This paper pursed one new cost effective strategy to improve the photocatalytic activity of the sol-gel developed Zn doped TiO2 by mechano-chemically milling in high energy planetary mill. The results showed that the photocatlytic activity was improved two times due to the increase of the surface area and the decrease in average crystallite size at the same time after using the high energy ball milling. Kubelka-Munk spectra of pristine and ball milled samples revealed a blue shift from 3.2 eV to 3.35 eV, which may be because of the presence of quantum size effects. SEM microstructural investigations revealed variations in the surface morphology with different Zn doping concentrations in the TiO2-Xwt.% Zn nanoparticulates. EDS spectra of these samples confirmed the stoichiometric concentration of Zn. Other characterization including X-ray diffraction (XRD), BET surface and the photocatalytic decomposition were also studied and the results were in agreement with each other.

A system to grow heteroepitaxial thin-films of solid oxide fuel cell (SOFC) cathodes on single crystal substrates was developed. The cathode composition investigated was 20% strontium-doped lanthanum manganite (LSM) grown by pulsed laser deposition (PLD) on single crystal (111) yttria-stabilized zirconia (YSZ) substrates. By combining electrochemical impedance spectroscopy (EIS) with x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy XAS measurements, we conclude that electrically driven cation migration away from the two-phase gas-cathode interface results in improved electrochemical performance. Our results provide support to the premise that the removal of surface passivating phases containing Sr2+ and Mn2+, which readily form at elevated temperatures even in O2 atmospheric pressures, is responsible for the improved cathodic performance upon application of a bias.

The rate law for CO oxidation over Pd-substituted BaCeO3 was studied. Under CO-rich conditions over a range of pressures and temperatures, changing reaction orders for both CO and O2 suggest the coexistence of both Langmuir-Hinshelwood and BaCeO3-mediated mechanisms. The latter dominates at high P(CO)/P(O2), while both mechanisms contribute significantly at low P(CO)/P(O2). Under CO-lean conditions, the Langmuir-Hinshelwood mechanism dominates the kinetics. The importance of the BaCeO3-mediated mechanism increases with temperature. Steady-state isotopic transient kinetic analysis (SSITKA) using 18O2 confirmed the participation of labile lattice oxygen, thus BaCeO3 behaves as a BaO-stabilized form of CeO2.

Low temperature CO oxidation is characterized by slow reaction kinetics and CO self-poisoning of the catalyst, which compete with each other. A platinum catalyst with ceria as a promoter supported on a high surface area silica support has been developed. The catalyst has a significant activity for CO oxidation even in the presence of moisture. The catalyst showed a significant increase in activity with decreasing particle size (η<0.95, even at 100μm), indicating a clear transport limitation.

In case of larger catalyst particles the diffusional resistances affect the reaction kinetics, leading to greater rates of CO self-poisoning causing deactivation of the catalysts. However, conventional packed bed of smaller particles poses problems such as high pressure drop, packing issues, bed channeling, flow maldistributions, and dead zones in the reactor bed, which result in poor inter-phase heat and mass transfer rates. Most of these problems are related to poor packaging of smaller particles, strongly suggesting the need for immobilization of small particles. A new class of micro-structured materials consisting of sorbents/catalysts entrapped in metal, ceramic, or polymer microfibers (MFES/MFEC) has been developed at Auburn University. These materials immobilize the small particles by sinter-locking them in fiber mesh. The immobilization of particles results in better heterogeneous contacting efficiency. Additional studies have shown that the high voidages and structural uniformity of the MFES lowered the flow maldistributions, eliminated the peaking flows between particles, and helped achieve better radial dispersion. Thus MFEC/MFES improved inter-phase transport rates.

The Pt-CeO2/SiO2 catalyst entrapped in metal microfibers demonstrated a significant improvement in CO conversion compared to a conventional packed bed configuration while maintaining a lower pressure drop. Further catalyst entrapment in metal microfibers minimized cold spots in the reactor bed due to better intra-phase heat transfer rate. Higher effective thermal conductivity of MFEC improved the activity of the catalyst, which was particularly visible at high CO concentration wherein the CO inhibition kinetics takes over. For example, MFEC with 1/3 rd of catalyst loading as that of packed bed of same particle size, outperformed packed bed configuration.

The catalysts were prepared by incipient wet impregnation. Surface characterization of catalysts was carried out using CO, H2, O2 chemisorption, O2 – H2 titration, N2 physisorption, powder XRD, and was correlated with catalytic activity.

This microfibrous entrapped catalyst demonstrated a great potential for low temperature CO oxidation. These MFEC can be used in air purification, emergency escape products, and as a cathode air filter for PEM fuel cells.

Brominated aromatic compounds have been widely used in synthetic organic chemistry for themanufacturing of many bulk and fine chemicals. In contrast to direct bromination by toxic elemental bromine or HBr, we developed an environmentally friendly system for oxybromination using hydrogen peroxide and ammonium bromide in the aqueous phase under mild temperature and near neutral conditions over a SBA-15 supported sulfated zirconia (SZ) catalyst. The ready availability of the catalyst and the nearly neutral aqueous solution are the salutary features of this approach. Bromination of aromatics with electron-withdrawing group took place readily, and bromoproducts were produced in moderate to excellent yields. A good to excellent para-selectivity was observed. The SZ/SBA-15 catalyst may be re-used several times without substantial loss of activity.

We also studied the catalytic activity of SZ which were supported on mesoporous SBA-15 silica or mesoporous SZ. On bromination silica supported sulfated zirconia (SZ/SBA-15) showed much better catalytic ability for bromination then self-supported SZ (m-SZ). Furthermore, we found the catalytic activity of SZ decreased as the calcinations temperature increased. The good catalytic performance of the SZ/SBA-15 materials was attributed to the well dispersed of sulfate groups to give sulfated silica-zirconia of with (1) very good redox property and (2) high strength and high density of acid sites.

Gold nanoparticles were linked to ZnO films and nanowires using phosphonic and carboxylic acid ligands. TEM and STEM-HAADF characterization showed that gold nanoparticles modified with both types of ligands anchored on ZnO nanowire surfaces as well as on ZnO films. After removing the ligands from the interface between ZnO nanowires and supported gold nanoparticles, the electric conductivity in the presence of methanol vapor increased by 100 times as compared to the bare ZnO nanowire, which suggested enhanced-catalytic effects due to the hybrid structure. In addition, ZnO/Au nanomaterials were synthesized by linking ZnO nanoparticles and carboxylate-functionalized gold nanoparticles in solution. UV-vis characterization showed both the bandgap absorption from ZnO and the plasmon absorption from gold nanoparticles. Formation of hybrid nanosystems like these using organic ligands as linkers not only can lead to materials with enhanced properties but also minimize the waste of precious elements because the assembly process is an additive, rather than subtractive, process.

Fusion of metallic nanoparticles at both surfaces of silica colloids and nanoporous bulk materials has been utilized as an effective method to integrate inorganic and organic components into nanocomposite materials. When performed on substrates that have been modified with hydrophobic functional groups, aminosilica colloids doped with metallic nanoparticles through the ethylenediamine functional groups adhere to the substrates and self-assemble into nanocomposite film with its thickness to be the function of the time. On the contrary, without metal-bound functional groups, fusion of metallic nanoparticles can be induced at the interface of nanoporous silica when polymer is utilized as the mobile phase for metal nanoparticles inside of silica. Formation, mobilization, and fusion of metallic nanoparticles within the polymer phase can be simultaneously induced at 160 ˚C, during which reactions alter the physical appearance of the materials from transparent to silver metallic color. These two methods can combine with soft-lithography method to create functional structures that exhibit enhanced electrochemical property.

In the last decades, HRTEM approach has been quite fruitful to study structural characteristics of layered transition metal sulfide (LTMS) catalytic materials since providing direct local information about the structural organization of this quite important class of catalysts at the nanoscale level. However, up to now, HRTEM observations of some common localized structural organization like honeycomb-like structures have remained unexplained. In the present study, a structural model corresponding to stacked 2H-MoS2 slabs twisted along their basal direction is proposed to explain honeycomb like-structures observed by HRTEM. This model is based on a comparison between experimental and simulated images of 2H-MoS2 catalysts promoted with cobalt. The resulting Density of States (DOS) of the twisted structure was then calculated.

Water soluble poly(4-styrenesulfonic acid-co-maleic acid), PSSA-co-MA, stabilized nickel(0) and cobalt(0) nanoclusters were prepared for the first time from the reduction of nickel(II) chloride and cobalt(II) chloride by using minimum amount of sodium borohydride shortly before their usage as catalysts in the hydrolysis of ammonia-borane (AB) in the same medium at room temperature. PSSA-co-MA stabilized nickel(0) and cobalt(0) nanoclusters showed high catalytic activity in hydrogen generation from the hydrolysis of AB even at low temperature.

Platinum nanoparticles were dispersed in mesopores of mesoporous silica using a sol-gel process with a composite template consisting of an amphiphilic triblock copolymer (Pluronic P123 or F127) and a Pt-organic complex, which was prepared with K2Pt(II)Cl4 as a Pt source and 1,10-phenanthroline as a chelating agent. The obtained Pt-1,10-phenanthroline complex did not dissolve in any of several solvents, e.g., hexane, benzene, toluene, THF, H2O, CH3OH, and C2H5OH. However, when the Pt-1,10-phenanthroline complex was reacted with ethylenediamine it dissolved in many solvents. Platinum nanoparticles dispersed in mesoporous silica were obtained using a sol-gel process with a complex template consisting of Pt-1,10-phenanthroline-ethylenediamine, and an amphiphilic triblock copolymer (Pluronic P123 or F127). A sample dried at 353 K was bright yellow. When it was subsequently heat-treated at 823 K, it turned light gray. This change indicates that Pt nanoparticles can be obtained by heat-treatment at high temperature, because, to generate Pt nanoparticles, the organics chelated to Pt ions must be removed. Measurements from small-angle x-ray scattering show that mesoporous silica obtained using a complex template has a much more highly ordered pore structure than that obtained using only an amphiphilic triblock copolymer. It has both large pores (above 8 nm) and a large surface area (about 290 m2/g). Furthermore, results of a TEM investigation showed that Pt nanoparticles were generated only in mesopores of mesoporous silica.

Pd-Fe alloys have attracted attention in PEM fuel cell research because they were found to be comparable to Pt electrocatalysts in oxygen reduction reaction (ORR) kinetics at the cathode. In this study, the surface morphology of a Pd3Fe(111) single-crystal sample and oxygen reaction on the surface were investigated by low energy electron diffraction (LEED), low energy ion scattering (LEIS), x-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. Strong segregation of Pd atoms was observed after annealing in UHV. Particularly, Pd single adatoms and dimers were found on the surface after high temperature annealing, which differs from most other well-studied binary alloy systems. Low free energy of Pd, strain relaxation, and interaction between Pd and Fe, are potentially responsible for the formation of this unusual surface. Adsorption of oxygen reversed the segregation trend and oxidized surface Fe. Ordered surface phases were observed after oxygen exposures at elevated temperatures. The reducing activity of Fe atoms in the alloy inhibited Pd oxidation, and weakened Pd-O interactions on Pd3Fe(111) are consistent with enhanced ORR kinetics.

We have investigated the effect of N doping into Cu2O films deposited by reactive magnetron sputtering. With increasing N-doping concentration up to 3 at.%, the optical bandgap energy is enlarged from ˜2.1 to ˜2.5 eV with retaining p-type conductivity as determined by optical absorption and Hall-effect measurements. Additionally, photoelectron spectroscopy in air measurements shows an increase in the valence and conduction band shifts with N doping. These experimental results demonstrate possible optical bandgap widening of p-type N-doped Cu2O films, which is a phenomenon that is probably associated with significant structural changes induced by N doping, as suggested from x-ray diffraction measurements.

Platinum (Pt) nanoparticles were prepared on a glassy carbon plate by a sputtering method and then irradiated with proton (H+) beams at energies of 0.38 and 10 MeV at room temperature. Cyclic voltammetry in an aqueous 0.5 mol/dm3 H2SO4 solution suggested that the lower-energy beam irradiation enhanced the active surface area of the Pt nanoparticles, calculated from the coulombic charge for hydrogen desorption. Thus, the nanoparticles would be modified by H+ beam-induced electronic excitation so that they have higher surface activity. The mechanism of this irradiation effect seems to be rather complicated and is still unclear at present, but we may discuss it in relation to a change in the interfacial crystal structure during the irradiation.

Mesoporous silica materials have received much interest due to commercial applications in chemical separations and heterogeneous catalysis. Recent studies have reported via a sol-gel nanocasting technique, monolithic mesoporous silica with wormlike pore framework could be prepared by utilizing room-temperature ionic liquids (RTILs) as templates and solvents. Although previous reports have indicated that the wormlike pores would be formed in the silica, the detailed pore network structure still remained the crucial issues to be resolved. In the present study, we investigated the pore structure in the monolithic mesoporous silica, which was templated by RTIL (1-butyl-3-methyl-imidazolium-tetrafluoroborate). We revealed an open fractal pore network with a branched and self-similar appearance was formed by the aggregation of the individual spherical pores. Transmission electron microscopy micrographs displayed that the disordered wormlike pore framework was formed in the silica. Furthermore, the small angle X-ray scattering profile measured herein further exhibited three distinct regions of power-law scattering on the respective length scales. In the high-q region, the profile followed Power behavior and a power-law of -4 was observed for the surface fractal dimension of 2, manifesting the primary pore with a smooth surface and a spherical appearance. In the intermediate-q region, a power-law of -2.5 (mass fractal dimension of 2.5), indicating an open mass fractal network was formed by the aggregation of the individual primary pores. Moreover in the low-q region, the power-law of -4 was observed for mass-fractal agglomerates of aggregates. With the proceeding analysis of unified equation in terms of two structural levels, the radiuses of gyration of primary pore (Rg1)and its aggregates (Rg2) were fitted as ca. 0.9 nm and 5.5 nm, respectively. For a spherical-model pore, the radius of pore (R) was ca. 1.16 nm; thus, the averaged pore diameter (D) was 2.32 nm. The number of primary pores in a fractal aggregate (degree of aggregation, z) was calculated as ca. 67.

ZnO nanostructured films were deposited at room temperature on glass substrates and cotton fabrics by activated reactive evaporation in a single step without using metal catalyst or templates. Morphological observation has shown that the nanostructured film contains seaurchin-like structures, and this seaurchin containing large number of randomly grown ZnO nanoneedles. Microstructural analysis revealed the single crystalline nature of the grown nanoneedles and their growth direction was indentified to be along [0002]. PL spectrum of nanostructured films has shown a relatively weak near-band-edge emission peak at 380 nm, and a significant broad peak at 557 nm due to the oxygen vacancy-related emission. ZnO nanostructured films grown on glass substrates and cotton fabrics have shown good photocatalytic activity against rhodamine B.

Platinum nanoparticles stabilized by linear polyethyleneimine were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The particle sizes were 3.26 nm and 1.76 nm when the molecular weights of linear polyethyleneimine were 25000 and 2150, respectively. These nanoparticles were well-dispersed in water in the range of pH 1-6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the range of pH 0-8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the range of pH 0-10. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group.

This paper investigated an inexpensive way to improve the overall photocatalytic activity of TiO2 by N- doping using anhydrous ammonia as the nitrogen source. Doping amount could be further optimized by controlling the reaction time. Experiments showed that photocatalytic effect has one threshold concentration. Lower or higher reaction will decrease the photocatalytic efficiency. Experiments showed that the suitable reaction temperature should be lower than 650oC.

Nanostructured hematite thin film for photoelectrochemical (PEC) splitting of water has great potential in the design of low-cost, environmental friendly solar-hydrogen production. Presently, solar-to-hydrogen conversion efficiency of PEC cell using iron oxide is limited by its poor charge transport due to high recombination losses and mismatch of band edges position with the redox level of water. High energy heavy ion irradiation provides the researchers a new dimension to introduce the desired changes in the behaviour of the material, which largely influence their properties. In order to get efficient PEC system, spray-pyrolytically deposited nanostructured hematite thin films were modified by irradiating the samples with 120 MeV Ag9+ ions with fluences ranging from 5×1011 to 1×1013 ions/cm2. Irradiated samples exhibited a partial transition from the hematite to the magnetite phase and reduction in particle size as indicated by XRD and Raman analysis. SEM picture showed a decrease the thickness and porosity of the films after irradiation. These irradiated films, when used in PEC cell showed significantly higher photocurrent density than unirradiated α-Fe2O3.

Low temperature oxidation of NiAl(110) alloy has been studied with surface characterization methods and cross-section TEM. Our work demonstrated thin and high quality single crystal γ-Al2O3(111) films have grown heteroepitaxially on NiAl(110) alloy. The orientation relationship of metal/oxide is NiAl(110) || γ-A12O3(111)and NiAl(211)∥γ-Al2O3(311) with very slight lattice mismatch. Al cation outward diffusion dominates during this low temperature oxidation confirmed by EELS mapping along interface.

The Cu-type and (Cu-Fe)-type film catalysts have been successfully prepared by the electroless plating on ZnO nanorods/stainless steel substrates. The microstructure features of the (Cu-Fe)-type films are high porosity and plate-type grains. The addition of iron into Cu-type film can improve the reducibility and the stability of the film catalysts. The reduction temperature of the (Cu-Fe)-type film catalysts decreases with increasing the addition of Fe. For Cu-5 at% Fe film, the reduction temperature is in the range of 195°C to 216°C as comparison in the range of 208°C to 233°C of the Cu-type film catalysts.