Surface interaction of H ₂ O and H ₂ S onto Ca ₁₂ O ₁₂ nanocluster: Quantum‐chemical analyses

Abstract

To find the selectivity of H 2 S, we explicate the adsorption properties of water (H 2 O) and hydrogen sulfide (H 2 S) molecules on the external surfaces of free Ca 12 O 12 nanocages using the density functional theory method. More specifically, binding energies, natural bond orbital charge transfer, dipole moment, molecular electrostatic potential, frontier molecular orbitals, density of states, and global indices of activities are calculated to deeply understand the impacts of the aforementioned molecules on the electronic and chemical properties of Ca 12 O 12 nanocages. Our theoretical findings indicate that although H 2 O seems to be adsorbed in molecular form, the H 2 S molecule is fully dissociated during the adsorption process because of the weak bond between sulfur and hydrogen atoms of the molecule. Interestingly, the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap of the nanocage is decreased by 1.87 eV upon H 2 S adsorption, indicating that the electrical conductivity of the nanocage is strongly increased by the dissociation process. In addition, the values of softness and electrophilicity for the H 2 S‐Ca 12 O 12 complex are higher than those for the free nanocage. Our results suggest that Ca 12 O 12 nanoclusters show promise in the adsorption/dissociation of H 2 S molecules, which can be used further for designing its selective sensor.