Toward viable H2 storage in Ca decorated low-dimensional materials with insights from reference quantum Monte Carlo

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Hydrogen technology is vital for reducing CO2 emissions and pollution.
• Current hydrogen storage in carbon fiber tanks limits fuel economy in mobile applications.
• Efficient molecular hydrogen (H2) adsorption requires specific binding energies (-0.2 to -0.4 eV), which are difficult to achieve.

Purpose of the Study:

• To investigate novel strategies for enhancing H2 adsorption for efficient hydrogen storage.
• To overcome the limitations of calcium decorators on graphene, such as thermodynamic instability.
• To accurately predict H2 binding energies using advanced computational methods.

Main Methods:

• Utilized state-of-the-art fixed-node diffusion Monte Carlo (DMC) simulations.
• Employed various density functional approximations (DFAs).
• Investigated two anchoring strategies: Ca on boron-doped graphene and Ca inside carbon nanotubes.

Main Results:

• Confirmed stable anchoring of Ca on boron-doped graphene and within carbon nanotubes.
• Demonstrated that these anchoring strategies significantly boost H2 adsorption energy.
• Achieved viable H2 adsorption energy within a Ca-decorated carbon nanotube, suitable for storage.

Conclusions:

• Anchoring calcium atoms in specific nanostructures offers a promising route for efficient hydrogen storage.
• The developed computational benchmarks (DMC binding energies) will guide future materials design.
• This research paves the way for data-driven development of advanced hydrogen storage materials.