The interaction between CeO₂-GO or CeO₂-rGO and gold as co-catalysts were here investigated for solar H₂ production by photoreforming of glycerol. The materials were prepared by a solar photoreduction/deposition method, where in addition to the activation of CeO₂ the excited electrons were able to reduce the gold precursor to metallic gold and the GO into rGO. The presence of gold was fundamental to boost the H₂ production, whereas the GO or the rGO extended the visible-light activity of cerium oxide (as confirmed by UV-DRS). Furthermore, the strong interaction between CeO₂ and Au (verified by XPS and TEM) led to good stability of the CeO₂-rGO-Au sample with the evolved H₂ that increased during five consecutive runs of glycerol photoreforming. This catalytic behaviour was ascribed to the progressive reduction of GO into rGO, as shown by Raman measurements of the photocatalytic runs. The good charge carrier separation obtained with the CeO₂-rGO-Au system allowed the simultaneous production of H₂ and reduction of GO in the course of the photoreforming reaction. These peculiar features exhibited by these unconventional photocatalysts are promising to propose new solar-light-driven photocatalysts for green hydrogen production.

Novel yttrium-doped CeO₂, MnO_x, and CeMnO_x composites are investigated as catalysts for low-temperature NH₃-SCR. The study involves the preparation of unmodified oxide supports using a citrate method followed by modification with Y (2 wt.%) using two approaches, including the one-pot citrate method and incipient wetness impregnation of undoped oxides. The NH₃-SCR reaction is studied in a fixed-bed quartz reactor to test the ability of the prepared catalysts in NO reduction. The gas reaction mixture consists of 800 ppm NO, 800 ppm NH₃, 10 vol.% O₂, and He as a balance gas at a WHSV of 25,000 mL g⁻¹ h⁻¹. The results indicate that undoped CeMnO_x mixed oxide exhibits significantly higher deNO_x performance compared with undoped and Y-doped MnO_x and CeO₂ catalysts. Indeed, yttrium presence in CeMnO_x promotes the competitive NH₃-SCO reaction, reducing the amount of NH₃ available for NO reduction and lowering the catalyst activity. Furthermore, the physical-chemical properties of the prepared catalysts are studied using nitrogen adsorption/desorption, XRD, Raman spectroscopy, temperature-programmed reduction with hydrogen, and temperature-programmed desorption of ammonia. This study presents a promising approach to enhancing the performance of NH₃-SCR catalysts at low temperatures that can have significant implications for reducing NO emissions.

In the present study CeO₂, MnO₂ and CeMnO_x mixed oxide (with molar ratio Ce/Mn = 1) were prepared by sol-gel method using citric acid as a chelating agent and calcined at 500 °C. The silver catalysts (1 wt.% Ag) over the obtained supports were synthesized by the incipient wetness impregnation method with [Ag(NH₃)₂]NO₃ aqueous solution. The selective catalytic reduction of NO by C₃H₆ was investigated in a fixed-bed quartz reactor using a reaction mixture composed of 1000 ppm NO, 3600 ppm C₃H₆, 10 vol.% O₂, 2.9 vol.% H₂ and He as a balance gas, at WHSV of 25,000 mL g⁻¹ h⁻¹.The physical-chemical properties of the as-prepared catalysts were studied by several characterization techniques, such as X-ray fluorescence analysis, nitrogen adsorption/desorption, X-ray analysis, Raman spectroscopy, transmission electron microscopy with analysis of the surface composition by X-ray energy dispersive spectroscopy and X-ray photo-electron spectroscopy. Silver oxidation state and its distribution on the catalysts surface as well as the support microstructure are the main factors determining the low temperature activity in NO selective catalytic reduction. The most active Ag/CeMnO_x catalyst (NO conversion at 300 °C is 44% and N₂ selectivity is ~90%) is characterized by the presence of the fluorite-type phase with high dispersion and distortion. The characteristic “patchwork” domain microstructure of the mixed oxide along with the presence of dispersed Ag⁺/Ag_n^δ+ species improve the low-temperature catalyst of NO reduction by C₃H₆ performance compared to Ag/CeO₂ and Ag/MnO_x systems.

Co/TiO₂ catalysts with different cobalt loadings (3.8, 7.5 and 15 wt%) were prepared by impregnation method of Co(NO₃)₂ 6H₂O over titania. Samples containing Co(NO₃)₂·6H₂O and TiO₂ in stoichiometric proportions in order to obtain CoTiO₃ and Co₂ TiO₄ phases were also synthesized. The effect of the calcination treatment at two different temperatures, 550 and 1150 °C, was investigated. Characterizations by several techniques, such as XRD, UV–vis–NIR, DRS, Raman and XPS, were carried out. XRD showed the coexistence of three phases: CoTiO₃; Co₂TiO₄ and Co₃O₄ after calcination at 550 °C, while calcination at high temperature (1150 °C) led to single-phase systems (CoTiO₃ or Co₂TiO₄). Diffuse reflection and XPS spectroscopy showed that divalent cobalt occupies octahedral sites in the ilmenite phase, and both tetrahedral and octahedral sites in the spinel phase. The catalytic performances of the prepared catalysts were evaluated in the oxidative dehydrogenation reaction (ODH) of ethane to ethylene, as a function of the Co content for Co/TiO₂ catalysts and as a function of the calcination temperatures for the CoTiO₃ and Co₂TiO₄ phases. Co(7.5)/TiO₂ was the most active, although the conversion of ethane decreased in the first 150 min of the reaction, reaching values comparable to those of Co₂TiO₄ and CoTiO₃; however, Co(7.5)/TiO₂ was confirmed as having the best selectivity to ethylene in comparison with the bulk phases, CoTiO₃ and Co₂TiO₄. The influence of the reaction mixture composition, specifically the presence of water, at different percentages, was investigated. There is a decrease in the overall ethane conversion and an increase in the ethylene selectivity when the percentage of water increases. This behavior can likely be attributed to an increase in the surface concentration of hydroxyl species (OH), resulting in heightened surface acidity.

The reaction of octakis(3-chloropropyl)octasilsesquioxane with four equivalents of 1-hexylimidazole or 1-decylimidazole gave two products labelled as HQ-POSS (hexyl-imidazolium quaternized POSS) and DQ-POSS (decyl-imidazolium quaternized POSS) as regioisomer mixtures. An investigation of the biological activity of these two compounds revealed the higher antimicrobial performances of HQ-POSS against Gram-positive and Gram-negative microorganisms, proving its broad-spectrum activity. Due to its very viscous nature, HQ-POSS was adsorbed in variable amounts on the surface of biologically active oxides to gain advantages regarding the expendability of such formulations from an applicative perspective. Titania and 5 wt% Cu on titania were used as supports. The materials 10HQ-POSS/Ti and 15HQ-POSS/5CuTi strongly inhibited the ability of Pseudomonas PS27 cells—a bacterial strain described for its ability to handle very toxic organic solvents and perfluorinated compounds—to grow as planktonic cells. Moreover, the best formulations (i.e., 10HQ-POSS/Ti and 15HQ-POSS/5CuTi) could prevent Pseudomonas PS27 biofilm formation at a certain concentration (250 μg mL⁻¹) which greatly impaired bacterial planktonic growth. Specifically, 15HQ-POSS/5CuTi completely impaired cell adhesion, thus successfully prejudicing biofilm formation and proving its suitability as a potential antifouling agent. Considering that most studies deal with quaternary ammonium salts (QASs) with long alkyl chains (>10 carbon atoms), the results reported here on hexylimidazolium-based POSS further deepen the knowledge of QAS formulations which can be used as antifouling compounds.

In recent years, increased attention to air pollutants such as NO_x has led the scientific community to focus meaningfully on developing strategies for NO_x reduction. Selective catalytic reduction of NO_x by ammonia (NO SCR by NH₃) is currently the main method to remove NO_x from diesel engine exhaust emissions. The catalysts with typical V₂O₅-WO₃/TiO₂ (VWTi) composition are widely used in NH₃-SCR for their high NO_x conversion activity, low cost, and robustness, especially concerning sulfur poisoning. However, in real diesel engine working conditions, the thermal and hydrothermal aging of catalysts can occur after several hours of operation at high temperature, affecting the catalytic performance. In this study, the stability of a commercial VWTi monolith, self-supported and containing glass fibers and bentonite in its matrix, was investigated as a case study. In laboratory conditions, NO SCR tests were performed for 50 h in the range of 150 to 350 °C. Subsequently, the VWTi monolith was thermally and hydrothermally aged at 600 °C for 6 h. The thermal aging increased the NO_x conversion, especially at low temperature (<250 °C), while the hydrothermal aging did not affect the SCR. The differences in NO_x conversion before and after aging were associated with the change in vanadium and tungsten oxide surface coverage and with the reduction in the surface area of catalysts. In order to correlate the change in SCR activity with the modifications occurring after aging processes, the monolithic samples were characterized by several techniques, namely XRD, SSA and pore analysis, TPR, XPS, Raman, TGA and SEM/EDX.