Dynamical Pathways for the Interaction of O2, H2O, CH4, and CO2 with α-Alumina Surfaces: Density-Functional Tight-Binding Calculations

Herein, the physisorption mechanisms of O2, H2O, CH4, and CO2 molecules on alumina and their effect on electronic properties are investigated. Quantum-classical molecular dynamics simulations and the self-consistent-charge density-functional tight-binding approach are used to dynamically model these mechanisms. Herein, the binding pathways of O, H, and C atoms in the various molecules to Al and O atoms at the top atomic layers of the alpha-alumina surface are revealed by the results. Several adsorption sites and molecular orientations relative to Al-terminated and Ox-terminated alumina surfaces are examined and it is found that the most stable physisorbed state on the Al-terminated surface is located above the Al atom, while the Ox-terminated state is found above the oxygen, resulting in enhanced optical adsorbance. The dissociation of CH4 into CH2+H2 after interaction with the surface results in hydrogen production, but with low adsorbate rates, while O2 molecules primarily bond to the Al atoms, leading to the highest adsorbance rate among the other molecules. Herein, important insights are provided by the findings into the physisorption mechanisms of molecules on alumina and their impact on electronic properties.