Dynamical pathways for the interaction of O2, H2O, CH4, and CO2 with a-alumina surfaces: Density functional tight-binding calculations

TL;DR

This study uses density functional tight-binding calculations and molecular dynamics to explore how O2, H2O, CH4, and CO2 molecules interact with alpha-alumina surfaces, revealing binding pathways, adsorption sites, and electronic effects.

Contribution

It provides new detailed insights into the physisorption mechanisms and binding pathways of key molecules on alumina surfaces using advanced computational methods.

Findings

O2 bonds primarily to Al atoms with high adsorbance.

CH4 dissociates into CH2+H2 with low adsorption rates.

Adsorption sites vary between Al-terminated and O-terminated surfaces.

Abstract

In this study, we investigated the physisorption mechanisms of O2, H2O, CH4, and CO2 molecules on alumina and their effect on electronic properties. We employed quantum-classical molecular dynamics simulations and the self-consistent-charge density-functional tight-binding (SCC-DFTB) approach to dynamically model these mechanisms. Our results revealed 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. We examined several adsorption sites and molecular orientations relative to Al-terminated and Ox-terminated alumina surfaces and 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 resulted 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. Our findings provide important insights into the physisorption mechanisms of molecules on alumina and their impact on electronic properties