Surface Photovoltage Spectroscopy On Nanostructured Photocatalysts And Photovoltaic Thin Films For Solar Energy Conversion

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Surface Photovoltage Spectroscopy on Nanostructured Photocatalysts and Photovoltaic Thin-films for Solar Energy Conversion

Author : Benjamin Nail
Publisher :
ISBN 13 : 9780355969412
Total Pages : pages
Book Rating : 4.9/5 (694 download)

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Book Synopsis Surface Photovoltage Spectroscopy on Nanostructured Photocatalysts and Photovoltaic Thin-films for Solar Energy Conversion by : Benjamin Nail

Download or read book Surface Photovoltage Spectroscopy on Nanostructured Photocatalysts and Photovoltaic Thin-films for Solar Energy Conversion written by Benjamin Nail and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar energy conversion has the potential to reduce society’s dependence on fossil fuels and to diminish the harmful effects of climate change by generating clean power from the sun. The process of solar hydrogen production by photocatalytic water splitting uses solar energy to generate hydrogen fuels from water and has been explored extensively in recent years as hydrogen is considered a very promising candidate for a clean and renewable solar fuel. However, only a limited number of earth-abundant photocatalysts have been shown to be active for visible-light driven H2 evolution. New advances also continue in photovoltaic (PV) technologies such as hybrid solar cells, devices composed of inorganic semiconductor quantum dots (QDs) mixed with organic conducting polymers. This dissertation will focus on the application of Surface Photovoltage Spectroscopy (SPS) to study photochemical charge transfer processes in nanoscale photocatalysts and on the characterization of charge transfer dynamics occurring in inorganic-organic hybrid solar cell films. Chapter 2 explores a photocatalytic nickel oxide nanoparticle system modified with platinum co-catalyst for photochemical hydrogen generation. Nanocrystals of NiO have increased p-type character and improved photocatalytic activity for hydrogen evolution from water in the presence of methanol as sacrificial electron donor. Surface photovoltage spectroscopy of NiO and NiO–Pt films on Au substrates indicate a metal Pt-NiO junction with 30 mV photovoltage that promotes carrier separation. The increased photocatalytic and photoelectrochemical performance of nano-NiO is due to improved minority carrier extraction and increased p-type character, as deduced from Mott–Schottky plots, optical absorbance, and X-ray photoelectron spectroscopy data. These results are relevant to the understanding of NiO-containing photocatalysts and to the electronic properties of nanoscale metal oxides and junctions. In Chapter 3, surface photovoltage spectroscopy (SPS) was used to study the intrinsic charge transfer properties and surface states of thin films of thiol, amine, carboxylic acid supported CdSe QDs on indium tin oxide (ITO) in the absence of an external bias or electrolyte. On ITO, the QD films give positive or negative photovoltage signals (-120 to +350 mV) under sub band gap and super band gap excitation (0.1 - 0.3 mW cm−2), depending on the ligand type present at the QD surface. Experimental photovoltage values are found to correlate with the LUMO energies of the CdSe QDs, obtained from the electrochemical reduction potential in tetra-n-butylammonium hexafluorophosphate electrolyte at unadjusted pH. This suggests the possibility that the built-in potential of the ITO-QD Schottky contacts is controlled by the electronic properties of the ligands. The findings shed new light on factors controlling photochemical charge separation in films of ligand-stabilized CdSe QDs. Chapter 4 presents a study of a nanoscale doped perovskite photocatalyst, chromium-doped strontium titanate (Cr:SrTiO3). The Cr:SrTiO3 nanoparticles form as well defined cubic-shaped nanocrystals with a mean diameter of 43.5 nm (±18.8 nm) and have homogeneous composition. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis shows that Cr:SrTiO3 particles synthesized at high temperature contain high concentrations of Cr6+ trap sites while hydrothermally synthesized particles contain only Cr3+. SPS data shows that photogenerated charge carriers from Cr3+ donor states can drive photochemical reactions (e.g methanol oxidation) at the particle surface and that those reaction rates are increased by previous light excitation of the film. SPS also shows a dependence of photovoltage magnitude on substrate work function that is explained by the built-in potential (V[subscript bi]) at the film-substrate interface. Photochemical hydrogen evolution experiments show rates of up to 85 [mu]mol/hr (1.56% AQE at 435 nm). Rates are strongly dependent on solution pH, Cr doping %, and particle synthesis method. A mild NaBH4 reduction treatment was shown to increase photocatalytic activity in Cr:SrTiO3 and decrease its Cr6+ concentration. Surface photovoltage spectroscopy (SPS) also reveals an anomalously increasing photovoltage with magnitude greater than the band gap of SrTiO3. A model is proposed to show that the unusually large photovoltage, as well as charge separation in Cr:SrTiO3 in general, can be explained by a light-activated ferroelectric effect that causes ordering of electric dipoles in the non-centrosymmetric Cr:SrTiO3 unit cells.

Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion

Author : Mary D. Archer
Publisher : World Scientific
ISBN 13 : 1860942555
Total Pages : 781 pages
Book Rating : 4.8/5 (69 download)

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Book Synopsis Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion by : Mary D. Archer

Download or read book Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion written by Mary D. Archer and published by World Scientific. This book was released on 2008 with total page 781 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, expert authors describe advanced solar photon conversion approaches that promise highly efficient photovoltaic and photoelectrochemical cells with sophisticated architectures on the one hand, and plastic photovoltaic coatings that are inexpensive enough to be disposable on the other. Their leitmotifs include light-induced exciton generation, junction architectures that lead to efficient exciton dissociation, and charge collection by percolation through mesoscale phases. Photocatalysis is closely related to photoelectrochemistry, and the fundamentals of both disciplines are covered in this volume.

Nanotechnology for Photovoltaics

Author : Loucas Tsakalakos
Publisher : CRC Press
ISBN 13 : 1420076752
Total Pages : 458 pages
Book Rating : 4.4/5 (2 download)

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Book Synopsis Nanotechnology for Photovoltaics by : Loucas Tsakalakos

Download or read book Nanotechnology for Photovoltaics written by Loucas Tsakalakos and published by CRC Press. This book was released on 2010-03-25 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current concerns regarding greenhouse gas-related environmental effects, energy security, and the rising costs of fossil fuel-based energy has renewed interest in solar energy in general and photovotaics in particular. Exploring state-of-the-art developments from a practical point of view, Nanotechnology for Photovoltaics examines issues in increas

Photochemical Charge Transfer in Nanostructured Photocatalysts for Solar Hydrogen Production

Author : Jiarui Wang
Publisher :
ISBN 13 : 9781339543994
Total Pages : pages
Book Rating : 4.5/5 (439 download)

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Book Synopsis Photochemical Charge Transfer in Nanostructured Photocatalysts for Solar Hydrogen Production by : Jiarui Wang

Download or read book Photochemical Charge Transfer in Nanostructured Photocatalysts for Solar Hydrogen Production written by Jiarui Wang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar energy is a promising sustainable energy source to reduce greenhouse gas emission from combustion of fossil fuels and slow down the global climate change. Solar hydrogen generation via photocatalytic water splitting is potentially the most cost-effective way to produce solar fuels, so the development of efficient photocatalysts is one of the most important targets for scientific research. However, the application of inorganic materials for solar water splitting is currently limited by our understanding of photochemical charge transfer on the nanoscale, where space charge layers are less effective for carrier separation. Therefore, this dissertation focuses on the preparation of well-defined photocatalysts for the water splitting reaction and on the characterization of photochemical charge transfer on their interfaces. This will be accomplished through the application of surface photovoltage and photoelectrochemical measurements, and with photocatalytic reactivity tests. Results from this study can guide the design of inorganic photocatalysts with improved efficiency for solar energy conversion into fuel. Chapter 2 describes surface photovoltage spectroscopy studies to measure the internal photovoltages in a hydrogen evolution photocatalyst, single crystalline platinum/ruthenium-modified Rh-doped SrTiO3 nanocrystals. Voltages of -0.88 V and -1.13 V are found between the light absorber and the Ru and Pt cocatalysts, respectively, and a voltage of -1.48 V for a Rh-doped SrTiO3 film on an Au substrate. The voltages shows that the Pt and Ru cocatalysts not only improve the redox kinetics but also aid charge separation in the absorber. The voltages with redox agents correlate well with the photocatalytic performance of the catalyst and are influenced by the built-in potentials of the donor-acceptor configurations, the physical separation of donors and acceptors, and the reversibility of the redox reaction. The photovoltage data also allow the identification of a photosynthetic system for hydrogen evolution (80 [mu]mol·g−11h−1) under visible light illumination (>400 nm) from 0.05 M aqueous K4[Fe(CN)6]. Chapter 3 shows that suspended p-Si nanowires obtained by etching of an Al-doped silicon wafer facilitate photochemical hydrogen evolution under visible light. The activity varies greatly between sacrificial donors and can be increased by attachment of MoS2 cocatalysts, which promote proton reduction and charge transfer at the silicon-MoS2 interface. Overall, the activity of suspended p-Si nanorods is limited by the stability of the material in neutral solutions. A basic or neutral environment with photo-excitation can lead to silicon corrosion. In 0.05 M ferrocyanide at pH 6.5, the hydrogen evolution rate for SiNW/MoS2 was as high as 106 [mu]mol (10mg)−1 h−1 accompanied by silicon corrosion. The rate without corrosion decreased to 0.64 [mu]mol (10mg)−1 h−1 at a lower pH of 4.7. With silicon corrosion, the rate also reached 117 [mu]mol (10mg)−1 h−1 in pH 6.5 0.05 M Na2SO3 solution and 678 [mu]mol (10mg)−1 h−1 in 0.1 M NaSH without pH control. Silicon corrosion was not found in formaldehyde and methanol solutions, but the rates of SiNW/MoS2 and SiNW were as low as 0.40 and 0.18 [mu]mol (10mg)−1 h−1 for methanol solution, and 0.71 and 0.27 [mu]mol (10mg)−1 h−1 for formaldehyde solution. The increased hydrogen evolution with silicon corrosion can be attributed to both electron donating of silicon and reduced charge transfer resistivity with the dissolution of surface oxide layer on silicon nanowires. These findings can improve the understanding of photochemistry of Si-MoS2 catalyst, and help avoiding silicon corrosion in photocatalysis.

Photoelectrochemistry and Photovoltaics of Layered Semiconductors

Author : A. Aruchamy
Publisher : Springer
ISBN 13 :
Total Pages : 380 pages
Book Rating : 4.3/5 (91 download)

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Book Synopsis Photoelectrochemistry and Photovoltaics of Layered Semiconductors by : A. Aruchamy

Download or read book Photoelectrochemistry and Photovoltaics of Layered Semiconductors written by A. Aruchamy and published by Springer. This book was released on 1992-01-31 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is devoted exclusively to the interfacial photoelectronic properties of the inorganic layered semiconductors investigated in solid state (Schottky and p-n) photovoltaic and photoelectrochemical (solid/electrolyte) cells. The results of extensive studies on the various interfacial and surface electronic characteristics, interfacial photoreactions and materials aspects of the layered semiconductors reported in the last fifteen years have been reviewed. The layered transition metal dichalcogenides have served as model compounds for the investigation of the details of photoelectrochemical processes and related studies involving surfaces. The layered semiconducting materials have been found to be promising solar cell materials. Significant energy conversion efficiencies have been realized in photoelectrochemical solar cells and in solid state photovoltaic cells. Novel studies including quantum size effects in layered semiconductors have been reported. UHV spectroscopic studies of the surfaces of important layered semiconductors have been given. Recent developments in the preparation of the layered materials have been summarized. New insights into the physical and chemical characteristics of this class of materials have been gained by the studies reported in this book. Highlights include: -- Data on optical and electronic properties of layered semiconductors; -- Solid state and semiconductor/electrolyte junction characteristics; -- Photovoltaic and photoelectrochemical solar cells based on layered materials; -- UHV spectroscopic studies of surfaces of layered semiconductors; -- Quantum size effects in layered semiconductor colloids; -- Novel layered material preparation techniques.

Nanostructured Photocatalysts

Author : Rabah Boukherroub
Publisher : Elsevier
ISBN 13 : 012817837X
Total Pages : 301 pages
Book Rating : 4.1/5 (281 download)

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Book Synopsis Nanostructured Photocatalysts by : Rabah Boukherroub

Download or read book Nanostructured Photocatalysts written by Rabah Boukherroub and published by Elsevier. This book was released on 2020-06-06 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured Photocatalysts: From Materials to Applications in Solar Fuels and Environmental Remediation addresses the different properties of nanomaterials-based heterogeneous photocatalysis. Heterogeneous nanostructured photocatalysis represents an interesting and viable technique to address issues of climate change and global energy supply. Sustainable hydrogen (H2) fuel production from water via semiconductor photocatalysis, driven by solar energy, is regarded as a viable and sustainable solution to address increasing energy and environmental issues. Similarly, photocatalytic reduction of CO2 with water for the production of hydrocarbons could also be a viable solution. Sections cover band gap tuning, high surface area, the short diffusion path of carriers, and more. Introduces the utilization of nanostructured materials in heterogeneous photocatalysis for hydrogen fuel production via water splitting Explains preparation techniques for different nanomaterials and hybrid nanocomposites, enabling improved sunlight absorption efficiency and enhanced charge separation Assesses the challenges that need to be addressed before this technology can be practically implemented, particularly of identifying cost-effective nanophotocatalysts

Nanostructured Photocatalyst via Defect Engineering

Author : Vitaly Gurylev
Publisher : Springer Nature
ISBN 13 : 3030819116
Total Pages : 388 pages
Book Rating : 4.0/5 (38 download)

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Book Synopsis Nanostructured Photocatalyst via Defect Engineering by : Vitaly Gurylev

Download or read book Nanostructured Photocatalyst via Defect Engineering written by Vitaly Gurylev and published by Springer Nature. This book was released on 2021-10-28 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book helps readers comprehend the principles and fundamentals of defect engineering toward realization of an efficient photocatalyst. The volume consists of two parts, each of which addresses a particulate type of defects. The first, larger section provides a comprehensive and rigorous treatment of the behaviour and nature of intrinsic defects. The author describes how their controlled introduction and consequent manipulation over concentration, distribution, nature and diffusion is one of the most effective and practical methodologies to modify the properties and characteristics of target photocatalytic materials. The second part of the book explains the formation of extrinsic defects in the form of metallic and non-metallic dopants and gives a detailed description of their characteristics as this approach is also often used to fabricate an efficient photocatalyst. Filling the gap in knowledge on the correlation between introduction of defects in various semiconducting materials and their photocatalytic performance, the book is ideal for graduate students, academics and researchers interested in photocatalysts, defect engineering, clean energy, hydrogen production, nanoscale advanced functional materials, CO2 deactivation, and semiconductor engineering.

Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion

Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

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Book Synopsis Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion by :

Download or read book Nanostructured and Photoelectrochemical Systems for Solar Photon Conversion written by and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Inorganic Nanocrystal Photocatalysts for Solar Energy Conversion

Author : Jing Zhao
Publisher :
ISBN 13 : 9781321610314
Total Pages : pages
Book Rating : 4.6/5 (13 download)

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Book Synopsis Inorganic Nanocrystal Photocatalysts for Solar Energy Conversion by : Jing Zhao

Download or read book Inorganic Nanocrystal Photocatalysts for Solar Energy Conversion written by Jing Zhao and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar energy conversion is considered one of the most promising renewable energy solutions for replacing fossil fuels and easing global climate change. Developing a cost-effective technology for solar energy utilization to compete with market grid price is among the top priorities of our scientific society. Photocatalytic water splitting, which utilizes solar energy to produce carbon-zero hydrogen fuels from water, holds great potential towards achieving this challenging mission. Photovoltaic (PV) devices, for converting solar energy to electricity, continue to witness technological advances in the 21st century. This dissertation is dedicated to the advancement of photocatalytic water splitting and photovoltaic technologies, including the search for inexpensive photocatalysts with high efficiency, the fundamental understanding of photo-induced charge separation processes and the advanced instrumentation for probing photovoltage generation on the nanoscale. Chapter 2 starts off with the effect of quantum size confinement on the photocatalytic hydrogen production by CdSe nanocrystals. The particle size of a well-defined CdSe nanocrystal series is systematically varied, and their size-dependent conduction/valence band energetics as well as their photocatalytic hydrogen evolution rates are characterized in details. This allows the construction of a quantitative correlation between particle size, energy level and photocatalytic activity for CdSe nanocrystals, following Butler-Volmer electron-transfer theory. Chapter 3 transitions into the study on WO3 photoanodes for photocatalytic oxygen evolution. The activity of WO3 photoanodes is greatly enhanced via an in-situ doping by electrochemical reduction. Investigations show that the moderate reduction boosts carrier concentration and conductivity in WO3, consequently an improved charge collection and an increased photocurrent response. This activation strategy is also proven to be applicable to other WO3 systems with a wide range of particle sizes. Chapter 4 introduces surface photovoltage spectroscopy (SPS) as a powerful sensitive technique for probing photon-induced charge separation processes in photocatalysts and PV systems. Calcium niobium oxide, a wide bandgap hydrogen evolution photocatalyst with a well-defined surface morphology, is selected as a model material for understanding the photovoltage generation and charge separation in photocatalyst system via SPS. Systematic studies reveal the dependence of photovoltage on photon wavelength, light intensity, defect density, film thickness, ambient environment, substrate property, and the relative Fermi-level difference at the interface. Chapter 5 continues the application of SPS technique for understanding charge separation in CdSe nanocrystalline films for inorganic-/organic- hybrid solar cells. Surface ligands on CdSe nanocrystals are found to have a dramatic impact on the photovoltage responses from CdSe films. The replacement of native ligands by halides and amines leads to electron traps at the particle surface. Chloride, among all halide ligands, is indicated as a promising short surface ligand for good photovoltage response, whereas bromide and iodide are found as detrimental hole traps.

Photoelectrochemical Solar Fuel Production

Author : Sixto Giménez
Publisher : Springer
ISBN 13 : 3319296418
Total Pages : 574 pages
Book Rating : 4.3/5 (192 download)

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Book Synopsis Photoelectrochemical Solar Fuel Production by : Sixto Giménez

Download or read book Photoelectrochemical Solar Fuel Production written by Sixto Giménez and published by Springer. This book was released on 2016-04-29 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the conversion for solar energy into renewable liquid fuels through electrochemical reactions. The first section of the book is devoted to the theoretical fundamentals of solar fuels production, focusing on the surface properties of semiconductor materials in contact with aqueous solutions and the reaction mechanisms. The second section describes a collection of current, relevant characterization techniques, which provide essential information of the band structure of the semiconductors and carrier dynamics at the interface semiconductor. The third, and last section comprises the most recent developments in materials and engineered structures to optimize the performance of solar-to-fuel conversion devices.

Investigation of Metal and Metal Oxide Nanomaterials for Solar Energy Conversion

Author : Mollie Rose Waller
Publisher :
ISBN 13 : 9781267663276
Total Pages : pages
Book Rating : 4.6/5 (632 download)

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Book Synopsis Investigation of Metal and Metal Oxide Nanomaterials for Solar Energy Conversion by : Mollie Rose Waller

Download or read book Investigation of Metal and Metal Oxide Nanomaterials for Solar Energy Conversion written by Mollie Rose Waller and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Power harnessed from the sun has the capacity to meet the energy demands of the entire planet. Here we present research in the areas of solar energy conversion accomplished by photochemical water splitting, to produce renewable chemical fuels, and by photovoltaics, to generate electrical power. The entire discussion takes place within the context of nanochemistry. Investigation of the novel properties developed by materials when they become very small offers us new insight into the field of chemistry and provides us with unique ways of improving existing solar energy conversion technologies. Nanocrystalline tungsten trioxide, nano-WO3, is presented as a new photocatalyst for water oxidation in the presence of a sacrificial electron acceptor. The monoclinic structure of the nanomaterial is analyzed by powder X-ray diffraction and electron microscopy. Optical spectroscopy data is consistent with quantum confinement in nano-WO3. Comparison of the nanomaterial with the bulk phase, via surface photovoltage spectroscopy and electrochemical analysis, demonstrates that the principle photochemical and photophysical properties of tungsten trioxide are conserved upon nanoscaling. These results indicate that nano-WO3 has potential as a functional replacement for bulk WO3 in applications incorporating nanomaterials, such as ultrathin solar cells. The effects of nanosheet size and defect concentration are investigated for the known photocatalyst calcium niobate, TBA[Ca2Nb3O10]. The dimensions of the nanosheets, and the edge defect concentration, are controlled by ultrasonication and analyzed by optical and vibrational spectroscopy and high-resolution electron microscopy. The rate of photochemical hydrogen evolution from water, in the presence of a sacrificial electron donor, is shown to decrease linearly with sheet size. Surface photovoltage spectroscopy indicates a correlation between nanosheet size and charge carrier concentration that is consistent with photocatalytic activity being limited by charge recombination in edge defect sites. TBA[Ca2Nb3O10] nanosheets have previously been shown to photocatalytically split water into hydrogen and surface-bound peroxides. Peroxide formation is a result of incomplete water oxidation and eventually leads to deactivation of the catalyst. We present here the functionalization of the nanosheets with metal oxide nanoparticles as potential water oxidation co-catalysts, in an attempt to promote complete water splitting. The functionalized materials are well characterized using electron microscopy and optical, infrared, and Raman spectroscopies. However, a reduction in photocatalytic activity is observed following functionalization that can be explained in terms of competitive light absorption, electron-hole recombination, and electron trapping within the metal oxides. Finally, we present studies performed during the development of a one-pot synthesis for titanium dioxide nanospheres coated with silver shells (Ag@TiO2). Nanoscale silver demonstrates surface plasmon resonance (SPR) upon light absorption, and the incorporation of SPR exhibiting core–shell particles is reported to increase the efficiency of photovoltaic devices. Here we use photogenerated electrons within TiO2 to reduce silver onto the material surface as nanoseeds. The effects of silver concentration, reaction temperature, and photodeposition time on seed morphology and dispersion are presented, following analysis by electron microscopy. An electroless plating method utilizing acetaldehyde to chemically reduce additional silver is explored as a technique for shell formation following surface seeding. However, optical spectroscopy data indicates that seeds continue discrete growth, rather than merging into a shell. Ultimately, consistent silver seeding could not be achieved and shell formation was unsuccessful. The results of these studies are consistent with the conclusion that silver nucleation is limited by the photogeneration of electrons in TiO2, active site chemistry, and the inherent weakness of the Ag-TiO2 interaction.

Surface Photovoltage Spectroscopy Studies on Charge Separation in Dye-sensitized Photoelectrodes and Metal Oxide Photocatalysts for Solar Hydrogen Generation

Download Surface Photovoltage Spectroscopy Studies on Charge Separation in Dye-sensitized Photoelectrodes and Metal Oxide Photocatalysts for Solar Hydrogen Generation PDF Online Free

Author : Ruirui Han
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.5/5 (825 download)

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Book Synopsis Surface Photovoltage Spectroscopy Studies on Charge Separation in Dye-sensitized Photoelectrodes and Metal Oxide Photocatalysts for Solar Hydrogen Generation by : Ruirui Han

Download or read book Surface Photovoltage Spectroscopy Studies on Charge Separation in Dye-sensitized Photoelectrodes and Metal Oxide Photocatalysts for Solar Hydrogen Generation written by Ruirui Han and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water splitting photocatalysts and dye-sensitized solar cells (DSSCs) enable the conversion of solar energy to carbon free fuels and electricity. Development of these devices is an important step in achieving a sustainable energy economy. The energy conversion efficiencies of these systems are strongly affected by how well the photo-generated charge carriers can be separated at the interfaces to drive electrochemical reactions or to produce electrical power. This dissertation details the use of Surface Photovoltage Spectroscopy (SPS) to investigate these processes in a range of metal oxide photocatalysts and dye sensitized photoelectrodes. Chapter 2 describes work on the development of a novel tandem photocatalyst which consists of Ru-loaded SrTiO3 as the hydrogen evolving particle (HEP) and BiVO4 as the oxygen evolving particle (OEP). SPS was employed to assess the charge transfer between SrTiO3 and three hole acceptors (I-, [Fe(CN)6]4−, Fe2+) and that between BiVO4 and three electron acceptors (I3−, [Fe(CN)6]3−, Fe3+). Photocatalytic H2 and O2 evolution test reactions were then conducted with the aid of the redox shuttles. H2 and O2 production were proved to be feasible from Ru-loaded SrTiO3 in the presence of [Fe(CN)6]4− or Fe2+ and from BiVO4 in the presence of [Fe(CN)6]3− or Fe3+, separately. Finally, the water splitting reaction was carried out by combining the two half reaction systems. This work demonstrates a new approach to construct tandem system from HEP, OEP and electron mediators. Chapter 3 focuses on using SPS to analyze the charge injection efficiencies in dye-sensitized solar cells, specifically at the interfaces of dye/electron transport layer (ETL)/transparent conductive oxide (TCO). Three dyes (D35, Rose Bengal, Fluorescein), two ETLs (TiO2 and SrTiO3) and two TCOs (FTO and ITO) were studied. We find that the charge injection efficiency of each dye/ETL/TCO system obtained from SPS measurement was well correlated with the energy conversion efficiency of the corresponding DSSC. This study demonstrates that SPS is indeed a useful tool to screen dyes which might exhibit high performance as the sensitizer in DSSC. Chapter 4 focuses on the Fluorescein-sensitized Pt-loaded SrTiO3 system, which is able to produce H2 from water under visible light in the presence of a hole acceptor. The charge transfers between Fluorescein-sensitized SrTiO3 and four hole acceptors (I−, methanol, [Fe(CN)6]4− and triethanolamine - TEOA) were studied with SPS. The data helps to rationalize the trend for the photocatalytic H2 evolution activities observed with these hole acceptors. This study provides insights into the factors that limit the efficiency of the Fluorescein-sensitized SrTiO3 photocatalytic system. Lastly in Chapter 5, the mechanism for the light intensity-dependent photocatalytic activity of the tandem system composed of Ru-loaded Rh-doped SrTiO3 (HEP) and BiVO4 (OEP) was investigated by open circuit potential (OCP) measurements. The light intensity-dependent OCP measurements on the electrodes made of Ru-loaded Rh-doped SrTiO3 and BiVO4 revealed the effect of the solid-solid interfacial junction on charge carrier separation. This work also provides new insights into the reasons why the activity of the tandem photocatalyst exhibits strong light intensity dependence.

Improving the Optoelectronic Property and Photoactivity of Nano-structured Titanuim Dioxide

Author : Hong-Ying Lin
Publisher : ProQuest
ISBN 13 : 9780549821137
Total Pages : pages
Book Rating : 4.8/5 (211 download)

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Book Synopsis Improving the Optoelectronic Property and Photoactivity of Nano-structured Titanuim Dioxide by : Hong-Ying Lin

Download or read book Improving the Optoelectronic Property and Photoactivity of Nano-structured Titanuim Dioxide written by Hong-Ying Lin and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium dioxide (TiO 2) has been proven to be one of the most important and widely used photocatalyst for applications such as gas/liquid phase environmental cleaning, solar hydrogen generation, sensitized solar cell, UV filtration, etc. The biggest challenge in the applications of this semiconductor photocatalyst is its large band gap (~ 3.2 eV) which limits the utilizable spectrum of photons from the solar light (~ 4 to 5 %). To improve the optical sensitivity of TiO 2 in the visible light region, the band gap of TiO 2 needs to be tailored. The reduction of TiO 2 band gap can be achieved by controlling of its electronic structure via two routes: changing the particle size and doping it with impurities. To precisely control the size of TiO 2 particles, anatase TiO 2 nanocrystallines (17 to 29 nm) were synthesized by metallo-organic chemical vapor deposition (MOCVD) method with moderate control on system parameters (i.e. pressure and gas flow rates). The results of band gap change as a function of particle size agreed well with what was predicted using the Brus' effective mass model (EMM). However, the observations from photocatalytic oxidation of 2-chlorophenol (2-CP) showed that the smaller the particle size, the faster the degradation rate. This is attributed in part to the combined effect of band gap change relative to the spectrum of the light source and the specific surface area (or particle size) of the photocatalysts. Our results indicate that the gain in specific surface area due to the smaller particle size outweighs the improvement on its optical property (e.g. reduction in bandgap) under similar experimental condition. Our observation also showed the secondary particle size to be time dependent due to the aggregation and is highly correlated with its primary particle size. The nitrogen doped TiO 2 thin film synthesis was carried out with two different approaches: (1) oxidation of the titanium nitride (TiN) thin film and (2) reactive pulsed laser deposition (PLD). Nitrogen doping of TiO 2 in the former approach was done by the oxidation of TiN thin films at 800 ̊C in ambient air. The phase transformation of TiN to TiO 2 appears to be a function of annealing time. The X-ray photoelectron spectroscopy (XPS) studies have shown that the substitutionally doped TiO 2-x N x (N 1 s ~ 396 eV) remains stable only for the first two minutes of annealing. As the annealing proceeds, the N 1s XPS peak shifts to higher binding energy (N1 s ~ 400 and 402 eV) which indicates that binding energy of N atom shifted from substitutional site (Ti-N) to chemisorbed site (N=-N) when annealing process exceeds five minutes due to the substitution of Ti-N bond by Ti-O bond. Results from both depth profile XPS and cross-section TEM showed that the formation of TiO 2-x N x depends on the distance from the film surface. Film structure studied by X-ray diffraction (XRD) showed that mixed TiN and rutile TiO 2 phases formed between four and twenty four hours of annealing time. The optical properties were examined using UV-VIS spectroscopy. The most visible light sensitive samples showed ~65 to 105 nm red-shift on its absorption edges from that of pure TiO 2, which is equivalent to ~0.47 to 0.73 eV reduction in the effective bandgap. Our results suggest that surface oxidation of TiN is an effective method for the synthesis of band gap tailored oxides which have applications in photocatalysis, photovoltaic, etc. Doping of N into TiO 2 lattice was also achieved using the reactive pulsed laser deposition technique. The N concentration was controlled by adjusting the mixing ratio of make-up (N 2) and buffer (1:1 O 2 and Ar mixture) gases during laser ablation. (Abstract shortened by UMI.).

A Study of Semiconductor Candidates for Terrestrial Thin-film Photovoltaic Solar Energy Conversion

Author : Michael Sean Casey
Publisher :
ISBN 13 :
Total Pages : 420 pages
Book Rating : 4.:/5 (386 download)

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Book Synopsis A Study of Semiconductor Candidates for Terrestrial Thin-film Photovoltaic Solar Energy Conversion by : Michael Sean Casey

Download or read book A Study of Semiconductor Candidates for Terrestrial Thin-film Photovoltaic Solar Energy Conversion written by Michael Sean Casey and published by . This book was released on 1986 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Metal Nanocrystals

Author : Kallum M. Koczkur
Publisher : American Chemical Society
ISBN 13 : 0841299013
Total Pages : 164 pages
Book Rating : 4.8/5 (412 download)

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Book Synopsis Metal Nanocrystals by : Kallum M. Koczkur

Download or read book Metal Nanocrystals written by Kallum M. Koczkur and published by American Chemical Society. This book was released on 2020-07-31 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our society depends heavily on metals. They are ubiquitous construction materials, critical interconnects in integrated circuits, common coinage materials, and more. Excitingly, new uses for metals are emerging with the advent of nanoscience, as metal crystals with nanoscale dimensions can display new and tunable properties. The optical and photothermal properties of metal nanocrystals have led to cancer diagnosis and treatment platforms now in clinical trials, while, at the same time, the ability to tune the surface features of metal nanocrystals is giving rise to designer catalysts that enable more sustainable use of precious resources. These are just two examples of how metal nanocrystals are addressing important social needs.

Chemically Deposited Nanocrystalline Metal Oxide Thin Films

Author : Fabian I. Ezema
Publisher : Springer Nature
ISBN 13 : 3030684628
Total Pages : 926 pages
Book Rating : 4.0/5 (36 download)

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Book Synopsis Chemically Deposited Nanocrystalline Metal Oxide Thin Films by : Fabian I. Ezema

Download or read book Chemically Deposited Nanocrystalline Metal Oxide Thin Films written by Fabian I. Ezema and published by Springer Nature. This book was released on 2021-06-26 with total page 926 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book guides beginners in the areas of thin film preparation, characterization, and device making, while providing insight into these areas for experts. As chemically deposited metal oxides are currently gaining attention in development of devices such as solar cells, supercapacitors, batteries, sensors, etc., the book illustrates how the chemical deposition route is emerging as a relatively inexpensive, simple, and convenient solution for large area deposition. The advancement in the nanostructured materials for the development of devices is fully discussed.

Nanostructured Materials for Energy Related Applications

Author : Saravanan Rajendran
Publisher : Springer
ISBN 13 : 3030045005
Total Pages : 297 pages
Book Rating : 4.0/5 (3 download)

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Book Synopsis Nanostructured Materials for Energy Related Applications by : Saravanan Rajendran

Download or read book Nanostructured Materials for Energy Related Applications written by Saravanan Rajendran and published by Springer. This book was released on 2019-02-11 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the role and fundamental aspects of the diverse ranges of nanostructured materials for energy applications in a comprehensive manner. Advanced nanomaterial is an important and interdisciplinary field which includes science and technology. This work thus gives the reader an in depth analysis focussed on particular nanomaterials and systems applicable for technologies such as clean fuel, hydrogen generation, absorption and storage, supercapacitors, battery applications and more. Furthermore, it not only aims to exploit certain nanomaterials for technology transfer, but also exploits a wide knowledge on avenues such as biomass-derived nanomaterials, carbon dioxide conversions into renewable fuel chemicals using nanomaterials. These are the areas with lacunae that demand more research and application.