Comparing Quasiparticle H2O Level Alignment on Anatase and Rutile TiO2

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• 作者：Huijuan Sun ; Duncan J. Mowbray ; Annapaola Migani ; Jin Zhao ; Hrvoje Petek ; Angel Rubio
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：4242-4254
• 全文大小：912K
• ISSN：2155-5435

文摘

Knowledge of the alignment of molecular frontier levels in the ground state can be used to predict the photocatalytic activity of an interface. The position of the adsorbate鈥檚 highest occupied molecular orbital (HOMO) levels relative to the substrate鈥檚 valence band maximum (VBM) in the interface describes the favorability of photogenerated hole transfer from the VBM to the adsorbed molecule. This is a key quantity for assessing and comparing H₂O photooxidation activities on two prototypical photocatalytic TiO₂ surfaces: anatase (A)-TiO₂(101) and rutile (R)-TiO₂(110). Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) G₀W₀ calculations, we assess the relative photocatalytic activity of intact and dissociated H₂O on coordinately unsaturated (Ti_cus) sites of idealized stoichiometric A-TiO₂(101)/R-TiO₂(110) and bridging O vacancies (O_br^vac) of defective A-TiO_2鈥?i>x(101)/R-TiO_2鈥?i>x(110) surfaces (x = ¹/₄, ¹/₈) for various coverages. Such a many-body treatment is necessary to correctly describe the anisotropic screening of electron鈥揺lectron interactions at a photocatalytic interface and, hence, obtain accurate interfacial level alignments. The more favorable ground state HOMO level alignment for A-TiO₂(101) may explain why the anatase polymorph shows higher photocatalytic activities than the rutile polymorph. Our results indicate that (1) hole trapping is more favored on A-TiO₂(101) than R-TiO₂(110) and (2) HO@Ti_cus is more photocatalytically active than intact H₂O@Ti_cus.