Surface interaction of H2O and H2S onto Ca12O12 nanocluster: Quantum-chemical analyses

To find the selectivity of H2S, we explicate the adsorption properties of water (H2O) and hydrogen sulfide (H2S) molecules on the external surfaces of free Ca12O12 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 Ca12O12 nanocages. Our theoretical findings indicate that although H2O seems to be adsorbed in molecular form, the H2S 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 1.87eV upon H2S 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 H2S-Ca12O12 complex are higher than those for the free nanocage. Our results suggest that Ca12O12 nanoclusters show promise in the adsorption/dissociation of H2S molecules, which can be used further for designing its selective sensor.