The unoccupied electronic structure of surface adsorbates
EMSL Project ID
13894a
Abstract
I. Solvated electron at surfaces and interfacesOur study based on 2PP and DFT of H2O/CH3OH on TiO2 rutile (110) surface shows that the interfacial solvated electron is very important intermediate in the electron transfer between a metal oxide/aqueous interface. The relaxation of solvated electron may involve the proton coupled electron transfer, which is likely to play an essential role in the photo-catalytic reactions.
Each metal oxide surface provides a unique template of acidic and basic sites for the adsorption of H2O. In order to understand how different environments can affect the interfacial electron solvation electron, we propose to study the electronic structure and dynamics of solvated electron at anatase H2O/TiO2(101) surface.
In contrast to solvated electron in liquid or in H2O bilayers on metal surfaces, at the metal oxide surface the solvated electron state shows up as an excited state. In our previous investigations, we characterized the wet electron states mainly by DFT and the Δ-SCF approximation. However, the DFT is a ground state theory and Δ-SCF is the first approximation to the excited state. It is still challenging and necessary to model the charge transfer properties of the solvated electron state on metal oxide surface with a higher-level theory such as TDDFT. We propose to investigate this state using TDDFT with cluster model for rutile and anatase and compare the results with the Δ-SCF method.
II. Correlation between geometric and electronic structure of defects on metal oxide surfaces
Our experimental-theoretical investigation of the O atom vacancy defect on TiO2(110) surface shows that the excess electrons are delocalized over several Ti atoms instead of being localized at the defect. In contrast to the pure DFT, however, hybrid DFT (B3LYP) and DFT+U methods lead to an unphysical symmetry broken structure. This asymmetric structure leads to a localized electron distribution with a distinct asymmetry for the defect states, which contradict the well-known positive bias STM images of the unoccupied states.
The B3LYP and DFT+U are two popular methods for correcting the self-interaction errors in pure DFT. In the investigation of impurity in SiO2 and defects in CeO2, DFT+U and B3LYP also lead to an asymmetric structure. By contrast to TiO2, however, the theoretical results are in good agreement with experiments.
We propose to study the defect states in different oxides with high-level ab-initio methods using a small cluster model and to compare the results with the pure and hybrid DFT methods.
III. Electronic structure of molecules chemisorbed on metal surface
We plan perform a combination of WPP with DFT. The Hamiltonian used to describe the motion of the electron is written as , in which Ve-Surf is the model potential for the clean surface, including the image potential. Ve-Ads is the adatom-induced potential given by: Ve-Ads=VPP+ΔVXC+VH(Δn) and VPP is the pseudopotential of the adsorbate. ΔVXC and VH(Δn) are the adsorbate induced exchange-correlation and Hartree potentials, which we will get from DFT. Based on this method, we will investigate the image potential state and how the image potential affects the molecular state on the metal surface.
Project Details
Project type
Exploratory Research
Start Date
2007-04-19
End Date
2008-04-20
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Feng M, J Zhao, and H Petek. 2008. "Atomlike, Hollow-Core-Bound Molecular Orbitals of C60." Science 320(5874):359-362. doi:10.1126/science.1155866
Feng M, J Zhao, T Huang, X Zhu, and H Petek. 2011. "The Electronic Properties of Superatom States of Hollow Molecules." Accounts of Chemical Research 44(5):360-368. doi:10.1021/ar1001445
Feng M, J Zhao, T Huang, X Zhu, and H Petek. 2011. "The Electronic Properties of Superatom States of Hollow Molecules." Accounts of Chemical Research 44(5):360-368. doi:10.1021/ar1001445
Huang T, J Zhao, M Feng, H Petek, S Yang, and L Dunsch. 2010. "Superatom orbitals of Sc?N@C?? and their intermolecular hybridization on Cu(110)-(2x1)-O surface." Physical Review. B, Condensed Matter and Materials Physics 81(8):085434. doi:10.1103/PhysRevB.81.085434
Hu S, J Zhao, Y Jin, J Yang, H Petek, and JG Hou. 2010. "Nearly Free Electron Superatom States of Carbon and Boron Nitride Nanotubes." Nano Letters 10(12):4830-4838. doi:10.1021/nl1023854
Jin Zhao, Jinlong Yang and Hrvoje Petek. 2009. "Theoretical study of the molecular and electronic structure of methanol on a TiO2(110) surface." Phys. Rev. B 80(23):235416. DOI:10.1103/PhysRevB.80.235416
Published 12/10/2009.
Jin Zhao, Min Feng, Jinlong Yang and Hrvoje Petek, ?The superatom states of fullerenes and their hybridization into the nearly free electron bands of fullerites?, ACS Nano, 3, 853 (2009)
J. Zhao, J. Yang, H. Petek, "Theoretical study of the molecular and electronic structure of methanol on a TiO2(110) surface." Phys. Rev. B 80 (2009) 235416-11.
J. Zhao, N. Pontius, A. Winkelmann, V. Sametoglu, A. Kubo, A. G. Borisov, D. Sánchez-Portal, V. M. Silkin, E. V. Chulkov, P. M. Echenique, and H. Petek, “The electronic potential of a chemisorption interface� Phys. Rev. B (in press).
J. Zhao, N. Pontius, A. Winkelmann, V. Sametoglu, A. Kubo, A. G. Borisov, D. Sánchez-Portal, V. M. Silkin, E. V. Chulkov, P. M. Echenique, and H. Petek, “The electronic potential of a chemisorption interface” Phys. Rev. B 085419 (2008).
Petek H, and J Zhao. 2010. "Ultrafast Interfacial Proton-Coupled Electron Transfer." Chemical Reviews 110(12):7082-7099. doi:10.1021/cr1001595).
T. Minato, Y. Sainoo, Y. Kim, H.S. Kato, K.-i. Aika, M. Kawai, J. Zhao, H. Petek, T. Huang, W. He, B. Wang, Z. Wang, Y. Zhao, J. Yang, and J.G. Hou, "The electronic structure of oxygen atom vacancy and hydroxyl impurity defects on titanium dioxide (110) surface," The Journal of Chemical Physics 130, 124502 (2009).
Wang LM, V Sametoglu, A Winkelmann, J Zhao, and H Petek. 2011. "Two-Photon Photoemission Study of the Coverage-Dependent Electronic Structure of Chemisorbed Alkali Atoms on a Ag(111) Surface." Journal of Physical Chemistry A 115(34):9479-9484. doi:10.1021/jp111932r
Winkelmann A, V Sametoglu, J Zhao, A Kubo, and H Petek. 2007. "Angle-dependent Study of a Direct Optical Transition in the sp Bands of Ag(111) by One- and Two-photon Photoemission." Physical Review. B, Condensed Matter 76:195428 1-11. doi:10.1103/PhysRevB.76.195428
Zhao J, B Li, KD Jordan, J Yang, and H Petek. 2006. "Interplay Between Hydrogen Bonding and Electron Solvation on Hydrated TiO2(110)." Physical Review. B, Condensed Matter 73:195309-1-195309-10.