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.

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.

Oxide Free Nanomaterials for Energy Storage and Conversion Applications covers in depth topics on non-oxide nanomaterials involving transition metal nitrides, carbides, selenides, phosphides, oxynitrides based electrodes, & other non-oxide groups. The current application of nanostructured nonoxides involves their major usage in energy storage and conversion devices variety of applications such as supercapacitor, batteries, dye-sensitized solar cells and hydrogen production applications. The current application of energy storage devices involves their usage of nanostructured non-oxide materials with improved energy and power densities. In this book readers will discover the major advancements in this field during the past decades. The various techniques used to prepare environmentally friendly nanostructured non-oxide materials, their structural and morphological characterization, their improved mechanical and material properties, and finally, current applications and future impacts of these materials are discussed. While planning and fabricating non-oxide materials, the readers must be concern over that they ought to be abundant, cost-efficient and environment-friendly for clean innovation and conceivably be of use in an expansive choice of utilization. The book gives detailed literature on the development of nanostructured non-oxides, their use as energy related devices and their present trend in the industry and market. This book also emphasis on the latest advancement about application of these noble non-oxide based materials for photocatalytic water-splitting. Recent progress on various kinds of both photocatalytic and electrocatalytic nanomaterials is reviewed, and essential aspects which govern catalytic behaviours and the corresponding stability are discussed. The book will give an updated literature on the synthesis, potential applications and future of nanostructured non-oxides in energy related applications. This book is highly useful to researchers working in the field with diversified backgrounds are expected to making the chapter truly interdisciplinary in nature. The contents in the book will emphasize the recent advances in interdisciplinary research on processing, morphology, structure and properties of nanostructured non-materials and their applications in energy applications such as supercapacitors, batteries, solar cells, electrochemical water splitting and other energy applications. Thus, nanotechnology researchers, scientists and experts need to have update of the growing trends and applications in the field of science and technology. Further, the postgraduate students, scientists, researchers and technologists are need to buy this book. Offers a comprehensive coverage of the nanostructured non-oxide materials and their potential energy applications Examines the properties of nanostructured non-oxide materials that make them so adaptable Explores the mechanisms by which nanoparticles interact with each other, showing how these can be used for industrial applications Shows the how nanostructured non-oxide materials are used in a wide range of industry sectors, containing energy production and storage

"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." --

Since the discovery of graphene, two-dimensional nanomaterials including Transition metal dichalcogenides (TMDCs), Hexagonal Boron Nitride (hBN), non-layered compounds, black phosphorous, and Xenes with large lateral dimensions, have emerged as promising candidates for heterogenous electrocatalysis owing to their exceptional physical, chemical, and electronic properties. The tremendous opportunities of using 2D nanomaterials in electrochemical CO2 reduction arises from their unique properties and vast number of applications. Covering the fundamentals, properties, and applications, all aspects of 2D nanomaterial composites within carbon dioxide conversion are discussed. The industrial scale-up and new challenges that exist in the field of electrochemical reduction of carbon dioxide will also be presented. With chapters written by internationally recognized researchers, this state-of-the-art overview will serve the growing interest amongst academic and industrial researchers in understanding 2D nanomaterials composites, their hidden interfaces and nanoscale dispersion of the metal oxide with nanocomposites for specific uses in carbon dioxide conversion to chemicals for fuel applications. This book will be of interest to graduate students and researchers in materials science, energy, and environmental science, as well as those in industry.

Conversion of Water and CO2 to Fuels usingSolar Energy Comprehensive Resource for Understanding the Emerging Solar Technologies for Hydrogen Generation via Water Splitting and Carbon-based Fuel Production via CO2 Recycling Fossil fuel burning is the primary source of carbon in the atmosphere. The realization that such burning can harm the life on our planet, has led to a surge in research activities that focus on the development of alternative strategies for energy conversion. Fuel generation using solar energy is one of the most promising approaches that has received widespread attention. The fuels produced using sunlight are commonly referred to as “solar fuels.” This book provides researchers interested in solar fuel generation a comprehensive understanding of the emerging solar technologies for hydrogen generation via water splitting and carbon-based fuel production via CO2 recycling. The book presents the fundamental science, technologies, techno-economic analysis, and most importantly, the materials that are being explored to establish artificial methods of fuel production using solar energy. For the rapid advancement of the field, it is necessary for researchers, particularly for those who are new to the field, to have clear knowledge of various materials studied so far and their performance. For this reason, almost half of the book is dedicated to the discussions on materials and properties. Key topics discussed in the book include: Photocatalytic/photoelectrochemical processes that use semiconductor photocatalysts, including both ceramic and non-ceramic materials Photovoltaic assisted electrochemical processes Solar thermochemical processes Molecular photosynthesis Researchers and professionals in the fields of energy and materials and closely related science and engineering disciplines could use this book to aquire clear insights on both mainstream solar fuel technologies and those in the developmental stages.

This book presents research dedicated to solving scientific and technological problems in many areas of electronics, photonics and renewable energy. Energy and information are interconnected and are essential elements for the development of human society. Transmission, processing and storage of information requires energy consumption, while the efficient use and access to new energy sources requires new information (ideas and expertise) and the design of novel systems such as photovoltaic devices, fuel cells and batteries. Semiconductor physics creates the knowledge base for the development of information (computers, cell phones, etc.) and energy (photovoltaic) technologies. The exchange of ideas and expertise between these two technologies is critical and expands beyond semiconductors. Continued progress in information and renewable energy technologies requires miniaturization of devices and reduction of costs, energy and material consumption. The latest generation of electronic devices is now approaching nanometer scale dimensions, new materials are being introduced into electronics manufacturing at an unprecedented rate, and alternative technologies to mainstream CMOS are evolving. Nanotechnology is widely accepted as a source of potential solutions in securing future progress for information and energy technologies. Semiconductor Nanotechnology features chapters that cover the following areas: atomic scale materials design, bio- and molecular electronics, high frequency electronics, fabrication of nanodevices, magnetic materials and spintronics, materials and processes for integrated and subwave optoelectronics, nanoCMOS, new materials for FETs and other devices, nanoelectronics system architecture, nano optics and lasers, non-silicon materials and devices, chemical and biosensors, quantum effects in devices, nano science and technology applications in the development of novel solar energy devices, and fuel cells and batteries.