Theoretical study of adsorption of sodium, lithium, magnesium and calcium chloride and sulfate salts by pure and Sc-doped B12N12 nanocages and pure boron nitride nanosheet

Abstract

High concentrations of water-soluble chloride and sulfate salts may cause adverse effects to humans and plants. Boron nitride (BN) nanostructures seem able to remove these water-soluble salts. In addition, Li+, Mg2+, Ca2+, and Na2+ interactions with BN nanostructures have received much attention in fabricating high-performance metal-ion batteries. Accordingly, this study investigated the adsorption of chloride and sulfate salts of Li, Mg, Ca, and Na on pristine and scandium (Sc)-doped B12N12 nanocages and pure BN nanosheet through DFT calculations. Optimizing the structures at the B3LYP/6-31 g (d, p) and M062X/6-311 g (d, p) computational levels indicated very exothermic chemisorption of chloride and sulfate salts on the pure and Sc-doped B12N12 nanocages. The B12N12-LiCl and Sc@B11N12-LiCl complexes showed the highest negative adsorption energies of −26.33 and −57.30 kcal/mol among the chloride salts. The B12N12-MgSO4 and Sc@B12N12-MgSO4 complexes showed the highest adsorption energies of −69.27 and −102.70 kcal/mol among the sulfate salts. Studying the effect of the adsorption process on the electronic properties of the B12N12 nanocage showed a reduction in the energy gap upon the adsorption of all salts on the pure B12N12 nanocage with the lowest energy gap of 3.98 eV for B12N12-MgSO4. The adsorption energies of the individual salts and their complexes on the B12N12 nanosheet at the B3LYP/6-311 g (d, p) level imply the occurrence of physisorption. A significant reduction was observed in the energy gap by adsorbing the salts on the BN nanosheet. Adsorbing CaSO4 and MgSO4 on the BN nanosheet caused the largest variation of 1.71 and 1.56 eV in the energy gap, respectively. The promising results of our study highlight the potential application of BN nanostructures in the removal of various soluble salts and the fabrication of metal-ion batteries.