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.

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.

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.

Photochemical Splitting of Water: Fundamentals to Applications brings together information on photochemical water splitting for hydrogen production, covering basic concepts, mechanisms, instrumentation, experimental set-up, analysis, materials used as catalysts, innovative methods, and future opportunities. The book introduces the role of water splitting and hydrogen production in the current and future global energy mix and provides a basic understanding of the theories behind photochemical water splitting, instrumentation, experimental set-up, and the criteria for materials selection. Other sections offers thorough coverage of the use of specific cutting-edge active materials in photocatalytic and photoelectrocatalytic water splitting processes, discussing recent advances and future opportunities.The final chapters of the book focus on challenges, emerging trends, and key opportunities for the future, including tandem approaches that combine a solar cell with a suitably formulated water splitting cell. A glossary of technical terms is also included, providing a clear explanation of the main concepts. - Consolidates and analyzes the state-of-the-art in water splitting for hydrogen production - Offers case studies, visuals, and practical information to support selection, efficiency, and scale-up - Includes key concepts, fundamental methods, and the context of the future global energy landscape

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.

"The conversion of solar energy into hydrogen via water splitting process is one of the key sustainable technologies for future clean, storable and renewable source of energy. Therefore, development of stable and efficient photocatalyst material has been of immense interest, but with limited success. Here, we show that overall neutral water splitting can be achieved under ultraviolet (UV) and visible light irradiation using group-III nitride nanowire arrays grown by plasma-assisted molecular beam epitaxy. The Rhodium/Chromium-oxide core/shell nanoparticle decorated GaN nanowires show stable photocatalytic activity under UV irradiation, with the turnover number well exceeding any previously reported GaN particulate samples. Additionally, by tuning the surface Fermi-level with controlled Mg doping in GaN nanowires, we demonstrate that the internal quantum efficiency can be enhanced by nearly two orders of magnitude under UV irradiation. Furthermore, in order to utilize the abundant visible solar spectrum, we have designed a multi-band InGaN/GaN nanowire heterostructure, that can lead to stable hydrogen production from neutral (pH~7.0) water splitting under UV, blue and green light irradiation (up to ~ 560 nm), the longest wavelength ever reported. At ~440-450 nm wavelengths, the internal quantum efficiency is estimated to be ~ 13%. Moreover, we have designed a dual-band p-type InGaN/GaN nanowire heterostructure, wherein Mg doping is optimized both in GaN and InGaN nanowires to achieve stable and efficient overall water splitting under UV and visible light. An internal quantum efficiency of ~69% has been achieved for neutral (pH~7.0) water splitting, the highest value ever reported under visible light illumination (400-475 nm). Subsequently, we have demonstrated that the optical absorption edge of GaN nanowires can be reduced from 3.4 eV to 2.95 eV by introducing Mg-related acceptor and nitrogen vacancy related donor energy states. This band-engineered GaN nanowires exhibit stable overall water splitting under violet light (up to 450 nm). The internal quantum efficiency of Mg doped GaN nanowire reached ~43% at 375-450 nm. Detailed analysis further confirms the stable photocatalytic activity of the III-nanowire heterostructures. Finally, we have presented the first example of dye-sensitized InGaN nanowires for Hydrogen generation under green, yellow and orange solar spectrum (up to 610 nm). This work establishes the use of metal-nitrides as viable photocatalyst for solar-powered artificial photosynthesis for future large-scale hydrogen and methanol based economy." --

Solar-driven water splitting combines several attractive features for sustainable energy utilization. The conversion of solar energy to a type of storable energy has crucial importance. An alternative method to hydrogen production by solar energy without consumption of additional reactants is a hybrid system which combines photochemical and electro-catalytic reactions. The originality of this research lies in the engineering development of a novel photo-catalytic water splitting reactor for sustainable hydrogen production, and verification of new methods to enhance system efficiency. The scope of this thesis is to present a thorough understanding of complete photocatalytic water splitting system performance under realistic working conditions. In this dissertation, an experimental apparatus for hydrogen and oxygen production is designed and built at UOIT to simulate processes encountered in photo-catalytic and electro-catalytic water splitting systems. The hybridization of this system is investigated, and scale-up analysis is performed based on experimental data using a systematic methodology. The hydrogen production rate of approximately 0.6 mmol h-1 corresponds to a quantum efficiency of 75% is measured through illumination of zinc sulfide suspensions in a dual-cell reactor. Utilization of ZnS and CdS photo-catalysts to simultaneously enhance quantum yield and exergy efficiency is performed. The production rate is increased by almost 30% as compared with ZnS performance. In the next step, an oxygen production reactor is experimentally investigated to simulate processes encountered in electro-catalytic water splitting systems for hydrogen production. In this research, the effects of ohmic, concentration and activation losses on the efficiency of hydrogen production by water electrolysis are experimentally investigated. The electrochemical performance of the system is examined by controlling the current density, temperature, space, height, and electrolyte concentration. The experimental results show that there exists an optimum working condition of water electro-catalysis at each current density, which is determined by the controlling parameters. A predictive mathematical model based on experimental data is developed, and the optimized working conditions are determined. The oxygen evolving half-cell is also analyzed for different complete systems including photo-catalytic and electro-catalytic water splitting. An electrochemical model is developed to evaluate the over-potential losses in the oxygen evolving reaction and the effects of key parameters are analyzed. The transient diffusion of hydroxide ions through the membrane and bulk electrolyte is modeled and simulated for improved system operation. In addition, a new seawater electrolysis technique to produce hydrogen is developed and analyzed from energy and exergy points of view. In this regard, the anolyte feed after oxygen evolution to the cathode compartment for hydrogen production is examined. An inexpensive and efficient molybdenum-oxo catalyst with a turn-over frequency of 1,200 is examined for the hydrogen evolving reaction. The electrolyte flow rate and current density are parametrically studied to determine the effects on both bulk and surface precipitate formation. The mixing electrolyte volume and electrolyte flow rate are found to be significant parameters as they affect cathodic precipitation. Furthermore, a new hybrid system for hydrogen production via solar energy is developed and analyzed. In order to decompose water into hydrogen and oxygen without the net consumption of additional reactants, a steady stream of reacting materials must be maintained in consecutive reaction processes, to avoid reactant replenishment or additional energy input to facilitate the reaction. Supramolecular complexes [{(bpy)2Ru(dpp)}2RhBr2](PF6)5 are employed as the photo-catalysts, and an external electric power supply is used to enhance the photochemical reaction. A light-driven proton pump is used to increase the photochemical efficiency of both O2 and H2 production reactions. The maximum energy conversion of the system can be improved up to 14% by incorporating design modification that yields a corresponding 25% improvement in exergy efficiency. Moreover, a photocatalytic water splitting system is designed and analyzed for continuous operation on a large pilot-plant scale. A Compound Parabolic Concentrator (CPC) is presented for the sunlight-driven hydrogen production system. Energy and exergy analyses and related parametric studies are performed, and the effect of various parameters are analyzed, including catalyst concentration, flow velocity, light intensity, reactor surface absorptivity, and ambient temperature. Two methods of photo-catalytic water splitting and solar methanol steam reforming are investigated as two potential solar-based methods of catalytic hydrogen production. The exergy efficiency, exergy destruction, environmental impact and sustainability index are investigated for these systems, as well as exergoenvironmental analyses. The results show that a trade-off exists in terms of exergy efficiency improvement and CO2 reduction of the photo catalytic hydrogen production system. The exergo-economic study reveals the maximum hydrogen exergy price of 2.12, 0.85, and 0.47 $ kg-1 for production capacities of 1, 100, and 2000 ton day-1, respectively. These results are well below the DOE 2012 target and confirm the viability of this technology.

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.

The book explains the principles and fundamentals of photocatalysis and highlights the current developments and future potential of the green-chemistry-oriented applications of various inorganic, organic, and hybrid photocatalysts. The book consists of eleven chapters, including the principles and fundamentals of heterogeneous photocatalysis; the mechanisms and dynamics of surface photocatalysis; research on TiO2-based composites with unique nanostructures; the latest developments and advances in exploiting photocatalyst alternatives to TiO2; and photocatalytic materials for applications other than the traditional degradation of pollutants, such as carbon dioxide reduction, water oxidation, a complete spectrum of selective organic transformations and water splitting by photocatalytic reduction. In addition, heterogeneized polyoxometalate materials for photocatalytic purposes and the proper design of photocatalytic reactors and modeling of light are also discussed. This book appeals to a wide readership of the academic and industrial researchers and it can also be used in the classroom for undergraduate and graduate students focusing on heterogeneous photocatalysis, sustainable chemistry, energy conversion and storage, nanotechnology, chemical engineering, environmental protection, optoelectronics, sensors, and surface and interface science. Juan Carlos Colmenares is a Professor at the Institute of Physical Chemistry, Polish Academy of Sciences, Poland. Yi-Jun Xu is a Professor at the State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, China.