Theoretical studies of electronic structure and dynamics of photoactive molecule-solid interfaces
EMSL Project ID
47524
Abstract
The experimental and theoretical understanding of photocatalysis is of vital importance for the solar-to-chemical energy conversion and for environmental remediation. Photocatalytic conversion of light into chemical energy involves a series of complex photophysical and photochemical steps whereby light excites carriers in a semiconductor and the carriers in turn drive chemical transformations. Our research groups combine time-resolved-two-photon photoemission spectroscopy [TR-2PP; University of Pittsburgh (Pitt)], scanning tunneling microscopy [STM; University of Science and Technology of China (USTC)], and ab initio electronic structure theory (Pitt and USTC), with the goal of elucidating the role of surface electronic structure, photon and electron induced surface dynamics, and light and electron induced chemistry in photocatalysis on TiO2. The primary focus of the research will be on the electron and hole mediated chemical processes on a variety of TiO2 surfaces. Previously, we have discovered by experiment and theory the wet electron states on protic solvent covered rutile TiO2(110) surfaces, which are the lowest energy vertical electron acceptor states. In addition to electron driven processes, it is well known that the valance band holes in TiO2 are a potent oxidizing agents. Holes, however, are more difficult to study by experimental methods. With a newly acquired broadly tunable femtosecond laser source, it is now possible to study the ultrafast hole dynamics near the valence band maximum using time-resolved photoemission techniques. We have experimental evidence from TR-2PP and STM that the band gap excitation of carriers induces the deprotonation of methanol on TiO2. Whether this occurs via electrons or holes is unclear. Therefore, our theoretical methods will focus on the less well-known valence band electronic structure of protic solvent covered water and methanol surfaces. In addition to studies on photocatalysis, we will investigate the electronic structure of other novel molecular systems. In particular, by STM and theory we have discovered the atom-like superatom molecular orbitals (SAMO) of hollow molecules such as fullerenes. These states are remarkable because they exhibit metal-like intermolecular hybridization leading to formation of nearly free-electron bands. We plan to study such states in a variety of molecular materials, such as metal oxide nanotubes and zeolites in order to explore the possible role of SAMOs in catalytic systems. In particular, we will examine how small molecules such as water and methanol interact with SAMOs (we expect interaction with the wet electron states).
The Chinook supercomputing facilities at EMSL are essential for the large scale computing that is necessary to describe surfaces with large unit cells, the diffuse, unoccupied sates on molecule covered surfaces, and GW calculations of excitations at surfaces.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2012-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Argondizzo A, X Cui, C Wang, H Sun, H Shang, J Zhao, and H Petek. 2015. "Ultrafast Multiphoton Pump-probe Photoemission Excitation Pathways in Rutile TiO2(110)." Physical Review. B, Condensed Matter 91:155429. doi:10.1103/PhysRevB.91.155429
Dougherty DB, M Feng, H Petek, JT Yates, and J Zhao. 2012. "Band Formation in a Molecular Quantum Well via 2D Superatom Orbital Interactions." Physical Review Letters 109(26):266802. doi:10.1103/PhysRevLett.109.266802
Feng M, H Petek, Y Shi, H Sun, J Zhao, F Calaza, M Sterrer, and HJ Freund. 2015. "Cooperative Chemisorption-Induced Physisorption of CO2 Molecules by Metal-Organic Chains." ACS Nano 9(12):12124–12136. doi:10. 1021/acsnano. 5b05222
Feng M, H Sun, J Zhao, and H Petek. 2014. "Self-Catalyzed Carbon Dioxide Adsorption by Metal-Organic Chains on Gold Surfaces ." ACS Nano 8(8):8644–8652. doi:10.1021/nn5035026
Migani A, DJ Mowbray, A Iacomino, J Zhao, and H Petek. 2013. "Level Alignment of a Prototypical Photocatalytic System: Methanol on TiO2(110)." Journal of the American Chemical Society 135(31):11429–11432. doi:10.1021/ja4036994
Migani A, DJ Mowbray, J Zhao, and H Petek. 2014. "Quasiparticle Interfacial Level Alignment of Highly Hybridized Frontier Levels: H2O on TiO2(110)." Journal of Chemical Theory and Computation 11(1):239–251. doi:10.1021/ct500779s
Migani A, DJ Mowbray, J Zhao, H Petek, and A Rubio. 2014. "Quasiparticle Level Alignment for Photocatalytic Interfaces." Journal of Chemical Theory and Computation 10(5):2103-2110. doi:10.1021/ct500087v
Petek H. 2012. "Photoexcitation of adsorbates on metal surfaces: One-step or three-step." Journal of Chemical Physics 137(9):091704. doi:10.1063/1.4746801.
Sun H, DJ Mowbray, A Migani, J Zhao, H Petek, and A Rubio. 2015. "Comparing Quasiparticle H2O Level Alignment on Anatase and Rutile TiO2." ACS Catalysis 5:4242–4254. doi:10.1021/acscatal.5b00529
Wang Y, H Sun, S Tan, H Feng, Z Cheng, J Zhao, A Zhao, B Wang, Y Luo, J Yang, and JG Hou. 2013. "Role of Point Defects on the Reactivity of Reconstructed Anatase Titanium Dioxide (001) Surface." Nature Communications 4:2214. doi:10.1038/ncomms3214
Zhang S ,Wang C ,Cui X ,Wang Y ,Argondizzo A ,Zhao J ,Petek H 2016. "Time-resolved Photoemission Study of the Electronic Structure and Dynamics of Chemisorbed Alkali Atoms on Ru(0001)" Physical Review B 93(4):045401. 10.1103/PhysRevB.93.045401
Zhang W, L Liu, L Wan, L Liu, L Cao, F Xu, J Zhao, and Z Wu. 2015. "Electronic Structures of Bare and Terephthalic Acid Adsorbed TiO2(110)-(1 x 2) Reconstructed Surfaces: Origin and Reactivity of the Band Gap States." Physical Chemistry Chemical Physics. PCCP 17(31):20144-20153. doi:10. 1039/C5CP01298H
Zhao J, and H Petek. 2014. "Non-nuclear Electron Transport Channels in Hollow Molecules." Physical Review. B, Condensed Matter 90:075412. doi:10.1103/PhysRevB.90.075412
Zhao J, M Feng, DB Dougherty, H Sun, and H Petek. 2014. "Molecular Electronic Level Alignment at Weakly Coupled Organic Film/Metal Interfaces." ACS Nano 8(10):10988–10997. doi:10.1021/nn5049969
Zhao J, Q Zheng, H Petek, and J Yang. 2014. "Nonnuclear Nearly Free Electron Conduction Channels Induced by Doping Charge in Nanotube–Molecular Sheet Composites." Journal of Physical Chemistry A. doi:10.1021/jp410460m