The emergence of hydrogen and fuel cell technologies in transportation and stationary power sectors offers the world important and potentially transformative environmental and energy security benefits. In recent years, research supported by the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Office has contributed substantially to the development of these technologies. Enhanced performance and reduced cost in automotive fuel cells are important examples of achievement. The research investments are clearly paying off, as commercial fuel-cell electric vehicles (FCEVs) are being rolled out by major car manufacturers today. With increasing market penetration of FCEVs, enabling technologies for the affordable and widespread production, storage and delivery of renewable hydrogen are becoming increasingly important. Long term commercial viability of hydrogen and fuel cells in the commercial marketplace will rely on continued materials research on several important fronts. Examples include the discovery and development of: (1) non-platinum-group-metal catalysts for next-generation fuel cells; (2) durable, high-performance photocatalytic materials systems for direct solar water splitting; (3) advanced materials-based systems for low-pressure, high-volumetric-density hydrogen storage; and (4) low-cost, hydrogen-compatible pipeline materials for hydrogen delivery and distribution. Research innovations in macro-, meso- and nano-scale materials are all needed for pushing forward the state-of-the-art in these areas. New approaches in accelerated materials development facilitated by a national Energy Materials Network of advanced scientific resources in theory, computation and experimentation are being adopted at DOE. Application of these approaches to address the key materials challenges in hydrogen and fuel cell technologies are discussed.

The present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

The paper presents the research results of formation features of nanoporous titanium oxide structure under electrochemical anodizing by AC-DC current. It is shown that addition of current AC-component (at the frequency of 100 Hz – 10 kHz) leads to increase of the coating formation rate and to structure quality changes of nanoporous TiO2 coatings: open intertubular space appears, intertubular bridges are formed and the nanotubes section form becomes round.

Thin films of TiO2/SnO2:F multilayers were prepared by spray pyrolysis technique on glass substrate. The samples were prepared using titanium (IV) isopropoxide 98%, ammonium fluoride and tin(II) chloride dehydrate extra pure as precursor materials. Thus, a TiO2 thickness dependence optical study of TiO2/SnO2:F/glass system is presented. The optical property was characterized by UV-Visible transmittance spectroscopy. For all the samples, the average transmissions in the visible wavelength region (400-800 nm) were between 69 and 84%. The optical parameters, such as the real part dielectric function ε1 and the imaginary part dielectric function ε2, of TiO2 and SnO2:F in the TiO2/SnO2:F thin films structure, determined by fitting the measured optical transmittance spectra, are presented and analyzed. Among the various classical dispersion relations for the dielectric function, the Drude model combined with the Lorentzian oscillators was used to get a good fit of transmittance in the measured spectral range. Results on related parameters such as high frequency dielectric constant, plasma frequency, film thickness and band gap are presented.

Niobium-doped TiO2 films as highly transparent conducting oxidic electrodes were prepared by reactive magnetron sputtering from a titanium target in an argon-oxygen gas flow. As-deposited films were amorphous and exhibited high resistivities ranging from 10 to 1×105 Ω cm in dependence on the deposition parameters. We stabilized the reactive magnetron sputtering deposition by adjusting the magnetron discharge voltage at a constant oxygen gas flow. The precise process control during the preparation of the as-deposited films was essential to gain low resistivities (10-3 Ω cm) and low optical absorption coefficients (α550nm < 2×103 cm-1) after annealing. These polycrystalline TiO2:Nb films on borosilicate glass show a quite high electron concentration > 1×1020 cm-3 and a high carrier mobility (≈ 8 cm2 V-1 s-1).

A variety of Titanium dioxide (TiO2) phases and nanostructures have been explored for their applications in photoelectrochemical cells (PECs) for solar-driven water splitting. In this case, anatase phase and TiO2 nanotubes offer significant advantages especially for PEC-based applications. Though, significant efforts have already been engaged to combine the advantages from both the fields, poor activation and the high electron-hole pair recombination rate of TiO2 electrodes, originating from intrinsic physicochemical properties, limits its practical use. As an alternative, we report directly grown TiO2 nanotubes (synthesized on Fluorine doped Tin Oxide (FTO) via facile electrospinning technique) on carbon nanofibers, using hydrothermal method. The hierarchical branch type configuration has an intimate contact between the TiO2 nanotube and carbon nanofiber backbone and offers higher photocatalytic activity than their respective individual components (namely TiO2 nanotubes and carbon nanostructures).

Titania nanotubes were prepared by anodic oxidation of Ti. The titania surfaces were partially coated with Zn by reacting zinc acetate with the nanotubes and then annealed. [1] An annealed nanotube cluster was placed carefully on a silicon wafer using tweezers. Secondary electron images were acquired by bombarding with Cs+ and observing the ejected OZn- and OTi- respectively. The SIMS analysis was done in ultra-high vacuum (∼ 10-10 Torr). The location of before and after the SIMS analysis was confirmed by scanning electron microscopy (SEM). Specific areas with various orientations (vertical and horizontal orientations) of the nanotubes were selected for the NanoSIMS 50L analysis. The NanoSIMS 50L is made by Ametek Cameca, Gennevillieres, France and is capable of doing in situ isotopic analysis of surfaces at high spatial resolution (25 nm2). The average ZnO/TiO was ∼1.8%, confirming the actual content of Zn used during synthesis of the nanotubes. Qualitatively, the TiO/ZnO ratio increased with increasing depth implying that ZnO concentration was decreasing as we probed into the nanotubes.

A facile technique was adopted to synthesize beautiful lilac bush resembling TiO2-SnO2 microflowers aggregates for photodegradation of Congo Red (CR). The TiO2-SnO2 microflowers in the 2-3 μm range with high surface area (80 m2/g), under optimized conditions of catalyst dosage (0.3 g/L), dye concentration (100 ppm) and pH value is 10, exhibit excellent photocatalytic activity under visible light, whereby, 98.3% of the CR aqueous solution was degraded in 40 min of illumination time and also shows good recyclable photocatalytic activities. Further, the gas sensing properties of the as-synthesized material were evaluated towards detection of a variety of volatile organic compounds, such as acetone, methanol, benzene, ammonia, toluene, diethyl ether, and ethanol.

The paper presents the research results of formation peculiarities of barrier electrically insulated coatings based on titanium oxide (TiO2) under conditions of AC-DC electrochemical anodizing. It is shown that overlapping of AC component (at the frequency of 100 kHz – 10 MHz) leads to formation of coatings 1.2-1.4 times thicker. Dependences of the coating thickness on frequency under various ratios of the AC-component amplitude to the DC-component of anodizing voltage have been obtained.

Self-assembled TiO2 foam-like films, were grown by the water based Streaming Process for Electrodeless Electrochemical Deposition (SPEED). The morphology of the ∼1 µm thick films consists of a tangled ropy structure with individual strands of ∼200 nm diameter and open pores of 0.1 to 3 micron dimensions. Such films are advantageous for proposed perovskite solar cell comprising CH3NH3PbI3 absorber with additional inorganic films as contact and conduction layers, all deposited by SPEED. Lateral film resistivity is in the range 20 – 200 kΩ-cm, increasing with growth temperature, while sheet resistance is in the range 2 – 20 x 108 Ω/Sq. X-ray diffraction confirms presence of TiO2 crystals of orthorhombic class (Brookite). UV-vis spectroscopy shows high transmission below the expected 3.2 eV TiO2 bandgap. Transmittance increases with growth temperature.