Adsorption and Decomposition of H₂S on MgO(100), NiMgO(100), and ZnO(0001) Surfaces:  A First-Principles Density Functional Study

Abstract

The adsorption and dissociation of H2S on MgO(100), Ni-doped MgO(100), and ZnO(0001) was studied using first-principles density-functional calculations (DFT-GGA) and periodic supercells. The bonding of H2S and its S-containing dissociated species (HS and S) is substantially stronger on ZnO(0001) than on MgO(100), making dissociation easier on zinc oxide. This behavior can be explained by the smaller ionicity in ZnO, which leads to a larger electron density around the Zn atoms and a larger reactivity toward S-containing molecules. Replacing some of the metal centers of MgO(100) with Ni atoms enhances the binding of S-containing species through new electronic states associated with the Ni 3d levels and located above the occupied {O 2p + Mg 3s} bands. In addition, structural defects, like steps, expose metal centers with lower coordination and larger reactivity than pentacoordinated Mg atoms in MgO(100). A simple model based on perturbation theory and band−orbital mixing is able to explain the differences in the reactivity of MgO(100) and ZnO(0001) and the behavior of other oxides (Al2O3, Cr2O3, Cr3O4, Cu2O) in the presence of sulfur-containing molecules. The model predicts a negative correlation between the reactivity of the oxides and the size of the electronic band gap, with the chemical activity of an oxide depending mainly on how well its bands mix with the orbitals of H2S. The electrostatic interactions between the Madelung field of the oxide and the dipole moment of the molecule play only a secondary role in bonding.

Mechanism of Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide

“…Therefore, we can conclude that gaseous products of heterogeneous reaction of OCS over MgO include CO 2 , H 2 S, and SO 2 . Figure 6 shows the dynamic changes of in situ DRIFTS spectra for the MgO sample exposed to a flow of dry 1000 ppm of OCS/N 2 and then dry OCS/air at 303 K. The surface HS, which is formed from the dissociative adsorption of H 2 S on MgO, 38,39 was observable in dry nitrogen ( Figure 6A, spectra a-d), while it decreased quickly when O 2 was introduced into the feed gas ( Figure 6A, spectra e-h). We also observed the decrease of HS at 2578 cm -1 in intensity as a function of time in Figures 1 and 2.…”

Individual Gas Molecules Detection Using Zinc Oxide–Graphene Hybrid Nanosensor: A DFT Study

“…H 2 S prefers to dissociatively adsorb on the ZnO (1010) surface with an adsorption energy of −1.36 eV [88]. Moreover, the calculated E ad of H 2 S on the ZnO-graphene compound is higher than the values reported for its adsorption on the pristine graphene (−0.11 eV) [89], pristine ZnO (0001) (−0.91 eV) [90], and pristine hexagonal monolayer ZnO (−0.54 eV) [91] surfaces, proposing the great capability of the ZnO-graphene hybrid for H 2 S dissociation. The experimental reported data confirm our DFT findings.…”

Studies on Sono-Chemical Biodiesel Production Using Smoke Deposited Nano MgO Catalyst

“…Nano sized MgO, catalyses transesterification reaction as a basic heterogeneous catalyst. When Mg atoms located at corner or edge sites of MgO nano particles have a relatively low coordination number and a positive charge that is substantially smaller than that in the bulk [18,19]. These cations are expected to be the chemically active sites of the nanoparticles [20,21].…”