Quantum dynamics origin of high photocatalytic activity of mixed-phase anatase/rutile TiO2

Abstract

Mixed anatase/rutile TiO2 exhibits high photocatalytic activity; however, the mechanism underlying the high performance of the mixed phases is not fully understood. We have performed time-domain ab initio calculations to study the exited state dynamics in mixed phase TiO2 and to investigate the impact of an oxygen vacancy on the dynamics. The anatase(100)/rutile(001) heterostructures with and without an oxygen vacancy used in this work exhibit type II band alignment with the conduction band of rutile residing above that of anatase. The oxygen vacancy introduces a hole trap state inside the bandgap. Owing to a strong coupling between the donor and acceptor states, the electron and hole transfers across the anatase/rutile interface occur on an ultrafast 100 fs timescale in both systems. The decoupling of electron and hole favors a long-lived charge separated state. The electron–hole recombination across the pristine anatase/rutile interface takes 6.6 ns and is significantly slower than that in the pure anatase and rutile phases, showing good agreement with experiments. The electron transfer dynamics is independent of the oxygen vacancy, which has some influence on the hole transfer and a strong effect on carrier recombination. By creating a hole trap state, the vacancy accelerates carrier losses by over an order of magnitude. The fast charge separation and the long lifetime of the charge separated state rationalize the enhanced photocatalytic performance of mixed phase TiO2 compared to the pure phases.

CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO2(110) Surface

“…Our previous simulations using trajectories of similar length showed good results for a broad range of materials, including pristine and doped TiO 2 and TiO 2 sensitized with other semiconductors. 62 , 71 , 96 , 97 …”

Effect of diatomite addition on crystalline phase formation of TiO2 and photocatalytic degradation of MDMA

“…Recently, several theoretical [45] and experimental studies [42][43][44][45] showed that mixed phases (rutile/anatase) [50] and (anatase/brookite) [51] exhibit higher photocatalytic activity than pure anatase or rutile phase due to the interface rutile/anatase heterojunction which reduces the electron (e -)-hole(h + ) recombination [52]. Y. Wei [53] proved using ab initio calculation that the lifetime of charges separation (e -, h + ) in TiO2 mixed phase is longer than in pure rutile and anatase phases. It was also found that a ternary mixture of anatase, rutile and brookite phase inhibits the recombination of charges pairs by capturing the electrons [54][55].…”

Density Functional Theory Half-Electron Self-Energy Correction for Fast and Accurate Nonadiabatic Molecular Dynamics

“…38−40 The current NA-MD approach treats light and fast electrons quantum mechanically while describing the heavy and slow nuclei (semi)classically. This approach has been successfully applied to study photoexcitation charge dynamics in a broad range of systems, including metal oxides, 41 BP, 42 and other two-dimensional materials, 43 as well as metal halide perovskites. 44 The electronic structure calculations and AIMD were performed using Vienna ab initio Simulation Package (VASP).…”

“…The decoherence-induced surface hopping (DISH) algorithm and the classical path approximation were employed, , as implemented in the time-dependent Kohn–Sham DFT (TD-DFT). − Phase correction was applied to correct the arbitrary phase in the adiabatic wave functions, and the NAC was computed with the projector-augmented wave (PAW) potentials. − The current NA-MD approach treats light and fast electrons quantum mechanically while describing the heavy and slow nuclei (semi)­classically. This approach has been successfully applied to study photoexcitation charge dynamics in a broad range of systems, including metal oxides, BP, and other two-dimensional materials, as well as metal halide perovskites …”