Ab Initio Molecular Dynamics calculations on NO oxidation over oxygen functionalized Highly Oriented Pyrolytic Graphite

TL;DR

This study uses ab initio molecular dynamics to investigate NO oxidation on oxygen-functionalized graphite, revealing that NO$_2$ formation occurs at room temperature and providing detailed insights into reaction dynamics and product distributions.

Contribution

First AIMD study of NO oxidation on epoxy-functionalized graphite, showing reaction feasibility at low energies and elucidating structural and energetic factors influencing the process.

Findings

NO$_2$ forms at collision energies as low as 0.025 eV.

Scattered NO loses half of its translational energy.

Reactions occur under dynamic conditions with specific structural requirements.

Abstract

The oxidation of NO molecules on epoxy-functionalized highly oriented pyrolytic graphite, thermalized at 300 K, was studied by means of ab initio molecular dynamics (AIMD) calculations. Four collision energies and two different orientations were analyzed where the reaction, adsorption, and scattering probabilities were computed. Our results reveal that NO$_2$ formation can occur even at the lowest collision energy investigated (0.025 eV), approximately equivalent to room temperature (300 K), which agrees qualitatively with the experimental results. This underscores the influence of dynamics on the NO oxidation process, since this oxidation barrier was previously theoretically estimated to be about 0.1 eV at 0 K, which is four times higher than our lowest collision energy. Additionally, we obtained angular and energy distributions of the products under selected simulation conditions. Scattered NO molecules show low specular reflection, lose half of their initial translational energy, and remain vibrationally cold with minimal rotational excitation. Furthermore, a statistical analysis of all reactive trajectories, focusing on configurations at specific reaction moments, elucidated the structural requirements for the reaction to occur under dynamic conditions. Finally, this study demonstrates the potential of oxygen-doped carbon surfaces for the conversion of NO to NO$_2$.