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Composites of Ag and TiO2 nanoparticles were synthesized in situ on cotton fabrics using sonochemical and solvothermal methods achieving the successive formation of Ag-NPs and Ti-NPs directly on the fabric. The impregnated fabrics were characterized using ATR-FTIR spectroscopy; high-resolution microscopy (HREM); scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS); Raman, photoluminescence, UV-Vis, and DRS spectroscopies; and by tensile tension tests. Results showed the successful formation and impregnation of NPs on the cotton fabric, with negligible leaching of NPs after several washing cycles. The photocatalytic activity of supported NPs was assessed by the degradation of methyl blue dye (MB) under solar and UV irradiation revealing improved photocatalytic activity of the Ag–TiO2/cotton composites due to a synergy of both Ag and TiO2 nanoparticles. This behavior is attributed to a diminished electron–hole recombination effect in the Ag–TiO2/cotton samples. The biocide activity of these composites on the growth inhibition of Staphylococcus aureus (Gram+) and Escherichia coli (Gram−) was confirmed, revealing interesting possibilities for the utilization of the functionalized cotton fabric as protective cloth for medical applications.

This work presents the hydrothermal synthesis of Dandelion flower-like bimetallic oxide for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The synthesized oxide and respective activated catalysts were characterized by Fourier transform infrared- attenuated total reflectance (FTIR-ATR) spectroscopy, nitrogen physisorption, X-ray diffraction (XRD), Scanned electron microscopy-energy dispersive spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). The oxide sample exhibited a flower-like core-shell structure (TEM) and suitable BET surface area for the intended application, (133.4 m2.g−1). The FTIR-ATR analysis confirmed the decomposition of the organic precursor in the synthesized catalyst. Two activation methods were followed for the oxide sample sulfidation, namely, in-situ high-pressure sulfidation and ex-situ low-pressure sulfidation. Also, the TEM micrographs of sulfided catalysts showed that the core-shell structure prevailed. The HDS of DBT activity results showed that catalyst sulfided under high-pressure resulted in enhanced activity, 2.4 times than the low-pressure sulfided catalyst, owing to the high degree of sulfidation (XPS) and the presence of short/curved MoS2 slabs (XRD & TEM). The activity of the df-NiMo catalyst was compared with the trimetallic NiYMo catalyst.

Multimetallic systems, instead of monometallic systems, have been used to develop materials with diverse supported species to improve their catalytic, antimicrobial activity, etc., properties. The changes in the types of nanospecies obtained through the thermal reduction of ternary Ag

A partir de que se declaró la pandemia causada por el virus SARS-CoV-2, se han realizado una importante cantidad de trabajos para incrementar la protección de las personas ante este problema. El uso de mascarillas y equipo de protección personal es recomendado por la OMS para evitar la propagación del virus. En la actualidad, hay un campo de investigación de creciente interés en el desarrollo de mascarillas y otros materiales de protección que no solo pueden capturar las gotas de bioaerosol, sino que también inactiven al virus. Este es un paso importante para prevenir la propagación del COVID-19 y otras enfermedades infecciosas. El desarrollo de nuevos nanomateriales con propiedades biocidas que puedan ser incorporados en las mascarillas puede ayudar a alcanzar este objetivo incrementando la protección de los seres humanos contra el COVID-19. Efectivamente, estos nuevos dispositivos funcionarían contra cualquier otro virus o bacteria que llegara a presentarse en el futuro.

Here we reported an experimental analysis of Al2O3-TiO2 binary mixed oxides used as supports of NiW hydrodesulfurization catalysts. The series of supports were prepared by soft template sol-gel synthesis assisted by four different surfactants (P-123(P), F-68(F), L-64(L) and CTAB(C)). The characterization results showed substantial differences in the formation of the mixed oxide, the surface, and the electronic. Noteworthy was the sharp unimodal pore-size distribution obtained in all cases. The surface composition measured by XPS confirmed surface enrichment with alumina, changing the activity of the NiW catalysts. The morphology of the active NiWS phase presented average slab length and stacking of about 2.3 nm and 2 slabs. Meanwhile, large quantities of curved slabs were observed. This fact confirmed that the WSx cluster interacts preferentially with the Al atoms instead with the Ti atoms. The highest activity was observed in the NiW/AlTi-P and NiW/AlTi-F sulfided catalysts. We noticed that the activity is related not only with the sulfidation degree, the Ni promotion, or the slabs length and staking but also with the slab shape and the interaction with the support. The results of this work confirm that these AlTi-x samples are suitable to be used as supports of hydrodesulfurization catalysts.

In terms of a method based on Cauchy integrals, we have obtained a robust analytic expression to predict a unique physical solution for the Scholte slowness in all range of possible elastic and isotropic media. Proper analysis of the discontinuities of the secular Scholte equation allows the identification of the velocity of the evanescent wave in one of three possible regimes. When the liquid phase tends to vanish, it was observed: a) the Rayleigh wave solution or the free surface limit, and b) the rarefied fluid medium limit, where there exists a gradual extinction of the Scholte wave as both the density and velocity of the fluid decrease. In general terms, the results show that the propagation speed of a Scholte wave is less than or equal to that of a Rayleigh wave.

A series of mixed Al2O3-Ga2O3 oxides were prepared with different Ga2O3 content (labeled as AlGa-x; where x is the wt % of Ga2O3) by precipitation method. The oxides were then used as supports of palladium (2 wt %) catalysts (labeled as Pd/AlGa-x). Both series of samples, AlGa-x and Pd/AlGa-x were characterized by several techniques such as Raman spectroscopy, XPS, XRD, SEM, and HRTEM, and were tested in the 2-propanol dehydration reaction. The steady-state conversions displayed by the Pd/AlGa-x series was almost twice as that obtained for the AlGa-x series in all the range of tested temperatures. It was worth noting that the presence of palladium changed the yield observed for the AlGa-x series mainly at low temperatures. While at high temperatures the Lewis acidity provided by the well dispersed Pd nanoparticles increased the activity considerably and improved the propylene production. A balance between the dispersion of palladium and the surface acidity, both related to the Ga2O3 content was responsible for the observed catalytic behavior.

This article reviews the current state and development of thermal catalytic processes using transition metals (TM) supported on zeolites (TM/Z), as well as the contribution of theoretical studies to understand the details of the catalytic processes. Structural features inherent to zeolites, and their corresponding properties such as ion exchange capacity, stable and very regular microporosity, the ability to create additional mesoporosity, as well as the potential chemical modification of their properties by isomorphic substitution of tetrahedral atoms in the crystal framework, make them unique catalyst carriers. New methods that modify zeolites, including sequential ion exchange, multiple isomorphic substitution, and the creation of hierarchically porous structures both during synthesis and in subsequent stages of post-synthetic processing, continue to be discovered. TM/Z catalysts can be applied to new processes such as CO2 capture/conversion, methane activation/conversion, selective catalytic NOx reduction (SCR-deNOx), catalytic depolymerization, biomass conversion and H2 production/storage.

The isomorphous substitution of $$\hbox {Al}^{3+}$$ and/or $$\hbox {Fe}^{3+}$$ cations into the erionite zeolite framework were studied through periodic density functional theory computations. Taking as reference the Mulliken charges for siliceous framework computed in previous work (Antunez-Garcia et al. in J Mol Struct 1059:232–238, 2014), the present results show that the basicity of ERI zeolite increases when those cations are introduced into the framework. It was also observed that when at least two $$\hbox {Si}^{4+}$$ cations are isomorphically substituted by $$\hbox {Fe}^{3+}$$ in the unit cell of the erionite zeolite, it acquires magnetic properties. The results show that a specific net-spin polarization (up or down) could be correlated with particular configurations of erionite zeolite, containing ferric iron.

A series of Al-doped Na-TiO2 nanorods (AlTi-nR-x) varying the Al2O3/TiO2 (Al/Ti) ratio was synthesized by hydrothermal method. TEM results revealed well-defined nanorod like shape morphology. XPS results confirmed the presence of Al inside the samples and a slight increase in electron density around the Ti atom. Calcined materials were evaluated in the CO2 hydrogenation (HYD) in a continuous flow-microreactor at 280–340 °C under atmospheric pressure. Results from this work exposed that all AlTi-nR-x materials have great potential to be used as CO2 HYD catalysts. However, the best catalytic performance was obtained with the AlTi-nR-0.5 catalysts, which also displayed high selectivity (82%) towards methanol.

The influence of aluminum atoms on the surface and structural properties of distinct mixed oxides MgAl-x (x=Al/(Al+Mg)= 0, 0.20, 0.25, 0.33 and 1.0) was studied. Hammet titration results showed that the isomorphic substitution of Mg by Al atoms induces a basicity character decrease. Theoretical DFT studies of MgAl-x oxides basicity through the oxygen Milliken charges showed a similar trend to that observed experimentally. The effect in the textural properties as a function of the Al content was observed reflected directly in the surface area and pore size distributions. Noteworthy was to observed the morphological modification on the mixed oxides with the Al content, passing from nanorods in pure MgO to hexagonal platelets in the binary oxides.

Two zeolite structures (mordenite and ZSM-5) were crystallized as a mesostructure by a one-pot hydrothermal method using a supramolecular assembly and applying cetyltrimethylammonium bromide (CTAB) as a surfactant. The as-prepared materials were subjected to a pillaring process with amorphous SiO2 forming MFI-P and MOR-P pillared systems. The textural properties were significantly improved due to the efficient pillaring process, i.e., surface areas increased from 255 to 687 m2/g for MFI and from 393 to 710 m2/g for MOR. The zeolitic materials grew in the form of lamellar mesostructures when CTAB was used as a bulk filler between the laminar arrays of zeolites as revealed by transmission electron microscopy and X-ray diffraction. The lamella sizes were in the range of ~ 2.5 nm, which is similar to one unit cell of the growing zeolite for both samples. These results are consistent with the theoretical calculations obtained by the Powdercell program for the X-ray diffraction powder pattern of the mesostructured lattice for both samples. It was found that calcining of the as-synthesized samples at 550 °C leads to a non-congruent collapse of the mesostructure.

On the basis of the density functional theory (DFT) calculations, the successive isomorphic substitution of one to six tetrahedrally coordinated Si cations by trivalent Al was systematically studied. As a result of exploring a significant number of configurations, without using a priori assumptions, it was found that the Al atoms are accommodated according to the ground state sequence in the tetrahedral sites TI ​− ​TIII ​− ​TIII ​− ​TI ​− ​TIII ​− ​TIII. The results in the general show: a) Al cations preferentially occupy TIII positions, b) the distribution of cations in the framework does not violate Lowenstein’s rule, c) the distribution of cations in the framework does not satisfy Dempsey’s rule, and d) only one Al cation is found per ζ-cage.

A low-temperature and template-free synthesis method was developed to prepare MoS2 nanotubes by sulfidation of bulk NiMo oxide. The ex-situ gas-phase low-pressure sulfidation of NiMo oxide resulted in multi-walled MoS2 nanotubes and NixSy spheres. Meanwhile, the in-situ liquid phase high-pressure sulfidation led to nanotubes formation by self-assembly of MoS2 nano-bricks vertically oriented towards the outer surface as observed by HRTEM analysis. The sulfided catalysts were evaluated for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) in a batch reactor. Catalyst sulfided under ex-situ conditions exhibited good performance (76 % DBT conversion with an initial reaction rate 24 × 10−8 molDBT.(gCat.s)-1). The in-situ sulfided catalyst showed an outstanding activity (99 % DBT conversion with an initial reaction rate 105 × 10−8 molDBT.(gCat.s)-1). Which means that the in-situ sulfidation method dramatically increased the initial reaction rate by four times. A mathematical expression (RKC equation) was derived to correlate the size of the regular hexagonal MoS2 nanoparticles with its activity, for which the experimental results were validated.

The electronic properties of LTA-type zeolites in their siliceous, aluminized, and ferric frameworks compositions, all of which were selected in their sodium ion-exchange form and under anhydrous conditions, were studied through DFT computations. In the case of an aluminized framework, it was found that the non-Lowensteinian configuration is not only energetically more favorable but also has better electronic conductivity than the Lowensteinian framework. The two different ferric frameworks under consideration presented distinct magnetic nature and higher acidity compared to aluminized ones. Furthermore, it was observed that the purely siliceous LTA framework presented an inversion in the Lowdin charge trace behavior, suggesting that it is associated with its hydrophobic nature.

This investigation deals with a consensus electronic property analyses, for NbSe2 over graphene using Density Functional Theory. Depending on how you construct your initial system under investigation, either starting with Armchair, Chiral or Zig-zag for a graphene layer, final different results for the electronic properties should be anticipated. It is critical to take in consideration the brim edges effect in the initial conditions because different final results will be obtained. Energy bands and charge density profiles will be presented for each case under study. For pristine graphene Eg (forbidden energy gap between the Valence and Conduction bands) of 0.24 eV (Armchair), 0.19 eV (Chiral) and 0.13 eV (Zig-zag) were obtained respectively. In addition, defect on the structure (vacany defect) was considered, in order to simulate a real scenario which could be compared to an experimental result while constructing graphene-defect-NbSe2 system. To our knowledge, this is the first time that such a kind of investigation is presented.

This article presents the results of a comprehensive study of copper-exchanged mordenite samples prepared from its ammonia and protonated forms (Si/Al = 10) using two different ion exchange methods: conventional and microwave (MW)-assisted. The protonated H-MOR-10 sample was obtained by calcination of commercial NH4MOR-10, in this case, a slight degradation of the mordenite framework was observed, but the resulting defects were partially restored after the first ion-exchange procedure of protons for copper ions. The level of copper exchange in the studied materials was found to be limited to 70%. Regardless of the exchange procedure, the replacement of ammonium or proton ions with copper led to a linear increase in the a/b ratio of cell parameters in accordance with an increase in the level of copper exchange, which means that all Cu2+ cations are ion-exchangeable and enter the main mordenite channel. Thermal analysis indicated a correlation between the replacement of various ammonium and hydroxyl groups by copper ions during the exchange treatment and their dehydroxylation energy during thermal decomposition. As a conclusion: MW-assisted treatment proved itself as an efficacious method for the synthesis of copper-exchanged mordenites, which not only significantly reduces preparation time but leads to a systematically higher copper exchange level.

In this work, the effect of layered TiO2 anatase nanorod preparation and application were systematically analyzed. The nanoparticles were widely characterized and applied in the photocatalytic degradation of red amaranth toxic dye. The nanorod morphology changed with the type of acid treatment; they decreased in length and diameter with the increase in acid concentration. The use of HCl induced a preferential growth of (101) planes, while HNO3 favored the formation of the (004) face. Likewise, the HCl acid treatment allowed the incorporation of small quantities of Cl − ions on the surface of TiO2 anatase, impacting the activity positively. Otherwise, the presence of surface nitrogen was not detected when treated with nitric acid. The characterization and activity result allowed us to propose structure–activity correlations with morphology and Cl − ions. It was revealed that the Na removal enhanced reactivity revealing to the enhanced crystallinity of TiO2 nanorods is responsible for the photocatalytic activity results. We conclude that these nanomaterials are suitable as catalysts for the degradation of dye pollutants in water if a fine-tuning is done with acid solutions.

A novel, efficient, and eco-friendly template-free hydrothermal method developed for the synthesis of Dandelion shape trimetallic (Ni, Y, Mo) oxide hollow microspheres decorated with nanosheets is reported. The oxide state material was transformed into a sulfide catalyst without losing of the core-shell structure and was used for the hydrodesulfurization (HDS) of the dibenzothiophene. The nanostructured sulfided catalyst exhibited excellent HDS behavior with an initial reaction rate of 42 × 10−8 molDBT.(gcat.s)-1 (at 320 °C and 55 bar hydrogen pressure) as well as outstanding particle morphology stability after the catalytic test, as shown by SEM and HRTEM analysis of the used catalyst. The Dandelion type microspheres containing Ni, Y, and Mo metal oxides with core-shell architecture which after sulfidation could be used as efficient and selective catalysts for the diesel cut industrial hydrodesulfurization. A plausible reaction mechanism also proposed for the formation of Dandelion flower-like hollow sphere oxide catalyst.

The present work is a theoretical study of the different frameworks and composites of faujasite (FAU) zeolite. Most of the computations for composites were performed by embedding M2 metal clusters (M = Ni, Cu, Fe and Au) within the Al2Si40O96 FAU zeolite framework. Results showed that, in this framework, the difference between the α and β spin induced an unfolding band structure for Cu2 and Au2 clusters. Thus, their respective band gap energy decreased. In addition, low energy band gap values are associated with composites in which the cluster presents practically no hybridized orbitals. In particular, the charge trace of a zeolitic framework was identified as a fingerprint that is different for other types of zeolites and composites. In this charge trace, the framework atoms on equivalent sites with lower charge values were identified as being responsible for clusters adsorption.

A high surface area binary Al2O3-Ga2O3 oxide (AlGa) (75% wt%/25 wt%) was prepared by a single-stage precipitation method, and then used as support for noble metal catalysts (3 wt% nominal metal content). Effect of noble metals (Os, Pd, Rh, and Pt) on the surface distribution and the type of species formed were investigated by SBET, XRD, SEM-EDS mapping, HRTEM, DRIFT-CO and XPS techniques and tested in the Water-Gas Shift (WGS) reaction carried out in a fixed bed reactor at atmospheric pressure and temperature range 160–400 °C. The activity tests revealed that the reactivity of the catalyst followed the order: Pd/AlGa > Pt/AlGa > Rh/AlGa > Os/AlGa. The Pd and Pt-based catalysts presented the light-off reaction temperature at about 280 °C while the Os and Rh-based ones were activated at 300 °C and 325 °C, respectively. For the best Pd/AlGa catalyst, the DRIFTS spectra of chemisorbed CO revealed the presence of isolated peripheral or basal palladium species suggesting the importance of those species for the WGS reaction. For the Pt/AlGa catalyst, the combined EDS mapping and HRTEM studies indicated the highest dispersion of the metal phase among the catalysts studied. In this case, the absence of a correlation between the catalyst activity and metal dispersion suggests that factors other than metal dispersion control its catalytic performance.

The adsorption of MoS2 monolayer over reduced graphene oxide (RGO) using first-principles calculations based on the density functional theory was investigated. Also, the hybrid system was synthesized by the solvothermal method. The theoretical calculations of the band structure showed an electronic charge transfer from the MoS2 toward graphene. On the other hand the hybrid sample presented high dispersion of MoS2 on RGO.

SSCI-VIDE+ECI2D+JRD:GBE; International audience; This study reports the electrocatalytic activity of alloyed Pt10-x-Fe-x/CNTs (x = 1, 2, 3, 4, 5) and Pt/CNTs nanoparticles. These materials were synthesized using the Brust-Schiffrin method and were tested as potential anodic electrocatalysts in a direct methanol fuel cell (DMFC). SEM, EDS, XRD, TEM and TGA studies were performed to confirm the formation of Pt-Fe alloyed nanoparticles. The nanoalloys material supported on CNTs showed a volcano-type behavior for methanol electro-oxidation when varying the relative Fe:Pt stoichiometry. An enhancement of electrocatalytic activity was observed for alloyed nanoparticles with Fe:Pt = 4:6) led to depleted activities caused by a decrease of the methanol dehydrogenation process on the alloyed nanoparticles surface. Cyclic voltammetry and chronoamperometry measurements indicated that a ratio of Fe:Pt = 3:7 is the optimum to obtain the best electrocatalytic activity on CNTs-supported alloyed nanoparticles for methanol oxidation reaction. (C) 2016 Elsevier Ltd. All rights reserved.

Two series of molybdenum carbides are prepared from MoO3 by temperature programmed reduction (TPR), differing in feed gas composition (20 and 40% CH4/H2). The heating ramp consists of two steps, one from ambient temperature to 973 K, at a rate of 10 K/min; the second from 973 K up to the final temperature (1023, 1073, 1123, 1173 K), at a rate of 0.5 K/min. The Mo2C (hcp) phase is identified for the series prepared with 20% CH4/H2 at different temperatures, with surface areas between 20 and 27 m2/g. Also found is a mix of the MoC and Mo2C (hcp) phases for the series prepared with 40% CH4/H2 at temperatures above 1023 K, with surface areas between 9 and 19 m2/g. Both series of catalysts reach 100% conversion of cyclohexene in 5 h or less, with those catalysts prepared with a 40% CH4/H2 gas mix reaching maximum conversion in the least time. Catalysts are compared to a commercial molybdenum carbide reagent as a reference.

The contribution of (Ce1-X Zr X )O2 additives to alumina supports prepared by sol-gel and the catalytic properties of PdO/Al2O3–(Ce1-X Zr X )O2 catalysts (~0.3 wt% Pd, ~5 wt% (Ce1-X Zr X )O2) in CO oxidation was herein investigated. The addition of (Ce1-X Zr X )O2 to the support enhanced the surface area and decreased the size of Al2O3 particles. The UV–Vis bands of PdO particles and Pd2+ ions indicate that zirconia in (Ce1-X Zr X )O2 promotes palladium-support interactions by forming highly dispersed PdO particles. Temperature-programmed reduction (TPR) in hydrogen revealed that ceria enhanced the redox capacity of the supports while zirconia lowered the reduction temperature of palladium oxide species. The comprehensive study revealed that the Ce/Zr ratio was a key factor influencing the catalytic activity of samples in CO oxidation, because palladium oxide-support interactions had a significant effect in changing of the reducibility of samples. So, the PdO/Al2O3–(Ce0.5Zr0.5)O2 exhibited the highest catalytic activity.

Here we report on the results of our theoretical study of 1H-MoS2 clusters grown on graphene oxide. First, we studied graphene cluster, graphene oxide (1,2) and (1,3) ether-like monolayers with a Stone-Wales defect. Secondly, a 1H-MoS2 nanoparticle was grown over the defect creating a sandwich like structure. For all considered structures energy bands as well as total and partial density of states (DOS) were calculated in order to inquire about their electronic behaviour. It has been found that for graphene oxide (1,2) ether-like with 1H-MoS2cluster located over the defect and either terminating as Mo- or S-edges, it behaves like a semi metal, while for graphene oxide (1,3) ether-like it yields semiconductor behaviour, respectively. Our main concern was the sandwich, in which total and partial DOS indicate a strong hybridisation of bands formed by C p-, S p-, Mo d- especially for graphene oxide (1,3) Mo- or S-edges.

Molybdenum disulfide (MoS2) is a compound very useful for its properties; it is used as a lubricant, catalyst in hydrodesulfurization, in hydrogen fuel storage, etc. In this work MoS2 hexagonal nanoplates were synthesized at different temperatures and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). These nanoplates have a size of 25–35 nm as revealed by SEM. With aberration corrected STEM it was possible to measure the interatomic distance of Mo–Mo, which was found to be 2.8 A. The catalytic properties of the nanoplates were measured in the hydrodesulfurization of dibenzothiophene, showing high activity and high direct desulfurization pathway (DDS) selectivity for an unpromoted MoS2 catalyst. Theoretical calculations were performed in 2H-MoS2 as well as 2H-MoS2 with a rotation of 16° and 19° which was applied to the two S planes in the crystalline structure. The results obtained on the rotated 2H-MoS2 yielded indication of a small gap semiconductor of Eg = 0.38 eV when compared to the unrotated 2H-MoS2, which is a semiconductor of Eg = 2.00 eV. This tendency of the rotated crystalline 2H-MoS2 toward metallicity could be responsible for the enhancement of the catalytic properties observed in the material in question, compared to other MoS2-based catalysts.

El MoS2/OGR es un material híbrido que presenta un extraordinario comportamiento en las baterías de iones de litio (LIB) y en la reacción de evolución del hidrógeno (HER). Este material es capaz de sustituir al platino en la nueva generación de electrocatalizadores nanoestructurados. Este electrocatalizador usa las extraordinarias propiedades electrónicas del óxido de grafeno reducido (OGR) y los sitios activos en los bordes del MoS2. El comportamiento de este electrocatalizador híbrido sugiere una sinergía entre ambos sistemas. En este trabajo pesentamos la adsorción de OGR sobre una monocapa de MoS2 usando la Teoría del Funcional Densidad (DFT) y la síntesis de monocapas de MoS2/OGR mediante el método solvotermal. La energía de enlace y la distancia de adsorción entre las capas es de 3.7 meV y 3.33 A, respectivamente, muestran una débil interacción entre los sistemas. Se encontraron estables los conos de Dirac desplazados 0.3 eV hacia abajo del nivel de Fermi indicando la transferencia de electrones del MoS2 hacia el OGR. Esta transferencia de electrones puede ser la responsable la sinergía entre los sistemas. Las imagenes de alta resolución del microscopio electrónico de transmisión (HR-TEM) y el patron de difracción muestran la obtención de MoS2 en forma de monocapas, la alta dispersión del MoS2 en forma laminar sobre el OGR y remanentes de oxígeno en la muestra. The MoS2/RGO is a hybrid material exhibiting an extraordinary performance in lithiumion battery (LIB) and the hydrogen evolution reaction (HER). This material is able to replace platinum in the new generation of nanostructured electrocatalysts. This extraordinary electrocatalyst used electronic properties of reduced graphene oxide (RGO) and the active sites on the edges of MoS2. The behavior of this hybrid electrocatalyst suggests a synergy between the two systems. In this work we present the adsorption RGO on a monolayer MoS2 using the Density Functional Theory (DFT) and synthesis of monolayer MoS2/RGO by solvothermal method. It was found the binding energy of adsorption and the distance between the layers is 3.7 meV and 3.33 A, respectively, showing a weak interaction between the systems. We found stable Dirac cones displaced downward 0.3 eV of the Fermi level indicating the transfer of electrons from MoS2 to the RGO. This transfer of electrons may be responsible for the synergy between the systems. The images from (HR-TEM) and the di raction pattern show the MoS2 as monolayers added to the high dispersion of the MoS2 sheets formed on RGO as well as oxygen residue in the samples.

En el presente trabajo se estudió el efecto de la presencia de compuestos organometálicos de silicio en la reacción de hidrodesulfuración (HDS) de dibenzotiofeno (DBT) sobre cuatro catalizadores de NiMo soportados en γ-Al2O3 con diferente distribución de tamaño de poro (DTP). Se sintetizaron cuatro catalizadores, dos con distribución de tamaño poro bimodal y dos con distribución unimodal. Los soportes de los catalizadores se obtuvieron por los métodos solgel e hidrotermal, con el fin de lograr los dos tipos de DTP bimodal y unimodal. Las propiedades texturales, la composición química y la estabilidad térmica fueron determinadas para los soportes, los catalizadores frescos y los catalizadores gastados. Además se determinó la cristalinidad y naturaleza de la fase de cada uno de los soportes. La actividad catalítica de cada uno de los catalizadores sulfurados fue evaluada en un reactor por lotes para la reacción de HDS de DBT en presencia y ausencia de hexametilciclotrisiloxano, con el fin de determinar el impacto de la presencia del compuesto organometálico sobre la actividad catalítica. La composición de la mezcla de reacción fue medida a diferentes tiempos mediante cromatografía de gases. Se determinó la constante de reacción así como el orden global de la reacción. Se observó una clara disminución en la constante de velocidad de reacción para los cuatro catalizadores. Uno de los catalizadores con DTP bimodal presentó una mayor resistencia a la desactivación por efecto del organometálico de silicio. Este catalizador presentó una alta cantidad de poros con diámetro de poro promedio (DPP) de 10 nm, mientras que la cantidad de poros con DPP de 5 nm fue menor. Al comparar los cambios ocurridos en la DTP para cada uno de los catalizadores se concluyó que los compuestos organometálicos de silicio se adsorben de forma preferencial en los poros con DPP de 10 nm. En el caso del otro catalizador bimodal, se observó un alto efecto de desactivación, con base en la DTP se concluyó que la cantidad de poros ADP alrededor de los 10 nm no fue suficiente para retener el organometálico de silicio lo cual permitió el bloqueo de los poros más pequeños. The effect of an organometallic compound over the catalytic activity of four NiMo catalysts supported on γ-Al2O3 with different pore size distribution in the reaction of hydrodesulphurization (HDS) of dibenzothiophene (DBT) was studied. The catalysts were synthesized, two with bimodal pore size distribution (PSD) and two with unimodal PSD. In order to obtain distinct pore size distribution (bimodal and unimodal), the γ-Al2O3 supports were prepared by two different methods, sol-gel and hydrothermal. The surface properties, chemical composition and thermal stability were determined for all supports, as well as for fresh and spent catalysts. Besides the XRD analysis was performed for each support. The supports were impregnated via liquid impregnation. The catalysts evaluation in the HDS of DBT was made in a batch reactor under controlled conditions. Each one of the catalysts were evaluated with and without an organometallic silica compound (hexamethyl cyclotrisiloxane), searching to estimate the effect of the organometallic compound over the catalytic activity. The reaction rate constant and the reaction global order were calculated based on the gas chromatography results. A comparison between the activity of the catalyst with and without hexamethyl cyclotrisiloxane was made. An evident dimininution of the constant rate of the four catalysts was observed. One of the catalyst with bimodal PSD showed the highest resistance to deactivation by the organometallic. This catalyst present a higher quantity of pores with average pore diameter (APD) of aproximmately 10 nm and a lower quantity of pores with an APD of 5 nm. By comparing the changes on the PSD of each catalyst, it can be concluded that the silica compounds are preferably adsorbed inside pores with APD of 10 nm leaving the smaller pores free for the catalytic reaction. In the case of the other bimodal catalyst a high deactivation effect was observed, and it leads to conclude that there was not enough pores with high AVP, allowing the adsorption of the silica compound on the small pores.

Desde hace varias décadas el convertidor catalítico de tres vías (TWC por sus siglas en inglés) ha sido el sistema más efectivo para disminuir las emisiones de los principales contaminantes de los automóviles (CO, HC's y NOx), Actualmente, los componentes básicos de los convertidores catalíticos son paladio (Pd) soportado en alúmina (Al2O3) con varios aditivos (óxidos) como estabilizadores térmicos y promotores estructurales. El funcionamiento de estos catalizadores depende de varios factores como el método de preparación y su composición. En este trabajo se estudio el desempeño catalítico en la oxidación de monóxido de carbono (CO) de catalizadores a base de Pd soportado en una mezcla de óxidos de y-alúmina con ceria-circonia: Al2O3-(Ce1-xZrx)O2. Los soportes fueron preparados por el método de sol-gel, logrando materiales con áreas superficiales relativamente altas, en donde se encontró que, tanto la mezcla de óxidos de cerio y circonio ((Ce1-xZrx)O2), como el óxido de paladio (PdO), están dispersados en el soporte en forma de partículas muy pequeñas del orden de algunos nanómetros. La actividad catalítica se evaluó en términos de curvas de "ligth off' y se comparó la temperatura a la cual la reacción alcanzó el 50% de conversión de CO (T50%). Los catalizadores sometidos a un tratamiento previo de reducción resultaron más activos que los catalizadores oxidados, con T50% menores a 100 ºC. En ambos casos, los catalizadores que contienen la mezcla de ambos óxidos manifestaron mayor conversión de CO que los que contienen solo uno de ellos, o ninguno. Esto implica que el soporte juega un papel fundamental en el desempeño del catalizador, cuyas propiedades se vieron mejoradas por la presencia de ceria-circonia. El efecto de los aditivos revela una estrecha relación metal-soporte, en donde el óxido de cerio actúa como estabilizador de paladio en estado Pd2+ , el cual representa los sitios activos para la oxidación de CO. El óxido de circonia mejora las propiedades redox del soporte, es decir, promueve su reducción a menor temperatura. Since severa! decades the three-way catalytic converter (TWC) has been the most effective system to diminish the emissions of the main polluting agents of the automobiles (CO, HC's and NOx). At the moment, ¡the basic components of the catalytic converters