title: Quasiparticle interfacial level alignment of highly hybridized frontier levels: H2O on TiO2(110).
abstract: Knowledge of the frontier levels' alignment prior to photoirradiation is necessary to achieve a complete quantitative description of H2O photocatalysis on TiO2(110). Although H2O on rutile TiO2(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H2O occupied levels is still lacking. For experiment, this is due to the H2O levels being obscured by hybridization with TiO2(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H2O-TiO2(110) interface. Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) G0W0, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H2O on TiO2(110). We perform this separation as a function of H2O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO2(110) surface, the H2O 3a1 and 1b1 levels are broadened into several peaks between 5 and 1 eV below the TiO2(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H2O adsorbed intact and dissociated on stoichiometric TiO2(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H2O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QPGW (scQPGW1) to obtain the ionization potential of the H2O-TiO2(110) interface.
authors.affiliation: ICN2 - Institut Català de Nanociència i Nanotecnologia, ICN2 Building, Campus UAB, E-08193 Bellaterra, Barcelona, Barcelona, Spain.|CSIC - Consejo Superior de Investigaciones Científicas, ICN2 Building, Campus UAB, E-08193 Bellaterra, Barcelona, Barcelona, Spain.
authors.forename: Annapaola
authors.initials: A
authors.lastname: Migani
authors.affiliation: Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Departamento de Física de Materiales, Universidad del País Vasco UPV/EHU and DIPC , E-20018 San Sebastián, Gipuzkoa, Spain.
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Mowbray
authors.affiliation: Department of Physics and ICQD/HFNL, University of Science and Technology of China , Hefei, Anhui 230026, China.|Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Hrvoje
authors.initials: H
authors.lastname: Petek