Solid-state synthesis of LiBD(4) observed by in situ neutron diffraction.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Chemistry

Background:

• The synthesis of lithium borohydride (Li[(11)BD(4)]) is crucial for applications in hydrogen storage and as a chemical reductant.
• Previous synthesis routes from pure elements required significantly higher temperatures, suggesting a substantial activation barrier.

Purpose of the Study:

• To investigate the synthesis pathway of Li[(11)BD(4)] from lithium boride (LiB) and deuterium (D(2)) under high pressure.
• To determine the reaction kinetics and thermodynamics, particularly the onset temperature for Li[(11)BD(4)] formation.

Main Methods:

• In situ neutron diffraction was employed to monitor the reaction progress in real-time.
• High pressure (180 bar) and controlled temperature ramps (up to 773 K) were utilized.

Main Results:

• The formation of Li[(11)BD(4)] was observed at temperatures significantly lower than previously reported.
• The reaction initiates with the decomposition of LiB into LiD, followed by Li[(11)BD(4)] formation starting at 623 K.
• Complete conversion was not achieved within the experimental temperature range, with residual LiD remaining.

Conclusions:

• The binary compound LiB facilitates lower-temperature synthesis of Li[(11)BD(4)] due to atomic-level intermixing and a less rigid boron lattice.
• The reaction proceeds through an intermediate LiD phase.
• Further optimization of temperature and reaction time may be necessary for complete Li[(11)BD(4)] synthesis.