Toward Photochemical Water Splitting Using Band-Gap-Narrowed Semiconductors and Transition-Metal Based Molecular Catalysts PDF Download
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Category :
Languages : en
Pages :
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Book Description
We are carrying out coordinated theoretical and experimental studies of toward photochemical water splitting using band-gap-narrowed semiconductors (BGNSCs) with attached multi-electron molecular water oxidation and hydrogen production catalysts. We focus on the coupling between the materials properties and the H2O redox chemistry, with an emphasis on attaining a fundamental understanding of the individual elementary steps in the following four processes: (1) Light-harvesting and charge-separation of stable oxide or oxide-derived semiconductors for solar-driven water splitting, including the discovery and characterization of the behavior of such materials at the aqueous interface; (2) The catalysis of the four-electron water oxidation by dinuclear hydroxo transition-metal complexes with quinonoid ligands, and the rational search for improved catalysts; (3) Transfer of the design principles learned from the elucidation of the DuBois-type hydrogenase model catalysts in acetonitrile to the rational design of two-electron hydrogen production catalysts for aqueous solution; (4) Combining these three elements to examine the function of oxidation catalysts on BGNSC photoanode surfaces and hydrogen production catalysts on cathode surfaces at the aqueous interface to understand the challenges to the efficient coupling of the materials functions.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
We are carrying out coordinated theoretical and experimental studies of toward photochemical water splitting using band-gap-narrowed semiconductors (BGNSCs) with attached multi-electron molecular water oxidation and hydrogen production catalysts. We focus on the coupling between the materials properties and the H2O redox chemistry, with an emphasis on attaining a fundamental understanding of the individual elementary steps in the following four processes: (1) Light-harvesting and charge-separation of stable oxide or oxide-derived semiconductors for solar-driven water splitting, including the discovery and characterization of the behavior of such materials at the aqueous interface; (2) The catalysis of the four-electron water oxidation by dinuclear hydroxo transition-metal complexes with quinonoid ligands, and the rational search for improved catalysts; (3) Transfer of the design principles learned from the elucidation of the DuBois-type hydrogenase model catalysts in acetonitrile to the rational design of two-electron hydrogen production catalysts for aqueous solution; (4) Combining these three elements to examine the function of oxidation catalysts on BGNSC photoanode surfaces and hydrogen production catalysts on cathode surfaces at the aqueous interface to understand the challenges to the efficient coupling of the materials functions.
Author: Neelu Chouhan
Publisher: CRC Press
ISBN: 1315279630
Category : Science
Languages : en
Pages : 310
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Book Description
Cleavage of water to its constituents (i.e., hydrogen and oxygen) for production of hydrogen energy at an industrial scale is one of the "holy grails" of materials science. That can be done by utilizing the renewable energy resource i.e. sunlight and photocatalytic material. The sunlight and water are abundant and free of cost available at this planet. But the development of a stable, efficient and cost-effective photocatalytic material to split water is still a great challenge. To develop the effective materials for photocatalytic water splitting, various type of materials with different sizes and structures from nano to giant have been explored that includes metal oxides, metal chalcogenides, carbides, nitrides, phosphides, and so on. Fundamental concepts and state of art materials for the water splitting are also discussed to understand the phenomenon/mechanism behind the photoelectrochemical water splitting. This book gives a comprehensive overview and description of the manufacturing of photocatalytic materials and devices for water splitting by controlling the chemical composition, particle size, morphology, orientation and aspect ratios of the materials. The real technological breakthroughs in the development of the photoactive materials with considerable efficiency, are well conversed to bring out the practical aspects of the technique and its commercialization.
Author: Shady Abd El-Nasser
Publisher:
ISBN:
Category : Semiconductor rectifiers
Languages : en
Pages : 220
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Book Description
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.
Author: Samar Mohamed Fawzy Adam Shahin
Publisher:
ISBN:
Category : Metallic oxides
Languages : en
Pages : 180
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Book Description
Abstract: With the energy deficiency problem becoming more threatening, the need to find reliable and alternative energy resources is becoming inevitable. Hydrogen gas is considered a good and cleaner alternative due to its green combustion; and it is used in many applications. Accordingly, the use of solar energy in water splitting to produce hydrogen gas is attracting much attention. Finding the optimum semiconducting material that can efficiently absorb sun light and use it in charge carriers’ generation to split water into hydrogen and oxygen is a hot research topic; as many challenges exist in this regard. For instance, wide-bandgap semiconductors have enhanced stability, but absorption limited to the UV region. On the other hand, a lot of the narrow-bandgap semiconductors have poor stability in aqueous electrolytes. In this thesis we explore different effective pathways to overcome the wide band gap problem. In the first part, the fabrication of nanostructured Ti-Nb-Zr MPNTs via simple hard templating anodization method in an electrochemical bath using Formamide-based electrolyte is explained. The formation mechanism and growth model of the MPNTs is discussed using FESEM images. Optical properties are examined using UV-Vis as well as photoelectrochemical properties where the MPNTs have shown 9-fold enhancement in the photocurrent density over the compact counterpart. The MPNTs possess graded refractive index which was confirmed by ellipsometry measurement; and high light scattering owing to their large diameter. In the second part of the thesis, the MPNTs are annealed in three different gases Air, Oxygen and Hydrogen where a 26-fold enhancement was achieved in the H100 compared to Air and O100. XPS, XRD, and Raman scattering suggested the formation of a single mixed oxide under Air and Oxygen atmospheres, while Zr formed a second phase ZrTiO4 under the reducing atmosphere. XPS core spectra confirmed that Hydrogen annealing resulted in formation of valence band tail states and Ti3+ defects. A thorough discussion is presented on the defects present and their contribution to the water splitting process. Finally, CZTS is known to be a narrow-bandgap p-type semiconductor with absorption extending to the visible region. It was synthesized by a solvothermal method, and deposited by electrophoresis on the MPNTs annealed in Hydrogen. Despite of its instability in 1M KOH, a proof of concept was accomplished, as a great photocurrent enhancement was achieved
Author: Horst Kisch
Publisher: John Wiley & Sons
ISBN: 3527673334
Category : Science
Languages : en
Pages : 264
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Book Description
Focusing on the basic principles of semiconductor photocatalysis, this book also gives a brief introduction to photochemistry, photoelectrochemistry, and homogeneous photocatalysis. In addition, the author - one of the leading authorities in the field - presents important environmental and practical aspects. A valuable, one-stop source for all chemists, material scientists, and physicists working in this area, as well as novice researchers entering semiconductor photocatalysis.
Author: David James Martin
Publisher: Springer
ISBN: 3319184881
Category : Science
Languages : en
Pages : 170
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Book Description
This thesis describes novel strategies for the rational design of several cutting-edge high-efficiency photocatalysts, for applications such as water photooxidation, reduction, and overall splitting using a Z-Scheme system. As such, it focuses on efficient strategies for reducing energy loss by controlling charge transfer and separation, including novel faceted forms of silver phosphate for water photooxidation at record high rates, surface-basic highly polymerised graphitic carbon nitride for extremely efficient hydrogen production, and the first example of overall water splitting using a graphitic carbon nitride-based Z-Scheme system. Photocatalytic water splitting using solar irradiation can potentially offer a zero-carbon renewable energy source, yielding hydrogen and oxygen as clean products. These two ‘solar’ products can be used directly in fuel cells or combustion to provide clean electricity or other energy. Alternatively they can be utilised as separate entities for feedstock-based reactions, and are considered to be the two cornerstones of hydrogenation and oxidation reactions, including the production of methanol as a safe/portable fuel, or conventional catalytic reactions such as Fischer-Tropsch synthesis and ethylene oxide production. The main driving force behind the investigation is the fact that no photocatalyst system has yet reported combined high efficiency, high stability, and cost effectiveness; though cheap and stable, most suffer from low efficiency.
Author: S David Tilley
Publisher: Royal Society of Chemistry
ISBN: 1788014464
Category : Science
Languages : en
Pages : 302
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Book Description
Tremendous research is taking place to make photoelectrochemical (PEC) water splitting technology a reality. Development of high performance PEC systems requires an understanding of the theory to design novel materials with attractive band gaps and stability. Focusing on theory and systems analysis, Advances in Photoelectrochemical Water Splitting provides an up-to-date review of this exciting research landscape. The book starts by addressing the challenges of water splitting followed by chapters on the theoretical design of PEC materials and their computational screening. The book then explores advances in identifying reaction intermediates in PEC materials as well as developments in solution processed photoelectrodes, photocatalyst sheets, and bipolar membranes. The final part of the book focuses on systems analysis, which lays out a roadmap of where researchers hope the fundamental research will lead us. Edited by world experts in the field of solar fuels, the book provides a comprehensive overview of photoelectrochemical water splitting, from theoretical aspects to systems analysis, for the energy research community.
Author: Carlo Alberto Bignozzi
Publisher: Springer
ISBN: 9783642269820
Category : Science
Languages : en
Pages : 220
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Book Description
Metal Oxide Photoanodes for Water Splitting, by J. Augustynski, B. D. Alexander and R. Solarska; Hydrogen Production with Nanostructured and Sensitized Metal Oxides , by Stefano Caramori, Vito Cristino, Laura Meda, Roberto Argazzi and Carlo Alberto Bignozzi; Surface Nanostructures in Photocatalysts for Visible-Light-Driven Water Splitting, by Kazuhiko Maeda and Kazunari Domen; Artificial Photosynthesis Challenges: Water Oxidation at Nanostructured Interfaces, by Mauro Carraro, Andrea Sartorel, Francesca Maria Toma, Fausto Puntoriero, Franco Scandola, Sebastiano Campagna, Maurizio Prato and Marcella Bonchio; Photocatalytic Reduction of CO2: From Molecules to Semiconductors, by Tatsuto Yui, Yusuke Tamaki, Keita Sekizawa and Osamu Ishitani; Design of Heterogeneous Photocatalysts Based on Metal Oxides to Control the Selectivity of Chemical Reactions, by Andrea Maldotti and Alessandra Molinari;
Author: Jianmin Ma
Publisher: John Wiley & Sons
ISBN: 3527830073
Category : Technology & Engineering
Languages : en
Pages : 596
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Book Description
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.
Author: E. PELIZZETTI
Publisher: Springer Science & Business Media
ISBN: 9400946422
Category : Science
Languages : en
Pages : 720
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Book Description
Ever since the oil crisis of 1973, researchers in various fields of chemistry have proposed various schemes to conserve energy, as well to convert the sun's abundant and limitless supply of energy to produce chemical fuels (e. g. , hydrogen from water, . •. ). The enthusiasm had no previous parallel in the mid-1970's. Unfortunately, despite the several good proposals, the results have proven - in retrospect - somewhat disappointing from an economic viable point of view. The reasons for the meagre results are manyfold not the least of which are the experimental difficulties encountered in storage systems. Moreover, the lack of a concerted, well orchestrated interdisciplinary approach has been significant. By contrast, the chemical advances made in the understanding of the processes involved in such schemes have been phenomenal. A recent book on this issue ( M. Gratzel, Energy Resources through Photochemistry and Catalysis, 1983) is witness to the various efforts and approaches taken by researchers. In the recent years, many more groups have joined in these efforts, and the number of papers in the lit~rature is staggering ! One of the motives for organizing this NATO Advanced Research Workshop stemmed from our view that it was time to take stock of the accomplishments and rather than propose new schemes, it was time to consider seriously avenues that are most promising.
