytic decomposition.
• To assess the impact of AP on hydrogen release temperature and by-product formation.
• To elucidate the mechanism of by-product suppression in supported AB decomposition.

Main Methods:

• In situ mass spectrometry (MS) to monitor gas evolution and reaction temperature.
• 11B MAS NMR spectroscopy to analyze the decomposition mechanism.
• Thermogravimetric analysis (TGA) and kinetic studies to evaluate decomposition efficiency.

Main Results:

• The optimal AB to AP (w/w) loading ratio of (1 × 4) minimized the dehydrogenation peak temperature by 18.89 °C.
• Ammonia by-product formation was reduced by 70.3% in the presence of AP.
• Borazine and diborane release were completely suppressed, and hydrogen release via B-B bonding was more efficient than B-N interaction.

Conclusions:

• Aluminum phosphate is a cost-effective and easily synthesized material for enhancing ammonia borane decomposition.
• AP significantly improves hydrogen purity by suppressing undesirable by-products.
• The study elucidates a mechanism involving intermolecular homopolar B-B bonding for efficient hydrogen release.