Download or read book Growth and Characterization of Transition Metal Oxide Semiconductors for the Photoelectrochemical Oxidation of Water Using Visible Light written by Tyler Scott Matthews and published by . This book was released on 2013 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first chapter in this thesis presents an introduction and background motivation for artificial photosynthesis using transition metal oxide semiconductors. Also included is a section on some fundamental concepts of electrochemistry with semiconductors for the reader that may be unfamiliar with this research area. The second and third chapters are devoted to copper tungstate (CuWO4), an n-type semiconductor with a band gap of 2.0 eV that exhibits great promise as the photoanode in a z-scheme water-splitting device. The second chapter is in regards to CuWO4 thin films deposited via reactive-ion co-sputtering, while the third chapter presents a novel technique for the preparation of nanostructured CuWO4 with the aim of addressing some fundamental limitations when using 3rd-row transition metal oxide materials. In the second chapter, a detailed systematic study into the co-sputter growth conditions of CuWO4 will be presented with the aim of understanding the optimal growth parameters for photoelectrochemical applications. Structural and electronic characterization of the thin films will be presented to demonstrate the quality of the growth process. A thickness series was performed to determine the optimal thickness for maximizing photocurrent density. The photocurrent density reported in this thesis is the highest current density thus reported in the literature for CuWO4 at the thermodynamic water oxidation potential. A two-electrode experiment was performed in order to determine the feasibility of utilizing CuWO4 in a z-scheme device. A number of oxygen evolution reaction catalysts were deposited onto the surface of CuWO4 thin films and their effect on the overall current density will be discussed. Long-duration potentiostatic measurements were carried out over a wide range of pH values to ascertain the stability of the material, and a discussion into possible degradation mechanisms will be discussed. Finally, the efficacy of CuWO4 as a water oxidation catalyst will be demonstrated and discussed. The third chapter in this thesis shall discuss two novel approaches for the formation of nanostructured CuWO4 with the aim of overcoming the inherently poor minority carrier mobility that has thus far slowed limited photoelectrochemical applications of the material. In the first approach, anodic aluminum oxide nanotemplates were utilized in an attempt to electrochemically deposit CuWO4 nanowires into the pores. In the second approach, a novel nitric acid treatment on tungsten thin films was utilized to develop a nanostructured surface followed by incorporation of copper using an combined physical vapor deposition and subsequent annealing process. The overall results of both techniques will be discussed. The fourth and final chapter in this thesis is a report on the growth and characterization of a nickel iron oxide alloy material to serve as a photoanode. Thin films were grown via reactive-ion co-sputtering of nickel and iron metal targets in the presence of oxygen. Optical, structural, electronic, and photoelectrochemical characterization was performed and the results shall be discussed. Two appendices complete the work. The first appendix is a list of characterization and deposition instruments utilized throughout this body of work. The second appendix is a collection of Mathematica® programs developed during the course of the author's Ph. D. studies in order to aid in data collection and analysis.

Download or read book Metal Oxide Thin Films by Chemical Vapor Deposition for Photocatalytic Water Splitting written by Archana Sathyaseelan Panikar and published by . This book was released on 2016 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrochemical cells (PEC) are devices which convert solar energy into consumable chemical energy by splitting water into oxygen and hydrogen. Photocatalytic activity at a semiconductor oxide surface forms the backbone of the PEC and thus the quest for high activity oxide materials and improving the cells efficiency is a widely explored field of research. Metal oxide semiconductors with band gaps in the visible spectrum are actively sought as photocatalytic electrode materials. The major advantages are that oxides are nontoxic, stable, and inexpensive. However, their overall efficiency is usually limited by short carrier diffusion length due to structural defects, limited light absorptivity and sluggish kinetics at the interface. To overcome these limitations crystalline semiconductor oxides synthesized by high temperature techniques are desired. A direct liquid injection chemical vapor deposition technique has been employed to synthesize films of Fe2O3 (hematite) and BiVO4 (bismuth vanadate) for use as photocatalysts. The high temperature synthesis technique is optimized to obtain good quality crystalline smooth films on fluorine doped tin oxide substrates and their photoelectrochemical characteristics have been studied. It is observed that the interlayer oxide material used for growth of the Fe2O3 and BiVO4 has a significant role in their photoactivity.The interlayer oxide serves as an efficient electron transport layer and also influences the grain characteristics of the film. For hematite it is observed that a n-type metal oxide interlayer (e.g. Nb2O5 or TiO2) helps improve the photoactivity as compared to a p-type oxide (NiO). BiVO4 has a poor electron diffusion length, and a WO3 interlayer improves the photocurrent in BiVO4 films by improving the charge collection efficiency. The low absorption coefficient of hematite requires a dense electrode for greater light absorption; however, the electrode thickness is limited by the poor hole diffusion length (~4 nm). Plasmonic metal nanostructures of gold (Au), silver (Ag), and copper (Cu), which are known to concentrate and scatter broad range wavelengths of incident light, are promising for enhancing the light absorption cross-section of a semiconducting material. Gold nanoparticles embedded in hematite films have been synthesized. About three times higher light absorption and photocurrent enhancement are obtained. A thickness-dependent study of photoactivity indicates a greater enhancement of gold-embedded hematite thin films compared to thicker films due to reduced charge transport distance and optimal local field enhancement effect. The embedded structure also has the advantage of consistent performance and protection of plasmonic nanostructures from electrochemical corrosion, resulting in long cycles of operation.

Download or read book Visible Light Active Photocatalysis written by Srabanti Ghosh and published by John Wiley & Sons. This book was released on 2018-06-11 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and timely overview of this important and hot topic, with special emphasis placed on environmental applications and the potential for solar light harvesting. Following introductory chapters on environmental photocatalysis, water splitting, and applications in synthetic chemistry, further chapters focus on the synthesis and design of photocatalysts, solar energy conversion, and such environmental aspects as the removal of water pollutants, photocatalytic conversion of CO2. Besides metal oxide-based photocatalysts, the authors cover other relevant material classes including carbon-based nanomaterials and novel hybrid materials. Chapters on mechanistic aspects, computational modeling of photocatalysis and Challenges and perspectives of solar reactor design for industrial applications complete this unique survey of the subject. With its in-depth discussions ranging from a comprehensive understanding to the engineering of materials and applied devices, this is an invaluable resource for a range of disciplines.

Download or read book Photo and Electro Catalytic Processes written by Jianmin Ma and published by John Wiley & Sons. This book was released on 2022-01-25 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore green catalytic reactions with this reference from a renowned leader in the field Green reactions—like photo-, photoelectro-, and electro-catalytic reactions—offer viable technologies to solve difficult problems without significant damage to the environment. In particular, some gas-involved reactions are especially useful in the creation of liquid fuels and cost-effective products. In Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction, award-winning researcher Jianmin Ma delivers a comprehensive overview of photo-, electro-, and photoelectron-catalysts in a variety of processes, including O2 reduction, CO2 reduction, N2 reduction, H2 production, water oxidation, oxygen evolution, and hydrogen evolution. The book offers detailed information on the underlying mechanisms, costs, and synthetic methods of catalysts. Filled with authoritative and critical information on green catalytic processes that promise to answer many of our most pressing energy and environmental questions, this book also includes: Thorough introductions to electrocatalytic oxygen reduction and evolution reactions, as well as electrocatalytic hydrogen evolution reactions Comprehensive explorations of electrocatalytic water splitting, CO2 reduction, and N2 reduction Practical discussions of photoelectrocatalytic H2 production, water splitting, and CO2 reduction In-depth examinations of photoelectrochemical oxygen evolution and nitrogen reduction Perfect for catalytic chemists and photochemists, Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction also belongs in the libraries of materials scientists and inorganic chemists seeking a one-stop resource on the novel aspects of photo-, electro-, and photoelectro-catalytic reactions.

Download or read book Springer Handbook of Inorganic Photochemistry written by Detlef Bahnemann and published by Springer Nature. This book was released on 2022-06-25 with total page 1914 pages. Available in PDF, EPUB and Kindle. Book excerpt: The handbook comprehensively covers the field of inorganic photochemistry from the fundamentals to the main applications. The first section of the book describes the historical development of inorganic photochemistry, along with the fundamentals related to this multidisciplinary scientific field. The main experimental techniques employed in state-of-art studies are described in detail in the second section followed by a third section including theoretical investigations in the field. In the next three sections, the photophysical and photochemical properties of coordination compounds, supramolecular systems and inorganic semiconductors are summarized by experts on these materials. Finally, the application of photoactive inorganic compounds in key sectors of our society is highlighted. The sections cover applications in bioimaging and sensing, drug delivery and cancer therapy, solar energy conversion to electricity and fuels, organic synthesis, environmental remediation and optoelectronics among others. The chapters provide a concise overview of the main achievements in the recent years and highlight the challenges for future research. This handbook offers a unique compilation for practitioners of inorganic photochemistry in both industry and academia.

Download or read book Photoelectrochemical Water Splitting written by Zhebo Chen and published by Springer Science & Business Media. This book was released on 2013-08-28 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book outlines many of the techniques involved in materials development and characterization for photoelectrochemical (PEC) – for example, proper metrics for describing material performance, how to assemble testing cells and prepare materials for assessment of their properties, and how to perform the experimental measurements needed to achieve reliable results towards better scientific understanding. For each technique, proper procedure, benefits, limitations, and data interpretation are discussed. Consolidating this information in a short, accessible, and easy to read reference guide will allow researchers to more rapidly immerse themselves into PEC research and also better compare their results against those of other researchers to better advance materials development. This book serves as a “how-to” guide for researchers engaged in or interested in engaging in the field of photoelectrochemical (PEC) water splitting. PEC water splitting is a rapidly growing field of research in which the goal is to develop materials which can absorb the energy from sunlight to drive electrochemical hydrogen production from the splitting of water. The substantial complexity in the scientific understanding and experimental protocols needed to sufficiently pursue accurate and reliable materials development means that a large need exists to consolidate and standardize the most common methods utilized by researchers in this field.

Download or read book Oxide Semiconductors for Solar Energy Conversion written by Janusz Nowotny and published by CRC Press. This book was released on 2016-04-19 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxide semiconductors, including titanium dioxide (TiO2), are increasingly being considered as replacements for silicon in the development of the next generation of solar cells. Oxide Semiconductors for Solar Energy Conversion: Titanium Dioxide presents the basic properties of binary metal oxide semiconductors and the performance-related properties

Download or read book Atomic Layer Deposited Transition Metal Oxide titania Alloys for Solar Driven Water Oxidation written by Olivia L. Hendricks and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrochemical (PEC) water splitting is a promising approach for synthesizing chemical fuels from sunlight. First demonstrated by Fujishima and Honda in 1972, PEC cell components and design strategies have proliferated in recent years. Regardless of the specific device architecture, however, any efficient PEC device requires (1) a high yield of energetic photogenerated carriers and (2) a mechanism for extracting these photogenerated carriers, (3) a corrosion-resistant anode at the pH and operating potential of the device, and (4) an effective catalyst for water oxidation. This dissertation addresses these challenges in the context of a photoanode, where water oxidation is tightly coupled to one of the light-absorbing elements of the PEC device. Metal-insulator-semiconductor (MIS) junctions are a promising photoanode design that electronically couples a high-quality semiconductor to an efficient water oxidation catalyst. The photovoltage produced by an MIS junction depends on the strength of the built-in field, or Schottky barrier height. This built-in field, in turn, depends on the difference in work function between the semiconductor and the metal, taking charges and interface fields into account. For optimal performance, a high work function metal induces a field that sweeps photogenerated holes from an n-type semiconductor to the electrolyte interface for water oxidation. In addition to generating large photovoltages, the ideal Schottky contact to an n-type semiconductor photoanode must also catalyze water oxidation and protect the underlying semiconductor from corrosion. In this work, I use atomic layer deposition (ALD) to fabricate alloys of TiO2 and transition metal oxides (specifically RuOx and IrOx) that function as the "M" of an MIS photoanode. Alloying TiO2 with these noble metal oxides combines the corrosion resistance of TiO2 with the high work function and catalytic activity of RuOx and IrOx. These alloys represent an ultra-thin analogue to the dimensionally stable anode used industrially for chlorine evolution. By investigating the chemical and electronic properties of these alloys, I unravel some of the key design principles for corrosion resistant Schottky contacts in MIS photoanodes. First, I demonstrated that ALD TiO2 protects the underlying silicon from corrosion and stabilizes RuOx and IrOx during water oxidation in acid. Second, I found that the electronic properties of TiO2 could be altered by alloying with metal oxides that have the desired work function. TiO2 makes a poor Schottky contact to n-type silicon, and its conductivity is difficult to control. Alloying TiO2 with high work function, conductive metal oxides like RuOx or IrOx not only enables high photovoltages but also guarantees high conductivity. By comparing the electronic properties of TiO2-RuOx alloys with TiO2-IrOx alloys, I also determined that the density of states at the alloy/SiO2 interface was critical for charge transport through the MIS junction. Finally, I gained insight into the relationship between catalytic activity and stability for RuOx and IrOx, two of the most commonly used water oxidation catalysts in acid. While IrOx is more stable than RuOx, its catalytic activity nonetheless degrades slowly over time. Though I used silicon as a model semiconductor, this ALD alloying approach may be particularly valuable for semiconductors that must rely on MIS junctions to generate large photovoltages (because forming a p-n junction is problematic). ALD enables unusually precise control over both the film thickness and composition. The ability to create graded structures by ALD presents a unique opportunity to control the composition these protection layers as a function of depth, placing valuable metal atoms where they are needed most—at the electrode/electrolyte interface for catalysis and at the insulator/metal interface for efficient tunneling. As such, ALD is capable of addressing many of the challenges associated with fabricating carrier selective contacts in photoelectrochemical and photovoltaic devices.

Download or read book Marco Antonio Chaer Nascimento written by Fernando R. Ornellas and published by Springer Science & Business Media. This book was released on 2013-10-16 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Festschrift dedicated to the 65th birthday of Marco Antonio Chaer Nascimento, selected researchers in theoretical chemistry present research highlights on major developments in the field. Originally published in the journal Theoretical Chemistry Accounts, these outstanding contributions are now available in a hardcover print format. This volume will be of benefit in particular to those research groups and libraries that have chosen to have only electronic access to the journal. It also provides valuable content for all researchers in theoretical chemistry.

Download or read book Solar Energy Update written by and published by . This book was released on 1979 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photoelectrochemical Water Splitting written by Inamuddin and published by Materials Research Forum LLC. This book was released on 2020-04-05 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrochemical (PEC) water splitting is a highly promising process for converting solar energy into hydrogen energy. The book presents new cutting-edge research findings in this field. Subjects covered include fabrication and characteristics of various electrode materials, cell design and strategies for enhancing the properties of PEC electrode materials. Keywords: Renewable Energy Sources, Solar Energy Conversion, Hydrogen Production, Photoelectrochemical Water Splitting, Electrode Materials for Water Splitting, Transition Metal Chalcogenide Electrodes, Narrow Bandgap Semiconductor Electrodes, Ti-based Electrode Materials, BiVO4 Photoanodes, Noble Electrode Materials, Cell Design for Water Splitting.

Download or read book Fabrication and Characterization of Semiconductor Based Photo catalysis for Light Driven Water Splitting written by Shady Abd El-Nasser and published by . This book was released on 2017 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: he straightforward, low-priced and hence extensive conversion of sun light utilizing photocatalysis in a water splitting process is the main source to provide a clean and renwable hydrogen supply. Principally, photocatalysts are semiconductor materials with a suitable band gap that can absorb incident photons to produce photogeneated charges which consequently initiate the water splitting reaction to generate oxygen and hydrogen. The process itself is typically influenced by the material properties of the semiconductor (band gap, redox potentials and crystallinity) thus, altering the band structure of the semiconductor would help build up a photocatalyst that is appropriate for susbtaintial hydrogen generation. This thesis exemplifies a detailed study of high performance yet affordable photo-electrodes for solar-driven hydrogen production using Titanium (II) oxide (TiO2). Tio2 is considered to be a favorable photocatalyst that can be used as a photoanode in the photoelectrochemical cell due to its unique properties. In particular it's high physical and chemical stability, high oxidizing power of the photogenerated holes, low-cost and non-toxicity. However, TiO2 is ideal for water splitting only under ultraviolet (UV) light due to its band gap that reaches 3.2 eV which makes its photocatalytic activity only restricted to the UV range that comprises only about 3% of the whole solar spectrum. In this study, two titania based photoanode systems were investigated in an effort to optimize the trade-off between the low external bias needed (electrical energy input) and the high photocurrent spectral response (H2 output). In the first part, Na-modified TiO2 nanostructured electrodes were studied. Varying the Na content showed a noticeable impact on the optical as well as the photoelectrochemical characteristics. The morphological characterization affirmed the presence of a discontinuous layer adsorbed over the surface of the TiO2 nanotubes where the tublar structure is kept preserved after treatment. Chemical analysis revealed no significant change in the structural properties of TiO2 upon modification which proves that the alkali ions were just dispersed within the TiO2 network. Optical properties illustrate the inclusion of conduction band tail states attributed to the disordered structure where the absorption edge is slightly shifted towards higher wavelength regions. The modified electrodes maintained nearly 81 % enhancement in the photoconductivity (0.9928 mA cm-2) in comparison with that of bare TiO2 (0.1821 mA cm-2) under AM 1.5G illumination (100 mW cm-2, 0.05 M Ba (OH) 2). Also, improved carriers' separation and mobility has been accomplished which was asserted by the electrochemical impedance spectroscopy that revealed less charge transfer resistance as well as space charge capacitance for the surface modified electrodes. Further, the Mott-Schottky analysis affirmed the observed Voc enhancement by demonstrating a negative shift in the flat band potential for all the Na+-modified electrodes with respect to that of the pristine TiO2 implying less band bending requirements. Finally, DFT calculations were implemented to add further details on the electronic structure of the disordered titania confirming the empirical findings obtained upon surface modification. In the second part of this work, hybrid PEDOT/TiO2 photoelectrodes were analyzed. The development of such nanocomposites was accomplished by controlled electrochemical anodization of Ti foil, followed by a simple and fast spin coating of PEDOT. The heterojunctions maintained superior optical sensitivity where the absorption band edge reaches nearly l@ 694 nm with respect to that of the unsensitized (TiO2 l@ 382 nm). This clearly indicates the ability to promote water splitting under visible irradiation. Likewise, superior photoelectrochemical performance concerning the photoconductivity, and the charge transfer kinetics were recognized mainly due to the fact that the highest occupied molecular orbit (HOMO) and lowest unoccupied molecular orbit (LUMO) of PEDOT are more negative than the conduction band (CB) and the valence band (VB) of TiO2. This in return, not only narrows down the band gap but also facilitates the separation of photo-induced charges and accordingly improves the photocatalytic activity.

Download or read book Enhancing the Photoelectrochemical Water Splitting Characteristics of Titanium and Tungsten Oxide Based Materials Via Doping and Sensitization written by Ruchi Gakhar and published by . This book was released on 2015 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: To better utilize solar energy for clean energy production, efforts are needed to overcome the natural diurnal variation and the diffuse nature of sunlight. Photoelectrochemical (PEC) hydrogen generation by water splitting is a promising approach to harvest solar energy. Hydrogen gas is a clean and high energy capacity fuel. However, the solar-to-hydrogen conversion efficiency is determined mainly by the properties of the materials employed as photoanodes. Improving the power-conversion efficiency of PEC water splitting requires the design of inexpensive and efficient photoanodes that have strong visible light absorption, fast charge separation, and lower charge recombination rate. In the present study, PEC characteristics of various semiconducting photoelectrodes such as TiO2, WO3 and CuWO4 were investigated. Due to the inherent wide gap, such metal oxides absorb only ultraviolet radiation. Since ultraviolet radiation only composes of 4% of the sun's spectrum, the wide band gap results in lower charge collection and efficiency. Thus to improve optical absorption and charge separation, it is necessary to modify the band gap with low band gap materials.The two approaches followed for modification of band gap are doping and sensitization. Here, TiO2 and WO3 based photoanodes were sensitized with ternary quantum dots, while doping was the primary method utilized to investigate the modification of the band gap of CuWO4. The first part of this dissertation reports the synthesis of ternary quantum dot - sensitized titania nanotube array photoelectrodes. Ternary quantum dots with varying band gaps and composition (MnCdSe, ZnCdSe and CdSSe) were tethered to the surface of TiO2 nanotubes using successive ionic layer adsorption and reaction (SILAR) technique. The stoichiometry of ternary quantum dots was estimated to beMn0.095Cd0.95Se, Zn0.16Cd0.84Se and CdS0.54Se0.46. The effect of varying number of sensitization cycles and annealing temperature on optical and photoelectrochemical properties of prepared photoanodes were studied. The absorption properties and surface morphology of the sensitized tubes was analyzed using UV-visible spectroscopy and scanning electron microscopy. The phase composition was determined using X-Ray diffraction and X-ray photoelectron spectroscopy techniques. Electrodes were also evaluated for their stability using inductively coupled plasma optical emission spectrometry. Results show that the sensitization of TiO2 nanotubes with MnCdSe (8.79 mA/cm2), ZnCdSe (12.70 mA/cm2) and CdSSe (15.58 mA/cm2) resulted in up to a 30 fold increase in photocurrent compared to unsensitized nanotubes (0.4 mA/cm2). In the second part, the application of WO3 as photoanode for water splitting was explored. The porous thin films of WO3 films were sensitized with ternary quantum dots (ZnCdSe) using the SILAR technique. The structural, surface morphological and optical properties of the sensitized WO3 thin films were studied. PEC characteristics of the sensitized films were found to be 120 fold increase (8.53 mA/cm2) in comparison to that of unmodified WO3 films (0.07 mA/cm2). In the last part of this dissertation, CuWO4 was investigated as the potential photoanode material. The band gap of CuWO4 was estimated using density functional theory (DFT) calculations. The band structure was obtained using the first-principles plane wave self-consistent field (pwscf) method and the effect of nickel dopant on the band gap and optical properties of CuWO4 was evaluated. Theoretical calculations showed that doping led to a decrease in band gap. The validity of the theoretical approach was evaluated by experimentally synthesizing Ni-doped CuWO4 electrodes. Experimental results showed that the band gap indeed decreases when CuWO4 was doped with Ni, and thus validated the DFT approach. Ternary quantum dots were found to increase the PEC activity of TiO2 and WO3 based photoelectrodes by 120 fold. In addition, a method of computing band gap of semiconductor using DFT modeling was developed and validated with experimental results.

Download or read book Metal Oxide Semiconductors for Solar Energy Harvesting written by Elijah James Thimsen and published by . This book was released on 2009 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: The correlation between energy consumption and human development illustrates the importance of this societal resource. We will consume more energy in the future. In light of issues with the status quo, such as climate change, long-term supply and security, solar energy is an attractive source. It is plentiful, virtually inexhaustible, and can provide more than enough energy to power society. However, the issue with producing electricity and fuels from solar energy is that it is expensive, primarily from the materials (silicon) used in building the cells. Metal oxide semiconductors are an attractive class of materials that are extremely low cost and can be produced at the scale needed to meet widespread demand. An industrially attractive thin film synthesis process based on aerosol deposition was developed that relies on self-assembly to afford rational control over critical materials parameters such as film morphology and nanostructure. The film morphology and nanostructure were found to have dramatic effects on the performance of TiO2-based photovoltaic dye-sensitized solar cells. Taking a cue from nature, to overcome the spatial and temporal mismatch between the supply of sunlight and demand for energy consumption, it is desirable to produce solar fuels such as hydrogen from photoelectrochemical water splitting. The source of water is important -- seawater is attractive. The fundamental reaction mechanism for TiO2-based cells is discussed in the context of seawater splitting. There are two primary issues with producing hydrogen by photoelectrochemical water splitting using metal-oxide semiconductors: visible light activity and spontaneous activity. To address the light absorption issue, a combined theory-experiment approach was taken to understand the fundamental role of chemical composition in determining the visible light absorption properties of mixed metal-oxide semiconductors. To address the spontaneous activity issue, self-biasing all oxide p/n bulk-heterojunctions were synthesized and the nanostructure was systematically varied to understand the fundamental role of various characteristic length scales in the nanostructured region of the device on performance. The conclusion of this work is that solar energy harvesting by metal oxide semiconductors is highly promising. All of the scientific concepts have been proven, and steady gains in efficiency are being achieved as researchers continue to tackle the problem.

Download or read book Integration of Functional Oxides with Semiconductors written by Alexander A. Demkov and published by Springer Science & Business Media. This book was released on 2014-02-20 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the basic physical principles of the oxide/semiconductor epitaxy and offers a view of the current state of the field. It shows how this technology enables large-scale integration of oxide electronic and photonic devices and describes possible hybrid semiconductor/oxide systems. The book incorporates both theoretical and experimental advances to explore the heteroepitaxy of tuned functional oxides and semiconductors to identify material, device and characterization challenges and to present the incredible potential in the realization of multifunctional devices and monolithic integration of materials and devices. Intended for a multidisciplined audience, Integration of Functional Oxides with Semiconductors describes processing techniques that enable atomic-level control of stoichiometry and structure and reviews characterization techniques for films, interfaces and device performance parameters. Fundamental challenges involved in joining covalent and ionic systems, chemical interactions at interfaces, multi-element materials that are sensitive to atomic-level compositional and structural changes are discussed in the context of the latest literature. Magnetic, ferroelectric and piezoelectric materials and the coupling between them will also be discussed. GaN, SiC, Si, GaAs and Ge semiconductors are covered within the context of optimizing next-generation device performance for monolithic device processing.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1985 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photoelectrochemical Kinetics of Visible light Driven Water Splitting at Rh SrTiO3 Based Electrodes written by Manuel Antuch Cubillas and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The kinetics of water photo-dissociation assisted by visible light was the main topic of this work. The Rh doped SrTiO3 semiconductor was employed as photo-excitable material. It can absorb visible light and therefore transform solar energy into useful chemical fuels. In this manuscript, a wide bibliographic overview is provided in the 1st Chapter, covering a description of the characterization methods and current models for photoelectrochemical kinetics. The 2nd Chapter is devoted to the description of the materials and methods. The 3rd Chapter deals with the full photoelectrochemical kinetic characterization of water splitting with Rh:SrTiO3 photoelectrodes, surface-modified by addition of a model clathrochelate or with metallic Cu or Pt. In the 4th Chapter, a theoretical study of the mechanism of hydrogen evolution catalyzed by a model clathrochelate is provided. During the discussion, the EXAFS spectrum of the organometallic complex was thoroughly analyzed and modelled, and the relevant protonated intermediates involved in the mechanism were identified. The 5th Chapter deals with the photoelectrochemical dynamics of illuminated Rh:SrTiO3 -based photo-electrodes, characterized by the light-modulated photovoltage technique. Unusual results were obtained and are reported in this thesis for the first time. This unexpected dynamic behavior has been modelled by a set of classical differential equations usually used to describe such photo-processes.