The rapidly increasing global demand for energy, combined with the environmental impact of fossil fuels, has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. This dissertation will describe engineering of metal-oxide-semiconductor (MIS) photoelectrodes for application in solar water splitting. First, we show that a silicon-based photocathode with an epitaxial oxide capping layer can provide efficient and stable hydrogen production from water. In particular, we grow a thin epitaxial layer of strontium titanate (SrTiO3) directly on Si (001) by molecular beam epitaxy. Photogenerated electrons can be easily transported through this layer because of the conduction band alignment and lattice match between single crystalline SrTiO3 and silicon. The approach is used to create a metal-insulator-semiconductor photocathode that under broad-spectrum illumination at 100 mW/cm2 exhibits a maximum photocurrent density of 35 mA cm2 and an open circuit potential of 450 mV; there was no observable decrease in performance after 10 hours of operation in 0.5 M H2SO4. Then, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown. This approach allows the insulator to be thick, which enhances stability, while enabling low-resistance carrier transport as required for efficiency. This method can be applied to various-oxides, such as SiO2 and Al2O3. In addition, it is suitable for silicon, III-V, and other optical absorbers for both photocathodes and photoanodes. Finally, the thick metal-oxide layer can serve as a thin-film antireflection coating, which increases light absorption efficiency.

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.

Metal Oxides in Energy Technologies provides, for the first time, a look at the wide range of energy applications of metal oxides. Topics covered include metal oxides materials and their applications in batteries, supercapacitors, fuel cells, solar cells, supercapacitors, and much more. The book is written by an experienced author of over 240 papers in peer-reviewed journals who was also been recognized as one of Thomson Reuter's "World's Most Influential Scientific Minds in 2015. This book presents a unique work that is ideal for academic researchers and engineers. - Presents an authoritative overview on metal oxides in energy technologies as written by an expert author who has published extensively in the area - Offers up-to-date coverage of a large, rapidly growing and complex literature - Focuses on applications, making it an ideal resource for those who want to apply this knowledge in industry

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.

There has been a resurgence of interest in light-induced water splitting as the search for storable carbon neutral energy becomes more urgent. Although the history of the basic idea dates back more than four decades, efficient, economical and stable integrated devices have yet to be realized. In the continuing quest for such devices, the field of photoelectrochemistry is entering a new phase where the extraordinary interdisciplinary of the research and development efforts are opening new avenues. This aspect of current research effort is reflected in the chapters of this book, which encompass present thinking in the various disciplines such as materials science, photo-electrochemistry and interfaces that can contribute to realization of viable solar fuel generators. This book presents a blend of the background science and recent advances in the field of photoelectrochemical water splitting, and includes aspects that point towards medium to long term future realization. The content of the book goes beyond the more traditional approaches to the subject by including topics such as novel excitation energy processes that have only been realized so far in advanced photonics. The comprehensive overview of current activities and development horizons provided by the impressive collection of internationally renowned authors therefore represents a unique reflection of current thinking regarding water splitting by light.

Semiconductors for Photocatalysis, Volume 97 covers the latest breakthrough research and exciting developments in semiconductor photocatalysts and electrodes for water splitting and CO2 reduction. It includes a broad range of materials such as metal-oxides, metal-nitrides, silicon, III-V semiconductors, and the emerging layered compounds. New to this volume are chapters covering the Fundamentals of Semiconductor Photoelectrodes, Charge Carrier Dynamics in Metal Oxide Photoelectrodes for Water Oxidation, Photophysics and Photochemistry at the Semiconductor/Electrolyte Interface for Solar Water Splitting, V Semiconductor Photoelectrodes, III-Nitride Semiconductor Photoelectrodes, and Rare Earth Containing Materials for Photoelectrochemical Water Splitting Applications. In addition, the design and modeling of photocatalysts and photoelectrodes and the fundamental mechanisms of water splitting and CO2 reduction is also discussed. Features the latest breakthroughs and research and development in semiconductor photocatalysis, solar fuels, and artificial photosynthesis Covers a broad range of topics, including a wide variety of materials and many important aspects of solar fuels Includes in-depth discussions on materials design, growth and synthesis, engineering, characterization, and photoelectrochemical studies