Promoted hydrogen release from ammonia borane with mannitol via a solid-state reaction route

Area of Science:

• Materials Science
• Chemical Engineering
• Solid-State Chemistry

Background:

• Ammonia borane (NH(3)BH(3), AB) is a promising hydrogen storage material.
• Efficient hydrogen release from AB requires optimized dehydrogenation conditions.
• Undesired byproducts like borazine can complicate hydrogen purification.

Purpose of the Study:

• To investigate the effect of mannitol (C(6)H(8)(OH)(6), MA) as an additive on the hydrogen release from ammonia borane.
• To understand the reaction mechanism and identify factors influencing dehydrogenation.
• To evaluate the potential for improved hydrogen generation and purification.

Main Methods:

• Solid-state reaction experiments with varying MA/AB ratios.
• Temperature-programmed desorption (TPD) to analyze hydrogen release profiles.
• Spectroscopic analyses including Raman, Fourier transform infrared (FTIR), and (11)B nuclear magnetic resonance (NMR) spectroscopy.
• Use of anhydrous MgCl(2) for ammonia absorption.

Main Results:

• Mannitol additive significantly lowers the dehydrogenation temperature of ammonia borane by approximately 25 °C.
• The formation of borazine byproduct is suppressed in the presence of mannitol.
• Spectroscopic data confirm the breaking of B-N, B-H, and O-H bonds and the formation of B-O bonds, indicating a solid-state reaction mechanism.
• Anhydrous MgCl(2) effectively absorbs released ammonia, facilitating hydrogen purification.

Conclusions:

• Mannitol acts as an effective additive to promote solid-state hydrogen release from ammonia borane.
• The hydroxyl groups in mannitol play a crucial role in the enhanced dehydrogenation process.
• The observed reaction mechanism provides a pathway for efficient and cleaner hydrogen generation from ammonia borane.