TiO2, TiO2-1at.% W and TiO2-1at.% Cr were produced from metal-organic precursors by flame spray synthesis (FSS). TiO2-0.5at.% N was obtained by ammonolysis of FSS made TiO2 nanopowder in a rotating tube furnace under NH3 atmosphere. According to the X-ray diffraction (XRD) analysis, anatase is the predominant phase in all samples. Diffusive reflectance and the resulting band gap energy (Eg) were determined by diffusive reflection spectroscopy (DRS). Additional impurity bands at 2.43 and 2.57 eV for N- and Cr-doped TiO2, respectively have been observed. The impurity band formed in the band gap resulted in increase of the light absorption in the visible range. The photocatalytic performance of the nanopowders under ultraviolet (UV, 290-410 nm) and visible light irradiation (Vis, 400-500 nm) was studied by the degradation of methylene blue (MB) in aqueous suspensions. It was found that all types of dopants influence the structure, interaction with the visible light as well as photocatalytic activity. Among all nanopowders, TiO2-W exhibited the best photoactivity, much higher than the commercial TiO2-P25 nanopowder. The optimum of the photodecolourization was obtained for 0.7 and 1 at.% W.

Microcomposites composed of titanium dioxide nanoparticles embedded within cross-linked, thermally responsive microgels of poly(N-isopropylacrylamide) were prepared. These microcomposites showed rapid sedimentation, which is useful for gravity separation of the titania nanoparticles in applications such as environmental remediation. To investigate the degradation kinetics using these microcomposites in aqueous suspensions, methyl orange was employed as a model contaminant. The decline in the methyl orange concentration was monitored using UV-Vis spectroscopy. Degradation of methyl orange was also measured using only nanoparticles TiO2 (DegussaTM P25) for comparison with the microcomposites. Experiments were performed at different pH conditions that spanned acidic, neutral, and basic conditions to gain insight into the interplay of TiO2 surface charge, ionization of the polyelctrolyte chains in the microcomposites, and ionization of the methyl orange.

We report on an integrated photoelectrochemical (PEC) device for hydrogen production using amorphous silicon carbide (a-SiC:H) material as the photoelectrode in conjunction with an amorphous silicon (a-Si:H) tandem photovoltaic device. With the use of a-Si:H tandem solar cell, the flat-band potential of the hybrid PEC structure shifts significantly below the H2O/O2 half-reaction potential and is in an appropriate position to facilitate water splitting. Under reverse bias, saturated photocurrent of the hybrid device ranges between 3 to 5 mA/cm2 under AM1.5 light intensity. In a two-electrode setup (with ruthenium oxide counter electrode), which is analogous to a real PEC configuration, the hybrid cell produces photocurrent of about 0.83 mA/cm2at zero bias and hydrogen production is observed. The hybrid device exhibits good durability in pH2 buffered electrolyte for up to 150 hours (so far tested).

We report on the development of tungsten-oxide-based photoelectrochemical (PEC) water-splitting electrodes using surface modification techniques. The effect of molybdenum incorporation into the WO3 bulk or the surface region of the film is discussed. Our data indicate that Mo incorporation in the entire film (WO3:Mo) results in poor PEC performances, most likely due to defects that trap photo-generated charge carriers. However, compared to a pure WO3 (WO3:Mo)-based PEC electrode, a 20% (100%) increase of the photocurrent density at 1.6 V vs. SCE is observed if the Mo incorporation is limited to the near-surface region of the WO3 film. The resulting WO3:Mo/WO3 bilayer structure is formed by epitaxial growth of the WO3:Mo top layer on the WO3 bottom layer, which allows an optimization of the electronic structure induced by Mo incorporation while maintaining good crystallographic properties.

Electronic structure properties of a photo-catalyst slab system based on a material YVO4 or InVO4 which is sandwiched by water molecular layers have been investigated by first-principles calculation. As a result, we found the tendency that the band gap of the InVO4 slab system sandwiched by water molecular layers was smaller than that of YVO4 system while the band gap values of the bulk crystals of YVO4 and InVO4 are almost same. This result may provide us a good clue to understand the reason why the InVO4 system can indicate a visible light response in photo-catalysis and the YVO4 system can not.

Photoelectrochemical (PEC) hydrogen production, using sunlight to split water, is an important enabling technology for a future “Green” economy which will rely, in part, on hydrogen as an energy currency. The traditional semiconductor-based PEC material systems studied to date, however, have been unable to meet all the performance, durability and cost requirements for practical hydrogen production. Technology-enabling breakthroughs are needed in the development of new, advanced materials systems, and toward this end, the U.S. Department of Energy’s Working Group on PEC Hydrogen Production is bringing together experts in analysis, theory, synthesis and characterization from the academic, industry and national-laboratory research sectors. Key Working Group activities, as described in this paper, include performing techno-economic analyses of large-scale PEC production systems and establishing standardized testing and screening protocols for candidate PEC materials systems. In addition, a number of Working Group “Task Forces” are focused on advancing critical PEC materials theory, synthesis and characterization capabilities for application in the research and development of broad-ranging materials systems of promise, including complex metal-oxide and -nitride compounds, amorphous silicon alloys, III-V semiconductors and the copper chalcopyrites. The current status of Working Group activities and progress is summarized.

Traditional techniques to remove contaminants (carbon adsorption, incineration, biological activity and chemical treatment) have a lot of disadvantages. Advanced Oxidation Processes (AOP’s) are used as alternative processes in the degradation of surfactants and in general for wastewater treatment. They are based on the generation of OH•, one of the most powerful oxidant known (E° = 2.73 V) and capable to react non-selectively with any organic compound. In the present work, the degradation of a cationic surfactant (dodecylpyridinium chloride (DPC)) was performed. The photodegradation reaction was investigated both in a slurry reactor and in a vessel where the photocatalyst (P25 by Degussa) was anchored onto an aluminum surface to avoid the final filtration of the powder at the end of the reaction. Moreover a new photoreactor was built on purpose to investigate the influence of the pressure on the degradation process.

There is a real need for a material which absorbs in the visible light of the solar spectrum, is stable in water and at the same time economical. One-dimensional vertically aligned nanotubes have contributed to a great extent towards the visible light driven photoelectrolysis of water. In this work, we give an overview of the different nanotubes obtained through anodization of various metals and their application in the photooxidation of water

This project focuses on using indium oxide and indium iron oxide as an alloy to make a protective thin film (transparent, conductive, and corrosion resistant or TCCR) for amorphous silicon based solar cells, which are used in immersion-type photoelectrochemical cells for hydrogen production. From the work completed, the results indicate that samples made at 250 °C with 30 Watt of indium and 100 Watt of indium iron oxide, and a sputter deposition time of ninety minutes produced optimal results when deposited directly on single junction amorphous silicon solar cells. At 0.65 Volts, the best sample displays a maximum current density of 21.4 mA/cm2.

Visible-light-driven Ag3VO4 photocatalysts were successfully synthesized using low-temperature hydrothermal synthesis method. Under various hydrothermal conditions, the structures of silver vanadates were tuned by manipulating the hydrothermal time and the ratio of silver to vanadium. X-ray diffraction (XRD) results reveal that the powders prepared in a stoichiometric ratio consisted of pure α-Ag3VO4 or mixed phases of Ag4V2O7 and α-Ag3VO4. With increasing the Ag-to-V mole ratio to 6:1, the resulting samples were identified as pure monoclinic structure α-Ag3VO4. UV-vis spectroscopy indicated that silver vanadate particles had strong visible light absorption with associated band gaps in the range of 2.2-2.5 eV. The sample synthesized in the excess silver exhibited higher photocatalytic activity than that synthesized in a stoichiometric ratio. The powder synthesized at silver-rich at 140℃ for 4 h (SHT4) exhibited the highest photocatalytic activity among all samples. The reactivity of SHT4 (surface area, 3.52 m2 g-1) on the decomposition of gaseous benzene was about 16 times higher than that of P25 (surface area, 49.04 m2 g-1) under visible light irradiation. A well developed crystallinity of Ag3VO4 of SHT 4 was considered to enhance the photocatalytic efficiency.

In this study, we can successfully synthesize nano-perovskites, including nano-CaTiO3, nano-SrTiO3, and nano-BaTiO3, by a co-precipitation method. The band gap of the nano-perovskites are 3.65 eV, 3.44 eV, and 3.35 eV, for nano-CaTiO3, nano-SrTiO3, and nano- BaTiO3, respectively. The ability of photocatalysis for nano-BaTiO3 is a little bit better than other nano-perovskites. It is also observed the photocatalytic activity increases with the increasing amount of photocatalysts. Moreover, the ability of photocatalysis using a higher energy UV-light is not promoted with the low energy UV-light.

We report investigation of effect of conduction band edge on the dye injection and transport by preparation of (Ti,Sn)O2 solid mixtures in ratios of 80:20 and 90:10 as possible applications in dye sensitized solar cells. SEM micrographs showed highly porous with nanometer sized particles of around 6 - 10μm diameter. X-ray diffraction patterns showed strong TiO2 anatase peaks with crystal orientation directions (101) being the strongest in both the solid mixtures and in pure TiO2. XPS studies have shown an apparent chemical shift for Ti 2p and O1s core level spectra with an energy difference between the unmodified and the solid mixture being 0.65eV. Initial I-V studies have shown high Voc but low short circuit photocurrent, showing a possible unfavorable band edge shift between the semiconductor and the dye LUMO level.

The R & D developments in several aspects of catalysis area require cleaner and clean up technologies. Catalysts are used for energy conversion and to convert environmentally hazardous materials into harmless compounds. This presentation reviews the work currently under exploration at IICT that illustrates the perspective of photocatalyst technologies for solving energy and environmental issues for providing sustainable development. Studies on development of photocatalytic materials for degradation of phenolic wastes, common industrial effluent, H-acid, Calmagite (an azodye), Isopruturon (herbicide) and for E-coli disinfection are highlighted. Materials like Natrotantite, Ce-modified zeolites, Ag2O/TiO2, CuO/TiO2 and C,N-doped TiO2 are designed and evaluated for photocatalytic splitting of water for generation of hydrogen energy. Furthermore, potential applications of photo catalysts in the chemical synthesis of N-containing heterocyclic compounds like pyrazines and piperazines which are useful intermediates in the synthesis of various drugs, perfumes, herbicides and dyes are new interesting aspects in the presentation. Thus the present review describes the emerging trends in using photocatalysts for energy and environmental applications.

TiO2 anatase nanotubes synthesised via anodic oxidation were used as adsorbent for the uptake of U and Pb from aqueous solution and the photoremoval of As(III). An X-ray photoelectron spectroscopy study of the sorbent medium surface revealed a high adsorption of U and Pb at pH 8. The adsorption of the uranyl ion was enhanced in an anoxy (N2) atmosphere, because this prevents the formation of very stable carbonyl complexes. As(III) was adsorbed on TiO2 but in the presence of O2 and UV light was oxidized to As(V). XPS analysis revealed that in the pH range 3-9 As(V) was always the major species detected at the surface of the titania photocatalyst.

This study investigates bactericidal activities of dental porcelain contained silver/cerium/titania against streptococcus mutans in different irradiations, then the effect of modified titanium dioxide on rheological behavior of dental porcelain slurries is studied for rapid prototyping applications. The results show that the silver/cerium/titania has much higher antibacterial efficiency than that of pure TiO2 either in the room light or under the dark. It is potential to apply this photocatalyst in the dental materials for preventing human teeth from caries because the oral cavity is mostly under dark, partly in the visible light. The modified titanium dioxide not only has a antibacterial effect, but also can improve the rheological behavior of dental porcelain slurries for rapid prototyping applications.