Local bonding and atomic environments in Ni-catalyzed complex hydrides.

Area of Science:

• Materials Science
• Catalysis
• Hydrogen Storage

Background:

• LiBH4/MgH2 and Li3BN2H8 are advanced materials for hydrogen storage.
• Nickel catalysts are employed to enhance hydrogen release kinetics.
• Understanding the catalyst's atomic environment is key to optimizing performance.

Purpose of the Study:

• To elucidate the local atomic structure and bonding of Ni catalysts in LiBH4/MgH2 and Li3BN2H8.
• To investigate the catalytic activity of Ni species for hydrogen chemisorption.

Main Methods:

• X-ray absorption spectroscopy (XAS) at the Ni K-edge.
• Ball milling for catalyst introduction and material processing.
• Density functional theory (DFT) surface calculations.

Main Results:

• XAS revealed Ni2+ reduction to Ni0, forming disordered nanoclusters with a local structure resembling Ni3B.
• Ni atoms were found coordinated by boron with specific interatomic distances.
• DFT calculations identified the Ni3B(100) surface as having the lowest kinetic barrier for H2 chemisorption.

Conclusions:

• The Ni catalyst exists as nanoclusters with a Ni3B-like local structure in the studied hydrogen storage materials.
• The Ni3B(100) surface demonstrates high potential for efficient hydrogen adsorption, relevant for catalysis in hydrogen storage applications.