Download or read book Study of Novel Metal Oxide Semiconductor Photoanodes for Photoelectrochemical Water Splitting Applications written by Tilak Poudel and published by . This book was released on 2019 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar hydrogen is one ideal and sustainable energy source to replace fossil fuel. Solar Photovoltaic (PV) cells normally generate electricity using sunlight, but it is renewable only as long as our sun shines. Converting sunlight into electricity is an efficient way to address energy crisis but harvesting solar energy in the form of chemical energy is a sustainable solution for fueling tomorrows. Storing energy in the form of hydrogen bond is more efficient not only because of its high energy density and but also it is a clean energy source. Hydrogen can be generated in a number of ways, including but not limited to steam reforming, thermolysis, and electrolysis. Photoelectrochemical (PEC) water splitting is one of the most promising methods for solar-to-chemical energy conversion. In order to address the need for clean and renewable energy, recent trends in global CO2 emissions and energy production are analyzed, and the photoelectrochemical properties of multi-metal oxide based thin films are presented. Bismuth vanadate (BiVO4), barium bismuth niobate (Ba2BiNbO6), and antimony vanadate (SbVO4) were investigated for use as photoelectrodes in PEC water splitting for solar hydrogen production. This dissertation starts with synthesis, deposition, and characterization of antimony vanadate and Sb alloyed bismuth vanadate thin films to observe their photoelectrochemical ability to split water. Antimony doping in bismuth vanadate thin films prompts to modify valence and conduction band edges of bismuth vanadate. It has been found that Sb alloying with less than 20% wt. improves the electron conductivity and consequently leads to significant enhancement of photocurrents without creating secondary phases. The hole mobility is further improved by incorporating NaF and metallic Ni on the surface of the electrode. The NaF incorporation is believed to reduce electron effective mass and therefore increased electron mobility by suppressing scattering centers. As a result, antimony doped thin films exhibited much improved performance in PEC water splitting as compared to pure sputtered BiVO4. The metallic Ni deposition on the surface of Sb-doped BiVO4 acted as electrode corrosion inhibitor. But we found that Ni topping can enhance the stability of electrode in strong acidic solutions at the cost of reducing its optical absorption and hence lowering its photon-to-electron conversion efficiency. However, surface modification of thin films using various stack structure and oxides coatings helped to enhance their stability along with the oxygen evolution catalysis. Large area Bi-based quaternary oxides (Ba2Bi1.4Nb0.6O6 and Ba2BiNbO6) were deposited using RF sputtering deposition and the effects of surface-modification was also investigated using various electrochemical methods. Thin film uniformity was obtained by incorporating oxygen gas in the sputtering plasma. Photoelectrochemical thin films with higher stability in aqueous solution and better corrosion resistant were fabricated, analyzed, and tested. Capacitance-voltage measurement was used to measure the chemical kinetics of interfacial electron transfer of the system. Charge-carrier mobility was extremely limited by the rate of recombination, while the surface chemistry was altered by using Oxygen Evolution Reaction (OER) catalysts. Using the OER catalysts significantly reduced the surface recombination losses thereby extending hole carrier lifetime. Finally, a novel, high-throughput, combinatorial approach for the material synthesis and screening of mixed-metal oxides for photoanode design was developed. This methodology relies on controlling stoichiometric ratio of different sputtering yield metal oxides. After fabrication, the photoelectrochemical properties of oxide electrodes can be fully characterized by using various optical and electrochemical technique.

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 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 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 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 and Group III nitride Nanomaterials for Photoelectrochemical Water Splitting written by Yi Yang and published by . This book was released on 2016 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrochemical (PEC) cell is a device generated hydrogen fuel through an environmentally friendly method. The earliest report should date back to 1972. Honda and Fujishima first demonstrated solar water splitting by using titanium dioxide as photoanode in the cell. Then extensive efforts have been devoted to improving the solar-to-hydrogen (STH) conversion efficiency and decreasing the cost. However, current the efficiency of PEC device was limited on finding out a suitable photoanode material. The ideal photoanode material should have a good bandgap, favorable bandgap position, chemically stable and low cost. Therefore, this thesis would focus on studying different photoanode materials including GaN, TiO2 and Fe2O 3 to achieve high PEC water oxidation performance. In this thesis, I will first designed GaN nanowires on carbon cloth via a chemical vapor deposition (CVD) method and demonstrated significant photoactivity for photoelectrochemical water oxidation. In addition, our group used to report a facile and general strategy to fundamentally improve the performance of TiO2 nanowires for PEC water splitting. However, there are some concerns about the real effects under higher hydrogen treated temperature as well as the stability of oxygen vacancies in TiO2. Therefore I investigated the effect of hydrogenation temperature and the stability of oxygen vacancies in TiO2 photoanodes. Furthermore, there are few reports about the study on the long term stability of TiO2 photoanode even though most scholars used to think TiO 2 belongs to one of the most stable photoanode materials. So I carried out the first long term photostability measurement on various phases TiO 2 photoanodes including rutile, anatase and mixed phased and found TiO 2 photoanodes were not stable as people expected. Then I investigated the mechanism of the instability of TiO2 and carried out two strategies to stabilize TiO2 materials in the PEC cell. Finally, I created a facile acid treated method on hematite to substantially enhance the PEC activity. I found the enhanced photocurrent is due to improved efficiency of charge separation as well as potential passivation of surface electron traps.

Download or read book Metal Oxide Semiconductors written by Zhigang Zang and published by John Wiley & Sons. This book was released on 2023-12-11 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxide Semiconductors Up-to-date resource highlighting highlights emerging applications of metal oxide semiconductors in various areas and current challenges and directions in commercialization Metal Oxide Semiconductors provides a current understanding of oxide semiconductors, covering fundamentals, synthesizing methods, and applications in diodes, thin-film transistors, gas sensors, solar cells, and more. The text presents state-of-the-art information along with fundamental prerequisites for understanding and discusses the current challenges in pursuing commercialization and future directions of this field. Despite rapid advancements in the materials science and device physics of oxide semiconductors over the past decade, the understanding of science and technology in this field remains incomplete due to its relatively short research history; this book aims to bridge the gap between the rapidly advancing research progress in this field and the demand for relevant materials and devices by researchers, engineers, and students. Written by three highly qualified authors, Metal Oxide Semiconductors discusses sample topics such as: Fabrication techniques and principles, covering vacuum-based methods, including sputtering, atomic layer deposition and evaporation, and solution-based methods Fundamentals, progresses, and potentials of p–n heterojunction diodes, Schottky diodes, metal-insulator-semiconductor diodes, and self-switching diodes Applications in thin-film transistors, detailing the current progresses and challenges towards commercialization for n-type TFTs, p-type TFTs, and circuits Detailed discussions on the working mechanisms and representative devices of oxide-based gas sensors, pressure sensors, and PH sensors Applications in optoelectronics, both in solar cells and ultraviolet photodetectors, covering their parameters, materials, and performance Memory applications, including resistive random-access memory, transistor-structured memory devices, transistor-structured artificial synapse, and optical memory transistors A comprehensive monograph covering all aspects of oxide semiconductors, Metal Oxide Semiconductors is an essential resource for materials scientists, electronics engineers, semiconductor physicists, and professionals in the semiconductor and sensor industries who wish to understand all modern developments that have been made in the field.

Download or read book Flame Synthesis and Doping of Metal Oxide Nanowires and Their Application in Solar Water Splitting written by Lili Cai and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Considering the increasing energy and environmental problems associated with the exhaustible fossil fuels, renewable energy conversion devices have attracted tremendous attention, which hold the promise to supply the fuel and electricity in a sustainable way. For many of these devices, such as batteries, fuel cells, solar cells and solar water splitting cells, metal oxides are very important functional materials due to their earth abundance, good stability and diverse properties. Recently nanowire-based metal oxides have enabled revolutionary advances in various energy conversion devices, because of their unique physical and chemical properties resulting from the high aspect ratio and large surface area. Despite their advantages, practical applications of metal oxide nanowires are hindered, as conventional synthesis methods have limitations for large scale production. Flame synthesis can potentially solve this large-scale production issue for metal oxide nanowires, given its demonstrated scalability in the industrial production of nanoparticles. However, only until very recently has flame synthesis been applied to metal oxide nanowires. More research is needed to develop advanced flame synthesis method for metal oxide nanowires, to understand the mechanism to well control the size, shape and compositions for reliable manufacture, and to evaluate their quality and functionalities in real devices. This thesis presents a novel flame vapor deposition method for the synthesis of metal oxide nanowires with the capabilities of rapid rate, good uniformity over large area and broad substrate choice. Through the investigation of growth mechanism, good control over the morphology and composition was achieved by tuning the process parameters such as fuel/air ratio, source temperature, substrate material and temperature. In addition to synthesis, flame-based doping method (sol-flame doping) was innovated for controllable doping of metal oxide NWs to modify the properties of host materials at the nanometer scale. This sol-flame doping method not only preserves the morphology and crystallinity of the host NWs, but also allows fine control over the dopant concentration by simply varying the concentration of dopant precursor solution. With this method, significant enhancement of the electrocatalytic activity towards oxygen evolution reaction was achieved for TiO2 NWs (up to 760 mV reduction of the overpotential), attributing to simultaneously improved surface charge transfer kinetics and increased bulk conductivity by doping. Finally, the flame-synthesized metal oxide nanowires were implemented as a photoanode in photoelectrochemical water splitting. By rational design and scalable fabrication, the WO3/BiVO4/Ni:FeOOH composite nanowire photoanode generated a high photocurrent of 4.5 mA/cm2 at a potential of 1.23 VRHE under simulated sunlight, which is among the highest produced by any WO3/BiVO4 based photoanodes. With the demonstrated rapid rate, good controllability and superior performance of the flame-produced metal oxide nanowires, these flame synthesis and doping methods can potentially enable future generation of energy devices by removing the barrier for large-scale production of tailored metal oxide nanowires.

Download or read book Metal Oxides for Next generation Optoelectronic Photonic and Photovoltaic Applications written by Vijay Kumar and published by Elsevier. This book was released on 2023-09-15 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxides for Next Generation Optoelectronic, Photonic and Photovoltaic Applications focuses on the optoelectronic, photonic and photovoltaic behaviors of metallic oxides and closely related phenomena, from elementary principles to the latest findings. Each chapter includes a comprehensive evaluation of the synthesis and characterization of the most relevant metal oxides nanostructures for each application. In addition, there is a focus on methods to tune the materials’ properties in order to improve devices performance. This book is suitable for researchers and practitioners in academia and industry working in the disciplines of materials science and engineering, chemistry and physics. Metal oxides are widely used in various optoelectronic devices, photonics, display devices, smart windows, sensors, optical components, energy-saving, and harvesting devices. Each application requires materials with their own specific properties. By controlling the particle size, shape, crystal structure, one can tune various properties of metal oxides viz. bandgap, absorption properties, conductivity, which alter the material for the specific application. Includes discussions of synthesis and characterization of metal oxides materials for applications in next-generation optoelectronic, photonic and photovoltaic devices Emphasizes material design strategies of metal oxide nanostructures Focuses on the optoelectronic, photonic and photovoltaic behaviors of metallic oxides and closely related phenomena, from elementary principles to the latest findings

Download or read book Electrochemical water splitting based on metal oxide composite nanostructures written by Aneela Tahira and published by Linköping University Electronic Press. This book was released on 2020-05-14 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: The occurrence of available energy reservoirs is decreasing steeply, therefore we are looking for an alternative and sustainable renewable energy resources. Among them, hydrogen is considered as green fuel with a high density of energy. In nature, hydrogen is not found in a free state and it is most likely present in the compound form for example H2O. Water covers almost 75% of the earth planet. To produce hydrogen from water, it requires an efficient catalyst. For this purpose, noble materials such as Pt, Ir, and Ru are efficient materials for water splitting. These precious catalysts are rare in nature, very costly, and are restricted from largescale applications. Therefore, search for a new earth-abundant and nonprecious materials is a hot spot area in the research today. Among the materials, nanomaterials are excellent candidates because of their potential properties for extended applications, particularly in energy systems. The fabrication of nanostructured materials with high specific surface area, fast charge transport, rich catalytic sites, and huge ion transport is the key challenge for turning nonprecious materials into precious catalytic materials. In this thesis, we have investigated nonprecious nanostructured materials and they are found to be efficient for electrochemical water splitting. These nanostructured materials include MoS2-TiO2, MoS2, TiO2, MoSx@NiO, NiO, nickeliron layered double hydroxide (NiFeLDH)/Co3O4, NiFeLDH, Co3O4, Cu-doped MoS2, Co3O4- CuO, CuO, etc. The composition, morphology, crystalline structure, and phase purities are investigated by a wide range of analytical instruments such as XPS, SEM, HRTEM, and XRD. The production of hydrogen/oxygen from water is obtained either in the acidic or alkaline media. Based on the functional characterization we believe that these newly produced nanostructured materials can be capitalized for the development of water splitting, batteries, and other energy-related devices.

Download or read book Inorganic Metal Oxide Nanocrystal Photocatalysts for Solar Fuel Generation from Water written by Troy K. Townsend and published by Springer Science & Business Media. This book was released on 2014-03-19 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Troy Townsend's thesis explores the structure, energetics and activity of three inorganic nanocrystal photocatalysts. The goal of this work is to investigate the potential of metal oxide nanocrystals for application in photocatalytic water splitting, which could one day provide us with clean hydrogen fuel derived from water and solar energy. Specifically, Townsend's work addresses the effects of co-catalyst addition to niobium oxide nanotubes for photocatalytic water reduction to hydrogen, and the first use of iron oxide 'rust' in nanocrystal suspensions for oxygen production. In addition, Townsend studies a nickel/oxide-strontium titanate nanocomposite which can be described as one of only four nanoscale water splitting photocatalysts. He also examines the charge transport for this system. Overall, this collection of studies brings relevance to the design of inorganic nanomaterials for photocatalytic water splitting while introducing new directions for solar energy conversion.

Download or read book Understanding and Enhancing the Photostability of Nanoporous Metal Oxide Thin Films for Solar Hydrogen Generation written by Kalyan Chakravarthi Chitrada and published by . This book was released on 2016 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar water splitting is an environmentally benign process which has received wide attention in the recent years as an alternate method for a clean and safe production of hydrogen. This process employs a semiconductor based photocatalyst, water, and sunlight to produce hydrogen. Metal-oxide based semiconductors are considered to be ideal photocatalytic materials because of their stability against photo-corrosion combined with relatively narrow energy band-gap, appropriately placed band edge positions with reference to oxygen and hydrogen energy levels, less scattering of charges due to wider valence band, high dielectric constant, natural abundance, and non-toxicity. In this dissertation, two metal oxide based semiconductors viz., iron (III) oxide and bismuth (III) oxide were investigated to understand and enhance their photo activity as photoanodes for solar water splitting application. Iron (III) oxide has a well suited band gap to capture solar spectrum but it suffers from inappropriately positioned band edges, recombination losses due to low electron mobility, and a small minority carrier diffusion length. However, it was hypothesized that the Iron (III) oxide might show interesting photoelectrochemical properties by alloying with 4f elements and shifting the conduction band minimum of the iron oxide favorably to more negative potentials. In the present study, a nanoporous iron oxide layer incorporated with Nd3+ and B3+ was synthesized by electrochemical anodization of a FeNdB alloy. The photoelectrochemical behavior of this oxide was compared with thermally oxidized FeNdB alloy and the iron oxides obtained by anodization and thermal oxidation of pure iron foil. Incorporation of Nd3+ and B3+ in the iron oxide showed a direct bandgap of 2.05 eV, an indirect bandgap of 1.9 eV and shifted the flatband potentials to --0.8 VAg/AgCl in 1 M KOH solution. The FeNdB oxide showed marginally better catalytic activity for the oxygen evolution reaction than pure iron oxide under dark conditions. The binary bismuth (III) oxide, in spite being a good photocatalytic material, did not receive as much attention as other bismuth based ternary oxides for photoelectrochemical water splitting application. In this present study, large surface area nanoporous bismuth oxide thin films were synthesized by the electrochemical anodization. These anodic oxides exhibited a dual layered structure having a planar inner oxide and nanoporous outer oxide. Effect of the nanoscale dimensions of the oxides on the photoelectrochemical behavior was studied to understand the charge transport, charge recombination behavior, and long term stability of the material. A maximum photo current density of 0.97 mA/cm2 was observed for the sample anodized at 10 V at 1.53 VRHE. The nanoporous anodic oxides showed a charge carrier density in the range of 1.2 x 1017 -- 4.8 x 1018 cm−3 without illumination and about 60% increase in the charge carrier density upon illumination. However a decay in photo current was observed for the bismuth oxide samples was due to accumulation of holes on the electrode surface. This hole-accumulation was mitigated by the addition of hole scavengers. Addition of hydrogen peroxide as hole scavenger increased the photo current density by about 4 times in 0.5 M Na2SO4 (pH: 5.8) electrolyte. Addition of H2O2 in 1 M KOH (pH: 13.7) showed an increase-decrease behavior and high photo current density of ~10 mA/cm2 at a bias potential of 0.65 VRHE . The high photo activity observed in this electrolyte was attributed to the in-situ formation of Bi2O4-x phase by the photo-conversion of the [beta]-Bi2O3 at the surface. The photo-converted Bi2O4-x has a smaller band gap (1.4 eV) and therefore harvested more light in the visible region. This in-situ formation of low band gap phases in the presence of H2O2 during solar water splitting is an interesting observation which has been reported for the first time and this will help design material with very high photo-activity.

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 Oxide Semiconductors for Solar to Chemical Energy Conversion written by Venkataraman Thangadurai and published by Trans Tech Publications Ltd. This book was released on 2016-08-16 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is focused on the materials and devices for solar-to-chemical energy conversion. The introductory paper, by Alim and Bak, considers the basic concepts of the light-induced water oxidation by oxide semiconductors. This paper is concentrated on the photoreactivity of metal oxides, such as TiO2, with water and the related charge transfer during partial and total oxidation. The second paper of Yang et al provides an overview on the performance of TiO2 as photoanode in photoelectrochemical water oxidation. The paper of Nasir et al considers application of BiVO4 as photoelectrode for the generation of solar hydrogen fuel using water as the raw material. The work of Pastuovic et al is a treatise on the application of accelerator-based nuclear techniques in the characterisation of oxide semiconductors for solar energy conversion. This volume is addressed to those interested in the progress of research in oxide materials for solar energy conversion.

Download or read book Design of Advanced Photocatalytic Materials for Energy and Environmental Applications written by Juan M. Coronado and published by Springer Science & Business Media. This book was released on 2013-05-27 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research for the development of more efficient photocatalysts has experienced an almost exponential growth since its popularization in early 1970’s. Despite the advantages of the widely used TiO2, the yield of the conversion of sun power into chemical energy that can be achieved with this material is limited prompting the research and development of a number of structural, morphological and chemical modifications of TiO2 , as well as a number of novel photocatalysts with very different composition. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a systematic account of the current understanding of the relationships between the physicochemical properties of the catalysts and photoactivity. The already long list of photocatalysts phases and their modifications is increasing day by day. By approaching this field from a material sciences angle, an integrated view allows readers to consider the diversity of photocatalysts globally and in connection with other technologies. Design of Advanced Photocatalytic Materials for Energy and Environmental Applications provides a valuable road-map, outlining the common principles lying behind the diversity of materials, but also delimiting the imprecise border between the contrasted results and the most speculative studies. This broad approach makes it ideal for specialist but also for engineers, researchers and students in related fields.

Download or read book Fabrication of Tungsten Oxide Thin Film on Stainless Steel by Sol gel Method written by Geoffrey Momanyi and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal oxide semiconductor materials such as tungsten oxide are promising candidates for use as photoanodes in solar water splitting. Tungsten oxide is an n-type semiconductor that was prepared on stainless steel 304 substrate and subsequently studied for water-splitting applications. This study investigated the effect of the annealing temperature and substrate cleaning reagents on the photoelectrochemical (PEC) properties of tungsten oxide thin films. The main method of synthesis employed was the sol-gel method. Tungsten oxide thin films were deposited from a precursor solution of peroxotungstic acid by doctor blading. The as-deposited amorphous WO3 films were further subjected to heat treatment at various annealing temperatures (200 °C, 300 °C, 400 °C, and 500 °C) to transform the amorphous material into polycrystalline WO3 nanostructures. Surface morphology, the crystallinity of the film, the thickness of the film, and photoelectrochemical properties were investigated using scanning electron microscopy, (SEM), X-ray diffractometry (XRD), stylus profilometry, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The optimal WO3 film, at a thickness of 5 μm and annealed at 400 °C, achieved a photocurrent density of 98.0 μA/cm2 at an applied voltage of 0.53 V vs Ag/AgCl. It is essential to treat the substrate with HNO3 to passivate the surface of the stainless-steel substrate with the Cr2O3 layer.

Download or read book Combinatorial Discovery and Optimization of the Composition Doping and Morphology of New Oxide Semiconductors for Efficient Photoelectrochemical Water Splitting written by and published by . This book was released on 2015 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing need for carbon free energy has focused renewed attention on solar energy conversion. Although photovoltaic cells excel at directly converting of solar energy to electricity, they do not directly produce stored energy or fuels that account for more than 75% of current energy use. Direct photoelectrolysis of water has the advantage of converting solar energy directly to hydrogen, an ideal non-carbon and nonpolluting energy carrier, by replacing both a photovoltaic array and an electrolysis unit with one potentially inexpensive device. Unfortunately no materials are currently known to efficiently photoelectrolyze water that are, efficient, inexpensive and stable under illumination in electrolytes for many years. Nanostructured semiconducting metal oxides could potentially fulfill these requirements, making them the most promising materials for solar water photoelectrolysis, however no oxide semiconductor has yet been discovered with all the required properties. We have developed a simple, high-throughput combinatorial approach to prepare and screen many multi component metal oxides for water photoelectrolysis activity. The approach uses ink jet printing of overlapping patterns of soluble metal oxide precursors onto conductive glass substrates. Subsequent pyrolysis produces metal oxide phases that are screened for photoelectrolysis activity by measuring photocurrents produced by scanning a laser over the printed patterns in aqueous electrolytes. Several promising and unexpected compositions have been identified.