Langmuir, Vol.36, No.42, 12632-12648, 2020
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 O-2 and solid-phase oxygen interstitial atoms (O-i). 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 preexponential factors. The Fermi energy (E-F) at the surface influences the rate-determining step for both injection and annihilation of O-i. 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 E-F. At equilibrium, the microkinetic model and first-principles calculations indicate that interconversion of O-i 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.