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Titania-based cotton textiles have been prepared by covering the surface of the fabrics with crystalline titania anatase, which is known for its nontoxicity, low cost and for its photocatalytic activity in the degradation of many organic compounds. The coatings were prepared by using the widely used commercial P25 titania (35-65 m2/g), as reference, and an ordered mesoporous titania with high surface area (165 m2/g) prepared by soft template assisted route. In order to promote the interaction between titania and cotton textile, titania-silica nanocomposite coatings have been prepared by dispersing the titania powder into a silica sol used as binder. FE-SEM investigations revealed that the fabrics are uniformly covered by silica-titania coatings and titania particles are partially embedded into silica matrix. The presence of crystalline anatase onto cotton fabrics was confirmed by Raman and XRD measurements and it was observed that the anatase peaks were more pronounced by using mesoporous titania. The self-cleaning performances of the functionalized textiles were investigated by monitoring the discoloration of anthocyanin stains after irradiation with a solar simulator. Our findings reveal that the use of mesostructured titania leads to a more efficient discoloration with respect to the commercial P25 titania, suggesting the importance of the titania textural properties on the photocatalytic activity. The high surface area and the smaller crystallites of ordered mesoporous titania allow to gain a high number of exposed sites that can improve the self-cleaning performances of the functionalized textiles with respect to commercial P25 titania. These results appear promising to further improve the efficiency of self-cleaning cotton fabrics.

(La,Sr)(Co,Fe)O3 (LSCF) perovskites are well known promising materials for cathodes of solid oxide fuel cells. In order to reduce cathode operational temperature, doping on B-sublattice with different metals was suggested. Indeed, as it was shown recently experimentally, doping with low Pd content increases oxygen vacancy concentration which is one of factors controlling oxygen transport in fuel cells. In this Communication, we modeled this material using first principles DFT calculations combined with supercell model. The charge density redistribution, density of states, and local lattice distortion around palladium ions are analyzed and reduction of the vacancy formation energy confirmed.

Study of the photocatalytic activity of Keggin and Wells Dawson heteropolyacids: role of the acidity and of the pseudo-liquid phase regime

The reducibility of Au catalysts on CeO2 supports doped with 1 and 2.5 mass% Y2O3 by two types of preparation methods (impregnation and co-precipitation) has been studied by temperature-programmed reduction and compared with that of pure Au/CeO2. The kinetic parameters of reduction were determined simulating each reduction process. The capacities of these catalysts to retain oxygen have been evaluated by temperature-programmed desorption. The catalytic activities in water gas shift reaction were determined measuring CO conversion between 413 and 623 K. The catalytic performances of all these catalysts were explained in terms of mobility of the oxygen ions of the CeO2 lattice.

In this study, state-of-art La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF) and Ba0.5Sr0.5Co0.8Fe0.2O3-? (BSCF) peroskites were investigated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) and their behaviour under applied overpotential conditions was compared. The effect of wet infiltration by La0.8Sr0.2MnO3-? nano-sized discrete layer on performance and ageing effect was also analysed [1]. Electrochemical impedance spectroscopy (EIS) was applied to the cathode/Ce0.8Sm0.2O2-?- electrolyte system, to study the redox behaviour of the two different electrode phases. A decrease in polarization resistance for both LSCF- and BSCF-infiltrated electrodes was pointed out, compared to the reference ones, at open circuit voltage (OCV). Conversely, the application of cathodic overpotentials (-0.1 to -0.3 V) resulted in opposite effects on LSCF- and BSCF-based cathodes; calculation of the chemical capacitance highlighted a different response of the oxygen vacancies concentration to the applied voltage for the two perovskites compositions

Catalysts of palladium (1 wt%) deposited over silica SBA-15 supported LaMn0.4Fe0.6O3 perovskite (with perovskite loading of 10, 30 and 40 wt%), characterized by several techniques (BET, SAXS, XRD, TPR) are tested in the combustion of methane. Bulk LaMn0.4Fe0.6O3 with the corresponding supported Pd catalyst are also considered for comparison purpose. Dispersing LaMn0.4Fe0.6O3 oxide over silica SBA-15 improves the activity of the supported palladium catalysts to an extent depending on the perovskite loading. After ageing at 600 °C for 14 h, Pd catalysts supported over SBA-15 loaded with 30 and 40 wt% of LaMn0.4Fe0.6O3, deactivate less as compared to Pd over bulk perovskite. Moreover, during catalytic tests carried out in the presence of 10 vol. ppm SO2 these catalysts exhibit better sulphur tolerance and higher regeneration capability as compared to the Pd/LaMn0.4Fe0.6O3. The superior performance of such catalysts is attributed to the good dispersion of the LaMn0.4Fe0.6O3 over the SBA-15, with consequent increase of the perovskite surface area with respect to bulk perovskite. In addition, the porous structure of the silica contributes to a better stabilization of the active species against sintering and acts as a chemical sink during the catalyst exposure to SO2.

Nowadays, optimization of technologies for green energy supply is one of the most important challenges. In this context, solid oxide fuel cells (SOFCs) are valid alternatives for renewable energy production. Doped SrFeO3 have already been studied in the literature as electrodes of fuel cells [1, 2]. In this work, the effect of chemical composition of Cerium and Cobalt doped SrFeO3 was investigated in order to apply them as cathodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). In particular, monophasic Sr1-xCexFe1-yCoyO3-? perovskite-type oxides were synthesized by solution combustion synthesis [3] and then calcined at 1000°C/5h. These materials were carefully characterized by X-ray Diffraction coupled with Rietveld analysis, temperature programmed oxidation and reduction, oxygen chemisorption pulses, N2 adsorption, overpotential and conductivity measurements. Figure 1 shows that Co doping improves the conductivity (a) and decreases the reduction temperature relative to the TPR peaks, considering very similar surface area values (b). Moreover, it was found that the H2 consumption of the first TPR peak is smaller for the perovskite containing more Co, indicating a higher amount of B-site cations with lower oxidation state. Furthermore, it was observed that Ce doping stabilizes the cubic structure of Co-doped SrFeO3, as previously noticed for Ce-doped SrFeO3 without cobalt [1]. On the other hand, the oxygen chemisorption does not seem to be a determining factor for the electrochemical properties of doped SrFeO3. In conclusion, results show that the electrochemical performances of doped SrFeO3 cannot be optimized without investigating the synthesis-composition-structure-properties relationships in these materials.

Highly dispersed gold catalysts supported on different solids have shown high catalytic activity towards many reactions of industrial and environmental importance. When silica is used as a support it is very difficult to obtain an optimal gold dispersion degree due to the low affinity of gold for SiO2. Mesoporous SBA-15, with a highly ordered 2D hexagonal structure and well defined pore size and thicker walls, seems to be an ideal candidate in order to obtain a strong confinement of gold nanoparticles. Several studies demonstrated the addition of an iron component to gold supported catalysts brings a beneficial effect in terms of enhanced activity, selectivity and resistance to deactivation. In our previous works we demonstrated it is possible to synthesize catalysts containing iron stabilized gold nanoparticles with a controlled size and an intimate contact between gold and iron using bimetallic carbonyl clusters as precursors of the active phase. Thus, in the present work we combined the use of SBA-15 and the carbonyl clusters preparation method. Bimetallic iron-gold catalysts were prepared on SBA-15, starting from the bi-metallic carbonyl cluster salt, [NEt4][AuFe4(CO)16], aiming to obtain highly dispersed gold nanoparticles within the pores of SBA-15 and stabilized by an iron layer. Moreover, in order to increase the adsorption and the anchoring of the cluster on the support, SBA-15 surface was functionalised by amino groups through reaction with (3-Aminopropyl)triethoxysilane. Prepared catalysts were characterized and tested in the total oxidation of methanol.

The catalytic performance and the sulphur resistance of a Pd (0.7 wt%) catalyst supported over Co3O4(30 wt%)–CeO2(70 wt%) mixed oxide were investigated in the oxidation of methane under stoichiometric and lean conditions. The catalytic behaviour was compared with that of two reference catalysts, palladium supported over pure Co3O4 and CeO2. Catalysts were characterized by XRD, BET, XPS and FTIR measurements. Regeneration by a CH4-reducing treatment at 600 °C was investigated.

The importance of pure-phase titanium oxide materials as catalysts, sensors, and photonic band-gap materials has been growing steadily. Recently, more attention has been focused on nanostructured titanium oxide showing controlled and periodic porosity on a nanometric scale. The nanocrystal size control of porous nanostructured titanium oxide in an anatase form is a crucial step for the organic template method. Simple template removal by evaporation in an inert atmosphere is reported in this article and compared with the calcination technique usually reported in the literature. The proposed method allows the formation of a double-porous (macro and meso) anatase phase. We demonstrate that it highly preserves the macropore order into a titanium oxide material and induces narrowly dispersed mesopores by controlling the nanocrystal size that is kept around 6 nm. For the proposed method, polystyrene beads are particularly suitable as templates, being evaporated in the temperature range of anatase existence. The final high surface area makes the materials appealing for applications as photocatalysts or sensors.

A series of Au/FeOx/SBA-15 type materials were prepared by two methods: one conventional and one non-conventional: gold deposition-precipitation on FeOx/SBA-15 and bimetallic carbonyl cluster deposition on SBA-15, respectively. Both chemical physical characterization and catalytic activity tests in the complete combustion of methanol show that the new preparation method of Au/FeOx-supported catalysts leads to the anchoring of the Au by modifying the surface of SBA-15 with FeOx species. This effect results in a considerable improvement in catalyst performance as compared to the classic preparation by deposition-precipitation of Au on SBA-15 and FeOx/SBA-15.

The influence of catalyst pre-treatment temperature (650 and 750 °C) and oxygen concentration ( λ = 8 and 1) on the light-off temperature of methane combustion has been investigated over two composite oxides, Co 3 O 4 /CeO 2 and Co 3 O 4 /CeO 2 –ZrO 2 containing 30 wt.% of Co 3 O 4 . The catalytic materials prepared by the co-precipitation method were calcined at 650 °C for 5 h (fresh samples); a portion of them was further treated at 750 °C for 7 h, in a furnace in static air (aged samples). Tests of methane combustion were carried out on fresh and aged catalysts at two different WHSV values (12 000 and 60 000 mL g −1 h −1 ). The catalytic performance of Co 3 O 4 /CeO 2 and Co 3 O 4 /CeO 2 –ZrO 2 were compared with those of two pure Co 3 O 4 oxides, a sample obtained by the precipitation method and a commercial reference. Characterization studies by X-ray diffraction (XRD), BET and temperature-programmed reduction (TPR) show that the catalytic activity is related to the dispersion of crystalline phases, Co 3 O 4 /CeO 2 and Co 3 O 4 /CeO 2 –ZrO 2 as well as to their reducibility. Particular attention was paid to the thermal stability of the Co 3 O 4 phase in the temperature range of 750–800 °C, in both static (in a furnace) and dynamic conditions (continuous flow). The results indicate that the thermal stability of the phase Co 3 O 4 heated up to 800 °C depends on the size of the cobalt oxide crystallites (fresh or aged samples) and on the oxygen content (excess λ = 8, stoichiometric λ = 1) in the reaction mixture. A stabilizing effect due to the presence of ceria or ceria–zirconia against Co 3 O 4 decomposition into CoO was observed. Moreover, the role of ceria and ceria–zirconia is to maintain a good combustion activity of the cobalt composite oxides by dispersing the active phase Co 3 O 4 and by promoting the reduction at low temperature.

An in situ cell for reductive and oxidative treatments at different temperatures that allows the possibility of recording data as a function of temperature has been designed and constructed for X-ray absorption experiments at the GILDA beamline BM08 of ESRF. The cell is linked to a mass quadrupole spectrometer providing control of the reaction gases and monitoring of the products. The apparatus allows measurements to be performed both in transmission and fluorescence geometry. The cell was tested by studying the CO oxidation reaction promoted by a Pt/ceria-zirconia-supported catalyst. The CO(2) yield is correlated with the structural results confirming the existence of a strong metal-support interaction between the Pt metal clusters and the ceria-zirconia support.

Bimetallic Pd-Ag and Pd-Cu pumice-supported catalysts have been synthesized following different preparation procedures with the aim of improving the selectivity and reactivity of monometallic Pd/pumice systems. The structural characterization, carried out by X-ray Diffraction, X-ray Absorption and X-ray Photoelectron Spectroscopy, allowed to investigate the importance of the preparation procedures in the alloy formation.