Molecular Dynamics Approach to the Physical Mixture of In2O3 and ZrO2: Defect Formation and Ionic Diffusion.

Recent research on the use of physical mixtures In2O3-ZrO2 has raised interesting questions as to how their combination enhances catalytic activity and selectivity. Specifically, the relationship between oxygen diffusion and defect formation and the epitaxial tension in the mixture should be further investigated. In this study, we aim to clarify some of these relationships through a molecular dynamics approach. Various potentials for the two oxides are compared and selected to describe the physical mixture of In2O3 and ZrO2. Different configurations of each single crystal and their physical mixture are simulated, and oxygen defect formation and diffusion are measured and compared. Significant oxygen defect formation is found in both crystals. In2O3 seems to be stabilized by the mixture, while ZrO2 is destabilized. Similar results were found for the ZrO2 doping with In and ln2O3 doping with Zr. The results explain the high activity and selectivity catalyst activity of the mixture for the production of isobutylene from ethanol.

Zn-doping and oxygen vacancy effects on the reactivity and properties of monoclinic and tetragonal ZrO2: a DFT study.

Zirconia oxide (ZrO2) is a material that has aroused great interest in the scientific community for its general use in various technological applications, such as fuel cells, solar cells, electronic devices, catalysis, dental biomaterial and ceramics. When it is applied as a catalyst, the doping and vacancy effects of their crystalline phases are important properties to guide new developments. This work investigates tetragonal and monoclinic crystalline phases of the Zn-doped ZrO2 by periodic density functional calculations. Changes in the electronic and acid-basic properties were performed by Bader charge analysis, the density of states calculations (DOS) and the projected density of states (PDOS). The formation of oxygen vacancies was also evaluated. The calculated oxygen vacancy formation energies indicate that it is much easier to generate oxygen vacancy in the Zn-doped ZrO2 than in the pure material; in addition, oxygen vacancy formation is favored in the monoclinic phase. Bader charge analyses and projected density of states indicated that the doping of ZrO2 with Zn creates more basic and acid sites. The most stable material is the Zn-doped 3-fold coordinated Zr atom of the m-ZrO2, which can be used for future developments and applications.