Quantum chemical study of the adsorption of water on zinc oxide surface

CO2 and CO Capture on the ZnO Surface: A GCMC and Electronic Structure Study

The amount of polluting gases released into the atmosphere has grown drastically. Among them, it is possible to cite the release of CO2 and CO gases on a large scale as one of the products of the complete and incomplete combustion of petroleum-derived fuels. It is worth noting that the production of energy by burning fossil fuels supplies the energy demand but causes environmental damage, and several studies have addressed the reduction. One of them is using materials with the potential to capture these gases. The experimental and theoretical studies have significant contributions that promote advances in this area. Among the materials investigated, ZnO has emerged, demonstrating the considerable potential for capturing various gases, including CO2 and CO. This work used density functional theory (DFT) and Grand Canonical Monte Carlo Method (GCMC) to investigate the adsorption of CO2 and CO on the surface of Zinc oxide (ZnO) to obtain adsorption isotherms and interaction energy and the interaction nature. The results suggest that CO2 adsorption slightly changed the angle of the O-C-O to values less than 180°. For the CO, its carbon atom interacts simultaneously with Zn and O of the ZnO surface. However, CO interactions have an ionic character with a lower binding energy value than the CO2 interaction. The energies calculated using the PM6 and DFT methods generated results compatible with the experimental values. In applications involving a mixture of these two gases, the adsorption of CO2 should be favored, and there may be inhibition of the adsorption of CO for high CO2 concentrations.

Effect of porous zinc–biochar nanocomposites on Cr(vi) adsorption from aqueous solution

A new synthesis method was developed to produce zinc–biochar nanocomposites from sugarcane bagasse.

Mechanisms of and Effect of Coadsorption on Water Dissociation on an Oxygen Vacancy of the MgO(100) Surface

The dissociation mechanism of a water molecule at an oxygen vacancy on the MgO(100) surface was studied by using the embedded cluster method at the DFT/B3 LYP level, while the energetic information was refined by using the IMOMO method at the CCSD level. We found that a water molecule initially adsorbs on one of the magnesium ions surrounding the vacancy site with a binding energy of 15.98 kcal mol(-1). It then can dissociate on the MgO(100) surface along two possible dissociation pathways. One pathway produces a hydroxyl group bonded to the original magnesium with a proton filling the vacancy via a transition state with a barrier of 4.67 kcal mol(-1) relative to the adsorbed water configuration. The other pathway yields two hydroxy groups; the hydroxy group originally belonging to the water molecule fills the vacancy, while the hydrogen atom binds with the surface oxygen to form the other hydroxy group. Hydrogen atoms of these hydroxy groups can recombine to form a hydrogen molecule and the surface is healed. Although the barrier (14.09 kcal mol(-1)) of the rate-controlling step of the latter pathway is higher than that of the former one, the energies of all of its stationary points are lower than that of the separated reactants (H(2)O+cluster). The effects of water coadsorption are modeled by placing an additional water molecule near the active center, which suggests that the more coadsorbed water molecules further stabilize the hydroxy species and prevent the hydrogen molecule formation through the latter pathway. The results support the photoemission spectral evidence of water dissociation on the defective MgO(100) surface at low water coverage.