Hydrogen adsorption on borophene surfaces decorated with transition metal atoms

Abstract

Borophene allotropes β12, χ3, and 2-Pmmn are studied with periodic DFT and finite atom centered basis sets. The hypothetical buckled 2-Pmmn allotrope is stabilized via a natural appearance of hexagonal vacancies. Fe, Ni and Co are bound strongest to the borophene surfaces when comparing to Cu, alkali metals (Li, Na and K) and Zn. DFT functional choice is not deterministic for interaction energies, basis set superposition error (BSSE) significantly affects the energetics for pob-TZVP results. A single hydrogen molecule is stabilized with Kubas interaction on Ni-decorated systems. Additional H2 molecules are stabilized via end-on interactions preferably at the borophene vacancies. The H2 interaction energy is found to be –5 kJ mol-1 for the finite B36 system when BSSE and dispersion corrections are used. This value is confirmed by the DPLNO-CCSD(T) calculations. Pristine β12 and χ3 allotropes, when considering the hollow sites only, confirm a hydrogen storage gravimetric density of 7 and 8.5 wt%, respectively.

Keywords: Borophene, Gaussian Basis Set, hydrogen storage, Periodic DFT Calculations, Transition Metals