A surface science perspective on TiO2 photocatalysis

Bull. Chem. Soc. Jpn. への投稿のすすめ

Lung Wa Chung,† W. M. C. Sameera,‡ Romain Ramozzi,‡ Alister J. Page, Miho Hatanaka,‡ Galina P. Petrova, Travis V. Harris,‡,⊥ Xin Li, Zhuofeng Ke, Fengyi Liu, Hai-Bei Li, Lina Ding, and Keiji Morokuma*,‡ †Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China ‡Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano Nishihiraki-cho, Sakyo, Kyoto 606-8103, Japan Newcastle Institute for Energy and Resources, The University of Newcastle, Callaghan 2308, Australia Faculty of Chemistry and Pharmacy, University of Sofia, Bulgaria Boulevard James Bourchier 1, 1164 Sofia, Bulgaria Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, United States State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710119, China School of Ocean, Shandong University, Weihai 264209, China School of Pharmaceutical Sciences, Zhengzhou University, 100 Kexue Avenue, Zhengzhou, Henan 450001, China

The ONIOM Method and Its Applications

Yu Bai,†,‡ Ivań Mora-Sero,́ Filippo De Angelis, Juan Bisquert, and Peng Wang*,† †State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China ‡Institute of Chemistry and Energy Material Innovation, Academy of Fundamental Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, China Photovoltaic and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castello,́ Spain Istituto CNR di Scienze e Tecnologie Molecolari, c/o Dipartimento di Chimica, Universita ̀ di Perugia, via Elce di Sotto 8, I-06123 Perugia, Italy

Titanium Dioxide Nanomaterials for Photovoltaic Applications

In this review, we address the materials design parameters that control the processes of charge separation, and thereby device efficiency, in dye-sensitized photoelectrochemical solar cells. The review starts with an overview of the structure, energetics and kinetics of dye-sensitized solar cells. It then goes on to consider in more detail the parameters determining the efficiency of the two primary charge separation steps in these devices: electron injection from the dye excited state into the metal oxide electrode, and regeneration of the dye ground state by the redox electrolyte. We consider the kinetic competition between these desired charge separation steps and the undesired loss pathways of excited state decay to ground and electron recombination with dye cations. The review avoids detailed mathematical and spectroscopic discussion, but rather tries to summarize the key conclusions relevant to materials design. A recurring theme of the review is the energy cost of achieving charge separation, and h...

Electron Transfer Dynamics in Dye-Sensitized Solar Cells

Electron dynamics at molecular−bulk interfaces play a central role in a number of different fields, including molecular electronics and sensitized semiconductor solar cells. Describing electron behavior in these systems is difficult because it requires a union between disparate interface components, molecules and solid-state materials, that are studied by two different communities, chemists and physicists, respectively. This Account describes recent theoretical efforts to bridge that gap by analyzing systems that serve as good general models of the interfacial electron dynamics. The particular systems that we examine, dyes attached to TiO2, are especially important since they represent the key component of dye-sensitized semiconductor solar cells, or Gratzel cells. Gratzel cells offer a cheap, efficient alternative to traditional Si-based solar cells. The chromophore−TiO2 interface is a remarkably good target for theorists because it has already been the subject of many excellent experimental investigatio...

Dynamics of the photoexcited electron at the chromophore-semiconductor interface.

Nonadiabatic molecular dynamics combined with time-domain density functional theory are used to study electron transfer (ET) from a CdSe quantum dot (QD) to the C60 fullerene, occurring in several types of hybrid organic/inorganic nanocomposites. By unveiling the time dependence of the ET process, we show that covalent bonding between the QD and C60 is particularly important to ensure ultrafast transmission of the excited electron from the QD photon-harvester to the C60 electron acceptor. Despite the close proximity of the donor and acceptor species provided by direct van der Waals contact, it leads to a notably weaker QD-C60 interaction than a lengthy molecular bridge. We show that the ET rate in a nonbonded mixture of QDs and C60 can be enhanced by doping. The photoinduced ET is promoted primarily by mid- and low-frequency vibrations. The study establishes the basic design principles for enhancing photoinduced charge separation in nanoscale light harvesting materials.

Covalent Linking Greatly Enhances Photoinduced Electron Transfer in Fullerene-Quantum Dot Nanocomposites: Time-Domain Ab Initio Study

Vapor pressure grows rapidly above the boiling temperature, and past the critical point liquid droplets disintegrate. Our atomistic simulations show that this sequence of events is reversed inside carbon nanotubes (CNT). Droplets disintegrate first and at low temperature, while pressure remains low. The droplet disintegration temperature is independent of the CNT diameter. In contrast, depending on CNT diameter, a temperature that is much higher than the bulk boiling temperature is required to raise the internal pressure. The control over pressure by CNT size can be useful for therapeutic drug delivery.

Confinement by Carbon Nanotubes Drastically Alters the Boiling and Critical Behavior of Water Droplets

Wehavecombinedanalyticaltheorywithabinitio nonadiabatic molecular dynamics to study the phonon-induced relaxation of photoexcited charge carriers in PbSe and CdSe semiconductorquantumdots(QDs).Densityfunctionaltheory calculations show dense distributions of electronic levels near the energy gap, attributed to the reconstruction and lack of absolute symmetry of the QD surface. Most of these states are optically dark, but they do couple to phonons and facilitate charge carrier relaxation. The time-domain simulations show a complex, nonexponential relaxation, in agreement with the observed non-Lorenzian spectral line shapes. The relaxation accelerates athigherphotoexcitationenergiesduetobothahigherdensityofcarrierstatesandalargernonadiabaticelectronphononcoupling. Overtime,carrier relaxation changes fromGaussian toexponential. TheGaussian componentislargerinsmallerdots;this maybea manifestation of the phonon bottleneck effect. Since Markovian rate models give exponential decay, we suggest that the more complex form of the carrier relaxation, observed in our simulations, can be attributed to phonon memory. The analytic theory developed within the framework of quantized Hamilton dynamics rationalizes this observation. It shows that a detailed description of the phonon modes is more important than a model for the electronic states.

Victor V. Prezhdo

Papers

Dynamics of the photoexcited electron at the chromophore-semiconductor interface.

Covalent Linking Greatly Enhances Photoinduced Electron Transfer in Fullerene-Quantum Dot Nanocomposites: Time-Domain Ab Initio Study

Confinement by Carbon Nanotubes Drastically Alters the Boiling and Critical Behavior of Water Droplets

Theoretical Study of ElectronPhonon Relaxation in PbSe and CdSe Quantum Dots: Evidence for Phonon Memory

Synthesis and spectral-luminescent characteristics of N-substituted 1,8-naphthalimides