Interlayer Hydrogen Recombination from Hydrogen Boride Nanosheets Elucidated by Isotope Labeling

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Borophane, a 2D boron material, has shown promise in various applications.
• Understanding hydrogen release mechanisms from boride materials is crucial for their practical use.
• Isotopic substitution offers a powerful tool to study reaction pathways.

Purpose of the Study:

• To synthesize deuterium boride (DB) nanosheets via ion exchange.
• To investigate the isotopic effects in DB using spectroscopy.
• To elucidate the hydrogen release mechanism from hydrogen boride (HB) and DB nanosheets using temperature-programmed desorption (TPD).

Main Methods:

• Synthesis of deuterium boride (DB) nanosheets through ion exchange of magnesium diboride with deuterons.
• Fourier-transform infrared (FTIR) spectroscopy to analyze chemical bonds and isotopic effects.
• Temperature-programmed desorption (TPD) coupled with mass spectrometry to study gas release upon heating.
• Controlled mixing of DB and hydrogen boride (HB) nanosheets with graphene to study reaction kinetics.

Main Results:

• Successful synthesis of DB nanosheets with observable B-H stretching vibrational mode shifts in FTIR spectra, confirming deuteration.
• TPD analysis showed a significantly higher hydrogen-deuterium (HD) signal than H2 and D2 from mixed DB and HB samples.
• This indicates that hydrogen release from HB nanosheets is predominantly from interlayer recombination.
• TPD studies with graphene confirmed interlayer hydrogen recombination is dominant below 623 K, while intralayer recombination occurs at higher temperatures (>623 K) after hydrogen migration.

Conclusions:

• Deuterium boride (DB) nanosheets were successfully synthesized, exhibiting clear isotopic effects.
• The study demonstrates that hydrogen release from hydrogen boride (HB) nanosheets primarily occurs through interlayer recombination at lower temperatures.
• Intralayer hydrogen recombination becomes significant at higher temperatures, facilitated by hydrogen migration on the nanosheet surfaces.