Kinetic Control of Oxygen Interstitial Interaction with TiO₂(110) via the Surface Fermi Energy

Atomically clean surfaces of semiconducting oxides efficiently mediate the interconversion of gas-phase O2 and solid-phase oxygen interstitial atoms (Oi). First-principles calculations together with mesoscale microkinetic modeling are employed for TiO2(110) to determine reaction pathways, assess appropriate rate expressions, and obtain corresponding activation energies and pre-exponential factors. The Fermi energy (EF) at the surface influences the rate-determining step for both injection and annihilation of Oi. The barriers range between 0.72–0.82 eV for injection and 0.60–2.34 eV for annihilation and may be manipulated through intentional control of EF. At equilibrium, the microkinetic model and first-principles calculations indicate that interconversion of Oi species in the first and second sublayers limits the rate. The effective pre-exponential factors for injection and annihilation are surprisingly low, probably resulting from the use of simple Langmuir-like rate expressions to describe a complicated kinetic sequence.