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This manuscript is focused on the relationship between sol-gel synthesis processes and the development of new active phases with fitted morphology, porosity and surface chemistry. The influence of the above parameters on the catalytic performance of the prepared materials for the aromatization of n-hexane to benzene is also evaluated. Different series of catalysts were prepared, either using noble metals (i.e., Pt) or metal oxides (i.e., Mo, W), as active phases. In both cases, the catalytic performance and stability of classical aromatization catalysts was significantly improved. Interesting one-pot carboreduction process of the metal oxide during carbonization is suggested as a real alternative for the preparation of high-performance aromatization catalysts, leading to the formation of less acidic and non-stoichiometric oxides and carbides. ; ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI 2018-099224-B100 ; Nano4Fresh project as part of PRIMA Programme - European Union PCI2020-112045

This work was financially supported by the Spanish Projects, ref. RTI2018-099224-B-I00 from MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa", and ref. B-RNM486-UGR20 supported by Junta de Andalucia. ; Graphitic carbon nitride (g-C3N4) was used to enhance the photocatalytic activity of ZnO nanoparticles for the degradation of 5-fluorouracil (5-FU) cytostatic drug under UV-LED irradiation. CN/ZnO composites were synthetized by an easy one-pot thermal method, varying the g-C3N4 loading, i.e., from 10 to 67 wt% and a post-thermal exfoliation in air. The physicochemical and optical properties of the materials were analyzed by several techniques. CN/ZnO composites showed a corallike structure of spherical ZnO wurtzite particles on the g-C3N4 structure. In general, the synergism and heterojunction interface between both phases allowed the enhancement of the mesoporosity, light absorption ability, and the aromaticity of the corresponding composites. Moreover, the photocatalytic activity of the CN/ZnO composites was increased with the addition of g-C3N4 in comparison with pristine ZnO. The highest activity was found for the composite containing 25 wt% of g-C3N4 (i.e., CN25/ZnO), reaching the total degradation of 5-FU and a mineralization of 48% at 180 min, as well as a good photostability during four reuse cycles. Experiments with different pH solutions and scavengers allowed for the assessment of the reactive oxygen species (ROS) involved in the 5-FU degradation pathway, with radicals and non-radical species as the main responsible active species. Furthermore, a tentative photocatalytic mechanism was proposed for CN/ZnO composites. ; Spanish Government RTI2018-099224-B-I00 MCIN/AEI/10.13039/501100011033/FEDER ; Junta de Andalucia B-RNM486-UGR20

Graphene oxide (GO) is used to enhance the photocatalytic activity of ZnO nanoparticles for the degradation of vanillic acid (VA) under simulated solar light and visible-LED (λ > 430 nm). ZnO-GO composites are prepared by a mixing and sonication process with different GO loadings (i.e., from 1.8 to 6.5 wt.%). The materials are extensively characterized by thermogravimetric analysis (TGA), physisorption of N2 , X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), point of zero charge (pHPZC), and UV-Vis diffuse reflectance spectroscopy (DRUV). The presence of GO increases the photocatalytic activity of all the prepared composites in comparison with the pristine ZnO. The highest photocatalytic activity is found for the composite containing 5.5 wt.% of GO (i.e., ZnO-GO5.5), reaching a VA degradation of 99% and 35% under solar light and visible-LED, respectively. Higher TOC removal/VA degradation ratios are obtained from the experiments carried out under visible-LED, indicating a more effective process for the mineralization of VA than those observed under simulated solar light. The influence of hole, radical, and non-radical scavengers is studied in order to assess the occurrence of the reactive oxygen species (ROS) involved in the photocatalytic mechanism. The study of the photo-stability during three reuse experiments indicates that the presence of GO in the composites reduces the photocorrosion in comparison with pristine ZnO. ; Spanish Project ref. RTI 2018-099224-B100 funded by ERDF/Ministry of Science, Innovation and Universities ; State Research Agency and the Nano4Fresh project (ref. PCI2020-112045), as part of the PRIMA Programme supported by the European Union

A series of carbon aerogels doped with iron, cobalt and nickel have been prepared. Metal nanoparticles very well dispersed into the carbon matrix catalyze the formation of graphitic clusters around them. Samples with different Ni content are obtained to test the influence of the metal loading. All aerogels have been characterized to analyze their textural properties, surface chemistry and crystal structures. These metal-doped aerogels have a very well-developed porosity, making their mesoporosity remarkable. Ni-doped aerogels are the ones with the largest surface area and the smallest graphitization. They also present larger mesopore volumes than Co- and Fe-doped aerogels. These materials are tested as electro-catalysts for the oxygen reduction reaction. Results show a clear and strong influence of the carbonaceous structure on the whole electro-catalytic behavior of the aerogels. Regarding the type of metal doping, aerogel doped with Co is the most active one, followed by Ni- and Fe-doped aerogels, respectively. As the Ni content is larger, the kinetic current densities increase. Comparatively, among the different doping metals, the results obtained with Ni are especially remarkable. ; This research is supported by the FEDER and Spanish projects CTQ2013-44789-R (MINECO) and P12-RNM-2892 (Junta de Andalucía). A.A. is grateful to the European Union for his Erasmus Mundus fellowship, Program ELEMENT. J. C.-Q. is grateful to the Junta de Andalucía for her research contract (P12-RNM-2892). We thank the "Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente" (UGR) for its technical assistance"