First principles investigations on the coupling of polaron and excited carrier dynamics at TiO2/molecule interface
EMSL Project ID
49745
Abstract
We propose to perform computational studies of the structure and dynamics of polarons in TiO2 and related materials. The nature of charge carriers in photocatalytic semiconductors is crucial to their photocatalytic activity. There is increasing evidence that electrons in rutile and anatase polymorphs of TiO2 have polaronic character, but a fundamental theoretical description of how the polaronic nature affects the photocatalytic activity is still lacking. Time-resolved two photon photoemission (2PP) measurements performed in Petek's group at the university of Pittsburgh on reduced rutile TiO2 show that: 1) the defects states produced by reduction have strong polaronic character, which is exhibited by the temperature dependence of 2PP spectra; 2) adsorption of charge donating, amphoteric, and charge accepting molecules have pronounced, molecule-specific effects on the polaronic 2PP signal, indicating strong and specific interactions between molecules and the trapped charges. The sensitivity of 2PP spectra to the polaronic character derives from employing of the t2g - eg transition resonance in TiO2, which is particularly sensitive to polaronic distortions of the lattice. We propose to perform theoretical studies on the electronic structure of self-trapped and defect bound polarons in rutile and anatase TiO2 in the bulk, at surfaces, and in the presence of molecular decoration (H2O, CO2, CH3OH, H2CO, O2, etc.). The transition dipole moments will be calculated to enable the interpretation of 2PP spectroscopy of the quasi-particles and excited states. Furthermore, we will investigate the polaron dynamics using time-dependent nonadiabatic molecular dynamics (NAMD) method. We will study the excited carrier dynamics such as polaron hopping and electron-hole recombination coupled with the polaron, as well as how they are affected by molecular adsorption. The couplings of carriers with phonons at different temperatures will be analyzed based different approaches. The proposed theoretical research will strongly couple with the time-resolved two-photon photoemission spectroscopy experiments at the University of Pittsburgh. The proposed research will provide a deeper understanding of how the polaronic character of TiO2 affects its photocatalytic activity. It will utilize the EMSL high-performance computing for characterization and understanding of the experimental and theoretical basis of molecular-level reactions that occur in energy transduction and carbon recapture systems. Neither PI has in-house computing facilities that could accomplish the proposed research.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2017-10-01
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Sun H., S. Tan, M. Feng, J. Zhao, and H. Petek. 2018. "Deconstruction of the Electronic Properties of a Topological Insulator with a Two-Dimensional Noble Metal-Organic Honeycomb-Kagome Band Structure." Journal of Physical Chemistry C 122. doi:10.1021/acs.jpcc.8b03353
Zhang L., A.S. Vasenko, J. Zhao, and O.V. Prezhdo. 2019. "Mono-Elemental Properties of 2D Black Phosphorus Ensure Extended Charge Carrier Lifetimes under Oxidation: Time-Domain Ab Initio Analysis." Journal of Physical Chemistry Letters 10, no. 5:1083-1091. doi:10.1021/acs.jpclett.9b00042