Dynamics of the Photogenerated Hole at the Rutile TiO₂(110)/Water Interface: A Nonadiabatic Simulation Study

Abstract

Hydrogen production in photoelectrochemical cells constitutes an important avenue toward carbon-free fuel. The most convenient process for hydrogen production is the splitting of water molecules, which necessitates a catalytic reaction involving a semiconductor. Here, we introduce a framework for the study of photocatalyzed reactions on semiconductor surfaces based on time-dependent density functional theory that explicitly accounts for the evolution of electronically excited states. Within this framework, we investigate the possibility of hole-mediated splitting of molecularly adsorbed water on a representative metal oxide surfacethe rutile TiO 2 (110). We find that oxidative dehydrogenation of water is possible in synergy with thermal effects at temperatures between 60 and 100 K only when defects like Ti interstitials are present in the subsurface region. This study presents a general computational strategy for describing photoexcited semiconductor/adsorbate interfaces and also demonstrates that the occurrence of water dissociation on the rutile TiO 2 (110) surface depends sensitively on the local atomic environment and external parameters such as temperature.

Mechanism of photocatalytic water oxidation on small TiO2 nanoparticles

“…Recent Ehrenfest NAMD simulations of periodic TiO 2 surfaces also considered this mechanism, 25 but the simulation times were too short (up to 20 fs) to be conclusive. Nakato and coworkers suggested that nucleophilic attack of water on a O br , activated by h + , might initiate the OER, 26 , 27 O br (h + ) + H 2 O(l) → ·O br OH + H + , generating a surface-bound hydroperoxyl radical.…”

Polaron-induced phonon localization and stiffening in rutile TiO2

“…Brillouin zone was sampled at Γ-point, except for smaller supercells used in convergence tests where we used Monkhorst-Pack k-point grids starting from 8 × 8 × 12 for a single unit cell. As in the works prior to this [3,25,31], we used PBE+U functional with U = 4.2 eV in all our calculations. In this study we used standard SIESTA pseudopotentials and SZP basis set.…”

Real-Time TD-DFT with Classical Ion Dynamics: Methodology and Applications

“…The number of layers was chosen based on earlier convergence studies. 83 The dangling bonds at the bottom of the slab are passivated with hydrogen atoms. The total number of atoms in the simulation cell is 197; during the dynamics, the bottom of the slab (48 atoms) is kept fixed with the interatomic distances equal to the corresponding bulk values.…”

“…This is a typical value for titania and has been confirmed previously in convergence studies. 20, 83 We use a DZP basis set and a collinear spin-polarized setup, and we sample the Brillouin zone by the Γ point.…”