Quantum Chemical Prediction of Reaction Pathways and Rate Constants for the Reactions of O_<i>x</i> (<i>x</i> = 1 and 2) with Pristine and Defective Graphite (0001) Surfaces

We present reaction pathways for adsorption reactions of the O atom and O₂ molecule in the pristine and monovacancy defective graphite (0001) based on quantum chemical potential energy surfaces (PESs) obtained by the dispersion-augmented density-functional tight-binding (DFTB-D) method. We use a dicircumcoronene C₉₆H₂₄ (<b>L0D</b>) graphene slab as the pristine graphite (0001) model and dicircumcoronene C₉₅H₂₄ (<b>LIV</b>) as the graphite (0001) monovacancy defect model. We found that the adsorption reactions of O and O₂ on the <b>L0D</b> surface can produce defects on the graphite surface. O can yield CO, while O₂ can yield both CO and CO₂ molecules. The adsorption reactions of the O and O₂ on the <b>LIV</b> surface can produce a 2-C defective graphite surface and CO, and CO and CO₂, respectively. The O and O₂ more readily oxidize the defected surface, <b>LIV</b>, than the defect-free surface, <b>L0D</b>. On the basis of the computed reaction pathways, we predict reaction rate constants in the temperature range between 300 and 3000 K using Rice–Ramsperger–Kassel–Marcus (RRKM) theory. High-temperature quantum chemical molecular dynamics simulations at 3000 K based on on-the-fly DFTB-D energies and gradients support the results of our PES studies