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Comparing quasiparticle H2O level alignment on anatase and rutile TiO2

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Rubio,  Angel
Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Departamento de Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, E-20018 San Sebastián, Spain;
Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

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Citation

Sun, H., Mowbray, D. J., Migani, A., Zhao, J., Petek, H., & Rubio, A. (2015). Comparing quasiparticle H2O level alignment on anatase and rutile TiO2. ACS Catalysis, 5(7), 4242-4254. doi:10.1021/acscatal.5b00529.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0027-7902-E
Abstract
Knowledge of the molecular frontier levels' alignment in the ground state can be used to predict the photocatalytic activity of an interface. The position of the adsorbate's highest occupied molecular orbital (HOMO) levels relative to the substrate's 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 (Ticus) sites of idealized stoichiometric A-TiO2(101)/R-TiO2(110) and bridging O vacancies (Obrvac) of defective A-TiO2-x(101)/R-TiO2-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-electron 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@Ticus is more photocatalytically active than intact H2O@Ticus.