Studies on structure-function relationships in functional metal oxide semiconductor photoelectrodes and inorganic-polymer composite materials

Metal oxides have interesting physical and electronic properties that have resulted great contributions to the field of catalysis, sensing, portable energy storage and photoelectrochemistry. As many of these applications rely on the interfacial area of the active metal oxide, it is important to tailor the surface composition and morphology in order to increase efficiency. This thesis will discuss techniques to improve surface properties of semiconductor photoelctrode materials, namely tin oxide (SnO2) and iron oxide (Fe2O3) for enhancing their functional properties. An anionic surfactant was used to interfacially template tin oxide during electrodeposition, and resulted in crystalline SnO2 with a 3-dimensional, worm-like mesoporous structure. The electrodes were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Nitrogen adsorption (BET), and for photochemical properties (UV-vis/photocurrent). A new anodic electrodeposition route for highly transparent iron oxide films was developed that greatly simplifies the deposition conditions while eliminating complexing agents and toxics. The films were surface treated with aluminum and tin dopant solutions, and the resulting films showed enhanced photoelectrochemical properties. This general surface treatment strategy allows for application to various hematite photoelectrodes, and further, allows for adsorption of Co2+ which has been shows to increase the efficiency of catalytic water oxidation. The increase in photoelectrochemical performance will be discussed using several types of materials and photoelectrochemical studies. Silicon dioxide, or silica (SiO2), is an abundant, robust metal oxide that can be synthesized in various mesoporous forms (films, powders, etc.) with many applications in catalysis, sensing, drug delivery and adsorption. A one-pot synthesis technique was developed to coat mesoporous silicas with polypyrrole (PPy) using a surface acid-catalyzed polymerization technique. The surface acidity of silica (pKa = 4.76) ensures polymerization only on the silica surface, and allows for uniform coating of the entire mesoporous framework. These silica-polymer composite materials were analyzed by a variety of materials characterization techniques, and applications will be discussed