ATOMISTIC SIMULATION OF DISSIPATIVE CHARGE CARRIER DYNAMICS FOR PHOTOCATALYSIS

2012 ◽  
Vol 1390 ◽  
Author(s):  
Talgat M. Inerbaev ◽  
Dmitri S. Kilin ◽  
James Hoefelmeyer
Keyword(s):  
Charge Transfer ◽  
High Surface ◽  
High Surface Area ◽  
Oxidation Catalysis ◽  
Electron Hole ◽  
Charge Carrier Dynamics ◽  
Electron Hole Pair ◽  
Charge Transfer Dynamics ◽  
Reduced Density ◽  
Positively Charged

ABSTRACTPhoto-excitation of high surface area semiconductor nanorods decorated with surface catalyst particles are investigated. DFT-based simulation is applied to the charge transfer dynamics at the interface of the supported nanocatalyst by modeling dynamics of photo-excitations. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. The energy of photo-excitation is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling as the electron/hole pair relaxes to the conduction / valence band edges. The methodology is applied to TiO2 nanorod modeled as a periodic anatase (100) slab functionalized by minimalistic nano-clusters or doping. Simulations of these models demonstrate the formation of charge transfer state in both time and frequency domain. Computed charge dynamics leads to creation of positively charged areas on the nanorod surface that is an important prerequisite for oxidation catalysis. Our computation identifies optimal composition and morphology of nanocatalyst for such applications as water splitting for hydrogen production or solar cells.

Synthesis and Photocatalytic Properties of the Bi2MoO6 and Bi2WO6 Photocatalysts

2018 ◽  
Vol 768 ◽  
pp. 218-223
Author(s):  
Juan Xia ◽  
Lin Zhang ◽  
Qi Wang
Keyword(s):  
Light Absorption ◽  
Hydrothermal Reaction ◽  
Organic Dyes ◽  
High Surface ◽  
Diffuse Reflectance Spectrum ◽  
High Surface Area ◽  
Photocatalytic Properties ◽  
X Ray Diffraction ◽  
Electron Hole ◽  
One Pot

Two different Bi-based semiconductor photocatalysts Bi2MoO6 and Bi2WO6 were synthesized by a simple one-pot hydrothermal reaction at 453 K for 10 h. The properties of the photocatalysts, including structures, morphology, light-absorption band and photoluminescence, etc were characterized by X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectrum and fluorescence spectrum. Further, their photocatalytic properties were compared by the degradation of two different organic dyes: Rhodamine B and methylene blue. It is important to note that the Bi2WO6 nanoplate structure exhibited better photocatalytic activity than the Bi2MoO6 nanowires aggregates due to its high surface area, higher light absorption and lower recombination of electron-hole pairs.

scholarly journals Atomic Layer Deposition of GdCoO3 and Gd0.9Ca0.1CoO3

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 24
Author(s):  
Marion Duparc ◽  
Henrik Hovde Sønsteby ◽  
Ola Nilsen ◽  
Anja Olafsen Sjåstad ◽  
Helmer Fjellvåg
Keyword(s):  
Thin Films ◽  
Aspect Ratio ◽  
Atomic Layer Deposition ◽  
High Aspect Ratio ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Oxidation Catalysis ◽  
Post Annealing ◽  
Layer Deposition

Thin films of the catalytically interesting ternary and quaternary perovskites GdCoO3 and Gd0.9Ca0.1CoO3 are fabricated by atomic layer deposition using metal β-diketonates and ozone as precursors. The resulting thin films are amorphous as deposited and become single-oriented crystalline on LaAlO3(100) and YAlO3(100/010) after post-annealing at 650 °C in air. The crystal orientations of the films are tunable by choice and the orientation of the substrate, mitigated through the interface via solid face epitaxy upon annealing. The films exhibit no sign of Co2+. Additionally, high-aspect-ratio Si(100) substrates were used to document the suitability of the developed process for the preparation of coatings on more complex, high-surface-area structures. We believe that coatings of GdCoO3 and Gd1−xCaxCoO3 may find applications within oxidation catalysis.

scholarly journals In-Situ Synthesis of Nb2O5/g-C3N4 Heterostructures as Highly Efficient Photocatalysts for Molecular H2 Evolution under Solar Illumination

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 169 ◽  
Author(s):  
Faryal Idrees ◽  
Ralf Dillert ◽  
Detlef Bahnemann ◽  
Faheem Butt ◽  
Muhammad Tahir
Keyword(s):  
Photocatalytic Activity ◽  
Charge Carrier ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Photogenerated Electron ◽  
Band Alignment ◽  
Solar Irradiation ◽  
Electron Hole ◽  
The Impact

This work focuses on the synthesis of heterostructures with compatible band positions and a favourable surface area for the efficient photocatalytic production of molecular hydrogen (H2). In particular, 3-dimensional Nb2O5/g-C3N4 heterostructures with suitable band positions and high surface area have been synthesized employing a hydrothermal method. The combination of a Nb2O5 with a low charge carrier recombination rate and a g-C3N4 exhibiting high visible light absorption resulted in remarkable photocatalytic activity under simulated solar irradiation in the presence of various hole scavengers (triethanolamine (TEOA) and methanol). The following aspects of the novel material have been studied systematically: the influence of different molar ratios of Nb2O5 to g-C3N4 on the heterostructure properties, the role of the employed hole scavengers, and the impact of the co-catalyst and the charge carrier densities affecting the band alignment. The separation/transfer efficiency of the photogenerated electron-hole pairs is found to increase significantly as compared to that of pure Nb2O5 and g-C3N4, respectively, with the highest molecular H2 production of 110 mmol/g·h being obtained for 10 wt % of g-C3N4 over Nb2O5 as compared with that of g-C3N4 (33.46 mmol/g·h) and Nb2O5 (41.20 mmol/g·h). This enhanced photocatalytic activity is attributed to a sufficient interfacial interaction thus favouring the fast photogeneration of electron-hole pairs at the Nb2O5/g-C3N4 interface through a direct Z-scheme.

Doping Mo on Tungsten Oxide Thin Film and Photoelectrochemical Measurement

2021 ◽  
Vol 21 (9) ◽  
pp. 4813-4817
Author(s):  
Sang-Hyeok Yoon ◽  
Kyo-Seon Kim
Keyword(s):  
Thin Film ◽  
Tungsten Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Single Step ◽  
Oxide Thin Film ◽  
Mo Doping ◽  
Chemical Bonding State ◽  
Electron Hole Pair ◽  
Molybdenum Doping

Tungsten oxide (WO3) is semiconductor material which can be used for various applications. Especially, one-dimensional (1-D) nanostructured WO3 shows the high photoelectrochemical (PEC) performance due to high surface area and short transport route of electron–hole pair. The flame vapor deposition (FVD) process is an efficient and economical method for preparation of the 1-D nanos-tructured WO3 thin film. Molybdenum doping is a well-known method to improve the PEC performance of WO3 by reducing band gap and increasing electrical property. In this study, we prepared the 1-D WO3 nanostructures doped with Mo by FVD single step process. We confirmed that Mo was successfully doped on WO3 without changing significantly the original nanostructure, crystal structure and chemical bonding state of WO3 thin film. As a result of PEC measurement, the pho-tocurrent densities of WO3 thin film with Mo doping were higher by about 1.4 to 2 times (for applied voltage above 0.7 V vs. SCE) than those without Mo doping.

scholarly journals Interplay of Direct and Indirect Charge Transfer Pathways in Donor-Bridge-Acceptor Systems

2019 ◽  
Author(s):  
Junjie Liu ◽  
Dvira Segal
Keyword(s):  
Charge Transfer ◽  
Quantum Interference ◽  
Transport Processes ◽  
Electronic Coupling ◽  
Transfer Processes ◽  
Quantum Interference Effect ◽  
Donor Acceptor ◽  
Charge Transfer Dynamics ◽  
Reduced Density ◽  
Coherent Part

Charge transfer in donor-bridge-acceptor (DBA) structures typically takes place through the combination of donor-bridge and bridge-acceptor overlap integrals forming an effective, indirect electronic coupling between the donor (D) and acceptor (A) moieties. Here, we examine the effects of an additional direct DA electronic coupling on charge transfer processes in DBA systems with local interaction to thermal baths. First, using the exact Nakajima-Zwanzig master equation (NZME) for the reduced density matrix, we rigorously define probability currents as the coherent part of the NZME, thereby allowing us to quantify the contribution of the different electronic pathways (direct and indirect) to the charge transfer dynamics. Focusing on two minimal DBA systems of three sites (V and L models), and adopting well-developed methods, we find that the interplay between different transfer pathways can be assessed by the McConnell formula in the weak systembath coupling regime. We then demonstrate that the combination of indirect and direct donor-acceptor coupling either enhances or leads to a destructive quantum interference effect on charge transport processes, depending on the energy landscape of the DBA system.<br>

High-Surface-Area Architectures for Improved Charge Transfer Kinetics at the Dark Electrode in Dye-Sensitized Solar Cells

2014 ◽  
Vol 6 (11) ◽  
pp. 8646-8650 ◽  
Author(s):  
William L. Hoffeditz ◽  
Michael J. Katz ◽  
Pravas Deria ◽  
Alex B.F. Martinson ◽  
Michael J. Pellin ◽  
...  
Keyword(s):  
Solar Cells ◽  
Charge Transfer ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Dye Sensitized Solar Cells ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Development of High Surface Area Titania on Glass Fibre Supports for Photocatalysis

2014 ◽  
Vol 93 ◽  
pp. 196-202
Author(s):  
Pelin Yilmaz ◽  
Armando Marsden Lacerda ◽  
Igor Larrosa ◽  
Steve Dunn
Keyword(s):  
Visible Light ◽  
Surface Area ◽  
Glass Fibre ◽  
High Performance ◽  
Direct Injection ◽  
High Surface ◽  
Hydrothermal Process ◽  
High Surface Area ◽  
Electron Hole ◽  
Order Of Magnitude

We show that we have developed a hydrothermal process that produces a high surface area TiO2on glass fibre supports. The as produced titania shows good photocatalytic activity against a standard commercial dye – Rhodamine B– giving full decolourisation within 3 hours under UV and visible light irradiation. The samples are mechanically robust and can act as a photocatalytic filter for waste streams and pollutants. In addition to testing the standard titania we also photochemically deposit nanostructures of Pd. These hybrid catalysts show enhanced decolourisation by an order of magnitude over the native titania systems. This enhanced performance is due to the increased energy harvesting of the hybrid system through a visible light plasmon interaction and the direct injection of electrons from the noble metal into the adsorbed dye molecules. There is a clear relationship between the absorbed light and photochemical reactivity of the system which is further explained in terms of electron hole generation and separation and plasmonic interaction. In summary, we have generated a high performance catalyst that is produced on a bulk commodity substrate with enhanced activity due to control of the surface plasmon and direct band gap transition of electron hole pairs in the semi-conductor.

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