Long range corrected-wPBE based analysis of the H2O adsorption on magnetic BC3 nanosheets

Abstract

Density functional theory based methods were used for the analysis of the interaction between BC₃ (a graphene nanosheet doped with boron), pristine and with point defects (vacancies of carbon – V_C and boron – V_B), and the H₂O molecule. The Perdew–Burke–Ernzerhof (LC-wPBE) functional, which includes long range corrections, combined with the 6-31G(d) basis sets developed by Pople et al. was used. The results from the structural and electronic relaxation indicate that the BC₃ nanosheets, pristine and with V_C and V_B defects, present magnetic properties. For the neutral case, they have magnetic moments of 2, 4, and 3 bohr magnetons (μ_B). Roughly, BC₃ and BC₃/V_B present metallic character but BC₃/V_C exhibits semiconductor behavior. Adsorption of the H₂O molecule on the pristine BC₃ and BC₃/V_C nanolayers is mainly governed by van der Waals forces, yielding adsorption energies of −0.45 and −0.21 eV, respectively. In the BC₃–H₂O and BC₃/V_B–H₂O systems, the water molecule is oriented in a parallel manner to the BC₃ mesh, presenting equilibrium distances of 1.79 and 2.45 Å, respectively. This type of functionalization may produce changes in the hybridization of such bi-dimensional structures. Remarkably, in the BC₃/V_C–H₂O system, the water molecule is dissociated into hydroxyl and hydrogen moieties. Structural stability is achieved in the three systems (as was confirmed by vibrational analysis) and the magnetic properties are also preserved, or even enhanced. On BC₃–H₂O (pristine, and with V_C and V_B vacancies), the following was found: an increase in the polarity, low chemical reactivity and low values for the work function. Thus, BC₃–H₂O, BC₃/V_C–H₂O and BC₃/V_B–H₂O may be used for the transportation of pharmaceuticals, in optoelectronics and in the design of magnetic devices.