Hydrogen Arrangements on Defective Quasi-Molecular BN Fragments.

Abstract

Considering the ever-increasing interest in metal-free materials, some potential chemical applications of quasi-molecular boron nitride (BN) derivatives were tested. Specifically, the behavior of BN fragments was analyzed when given defects, producing local electron density changes, were introduced by using topological engineering approaches. The inserted structural faults were Schottky-like divacancy (BN-d) defects, assembled in the fragment frame by the subtraction of one pair of B and N atoms or Stone–Wales (SW) defects. This study is aimed at highlighting the role of these important classes of defects in BN materials hypothesizing their future use in H2-based processes, related to either (i) H2 activation or (ii) H2 production, from preadsorbed hydrogenated molecular species on BN sites. Here, it has been observed that BN species, embodying SW defects, are characterized by endothermic H2 adsorption and fragmentation phenomena in order to guess their potential use in processes based on the transformation or production of hydrogen. On the contrary, in the presence of BN-d defects, and for reasons strictly related to local structural changes occurring along with the hydrogen rearrangements on the defective BN fragments, a possible use can be inferred. Precautions must be however taken to decrease the material rigidity that could actually decrease the ability of the BN fragment to flatten. This conversely seems to be a necessary requirement to have strong exothermic effects, following the rearrangements of the H2 molecules.