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A spectroscopic and microscopic investigation was made of the dynamics of bimetallic nanoparticles (NPs) in Co–Ni/MgAl2O4 catalysts used for the steam reforming of ethanol (SRE) reaction, consideri...

This study is dedicated to the development of a methodology based on supervised machine learning for soybean classification and justified as technological innovation to predict whether soybean classification is in the standard or non-standard established by normative instruction No. 11/2007 of the Ministry of Agriculture, Livestock, and Food Supply (MAPA). This study aimed to develop a website using supervised machine learning to classify soybeans, providing an assertive decision-making process in real-time. A technological tool was created to assist the farmer and the storage unit in the classification of soybeans, considering the perceived reality and potential instruments consistent with the reality of the area. Therefore, a website in Python language was created using the Pandas, Pandas Profiling, Seaborn, Matplotlib, NumPy, Scikit-learn, PyCaret, and Streamlit libraries. In the end, the system could predict whether the soybean is in the standard or non-standard established by the soybean classification normative. In this sense, the results showed the robustness and precision of the proposed new methodology.

We focus herein on understanding how the oxidation mechanism of glucose may be affected by the nature of the surface facets of Cu2O-based electrocatalytic sensors. To this end, we performed a series of in situ FTIR spectroelectrochemical experiments and DFT simulations by employing Cu2O cubes and octahedra as electrocatalytic sensors for glucose and other interferents. Interestingly, our in situ results demonstrated that the glucose oxidation mechanism displayed shape-dependent behavior, indicating that the glucose molecule can selectively adsorb on the Cu2O {1 0 0} facets relative to ascorbate and urate interferents in a process that probably occurs without the need for an external potential. However, when the same reaction was performed in the presence of Cu2O octahedra ({1 1 1} facets), the reaction was not selective, and the final product remained on the surface, blocking the sites for further glucose oxidation and leading to significantly lower electrocatalytic activities. Surprisingly, no bands related to the formation of Cu3+ species were detected, indicating that Cu3+ species do not participate in the reaction mechanism. This is very important because these species have been assumed to be the catalytically active sites for glucose oxidation. We believe that the results presented herein provide new insights into different aspects of the oxidation of carbohydrates and may inspire a deeper mechanistic investigation of other semiconductor materials and the development of optimized electrocatalysts.

The palladium(II)-mediated chemical uncaging reaction of propargylic substrates is a recent addition to the field of chemical biology and medicinal chemistry in the activation of bio and prodrug mo...

We reported herein the synthesis in high yields (>97%) of Ce0.9Sm0.1O2-δ nanowires displaying well-defined shape, size, and composition by a simple, fast, and low-cost two-step hydrothermal method. The Ce0.9Sm0.1O2-δ nanowires synthesis was followed by the wet impregnation of Ni without the utilization of any stabilizing agent. The Ni/Ce0.9Sm0.1O2-δ nanowires showed higher surface area, high concentration of oxygen vacancies at surface, and finely dispersed Ni particles with significantly higher metallic surface area as compared with catalysts prepared from commercial materials with similar compositions. Such unique and improved properties are reflected on the catalytic performance of the Ni/Ce0.9Sm0.1O2-δ nanowires towards ethanol steam reforming. The nanowires exhibited high yields for hydrogen production (∼60% of selectivity) and an exceptional stability with no loss of activity after 192 h of reaction at 550 °C. The reported results provide insights and can inspire high-yield production of nanostructured catalysts displaying controlled and superior properties that enable practical applications in heterogeneous catalysis.

Deposition on the surface of amberlite resin was conducted to produce two different types of bimetallic nanoparticles, combining one of three different metals (M = Cu, Ag and Ni) with Pd (M–Pd@R and Pd–M@R). To obtain the bimetallic nanoparticles, the four different metal ions were firstly immobilized on the resin surface by ion exchange and monometallic nanoparticles were formed by reduction of the metal ions with NaBH4. By changing the sequence of metal ion immobilization on the resin, six bimetallic supported catalysts were prepared. Surface oxidation of the metals on the surface layer is inhibited in some cases and the catalytic propensity for certain reactions is improved. After careful characterization by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption near edge structure, the activity of the catalysts was evaluated performing kinetic studies on the reduction reactions of 4-nitrophenol and phenylacetylene. The kinetic study revealed that the geometric factor, opening up catalyst sites through the ensemble effect, seems to be the main reason for the differentiated catalytic activity of the nanoparticle composites. Moreover, high selectivity for styrene in the hydrogenation of phenylacetylene was observed for Cu-containing catalysts, with almost total conversion of the substrate.

DDT (1,1,1-trichloro-2,2-bi(p-chlorophenyl)-ethane) and its metabolites (DDD, 1,1-dichloro-2,2-bis-(4′-chlorophenyl)ethane, and DDE, 1,1-dichloro-2,2-bis-(4′-chlorophenyl)ethylene) are persistent organic pollutants that can be catalytically degraded into a less toxic and less persistent compound. In this work, ecofriendly methodologies for catalyst synthesis, catalytic degradation of DDT and reaction monitoring have been proposed. Three types of Pd-based nanoparticles, NPs, (Pd, Au-on-Pd and Cu-on-Pd) were synthesized and used for catalytic hydrodechlorination of DDT and its metabolites. The structural and electronic properties of NPs were investigated using TEM and XAS spectroscopy. Au-on-Pd showed the highest hydrodechlorination efficiency within 1 h of reaction. To obtain the best reaction conditions, the effects of H2 flow and base addition Au-on-Pd NPs activity were investigated. To study the effectiveness of the different NPs, a solvent-free analytical method was optimized to detect and measure DDT and its by-products. The SPME-GC–MS method provided low detection limits (0.03 μg L−1) and high recovery (≥88.75%) and was a valuable tool for the NP degradation study. In this way, a green method for degradation and monitoring of DDT and its by-products in water was achieved.

The excess of capping agents used during the synthesis of nanoparticles is usually removed by solvent washing. The influence of the amount of polyvinylpyrrolidone (PVP) capping agent in the catalytic activity of palladium nanocubes was evaluated, after different numbers of washing cycles in the purification step performed after the syntheses of the nanoparticles. The effect of PVP amount on the hydrogenation of unsaturated carbon-carbon bonds was evaluated in terms of kinetic analysis and diffusion experiments. Five different catalysts were prepared utilizing the washing off procedure. All catalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, small angle X-ray scattering spectroscopy and dynamic light scattering. The reaction presented strong influence by the amount of PVP, which was determined to be due to a balance between the amount of capping agent and the structure of the substrate.

We report the optimization of both the support and the active phase of PdPt NPs supported on TiO2 nanowires to obtain highly active electro/photocatalysts for the oxygen reduction and water splitting reactions. This system displayed strong metal-support interactions, high concentration of oxygen vacancies, and PdPt NP were similar to 2 nm in size. By optimizing the loading of PdPt, both the photo- and electrocatalytic activities were improved compared to commercial materials. Interestingly, a volcano plot was obtained from the activity and the PdPt composition, and the Pd0.22P0.78-TiO2/C sample afforded the optimal performance. For instance, the amount of hydrogen produced from water splitting was 11.6 mmol/g(catalyst). For the ORR, the activity was similar to a commercial Pt catalyst, but a lower E-onset (0.87 V-RHE vs w 0.95 V-RHE) was detected. The variations in the activities with the composition correlated well with the variations in the electronic effects and the concentration of oxygen vacancies.

We reported the organic template-free synthesis of gold (Au) nanoparticles (NPs) supported on TiO2, SiO2, and Al2O3 displaying uniform Au sizes and high dispersions over the supports. The Au-based catalysts were prepared by a deposition–precipitation method using urea as the precipitating agent. In the next step, the solvent-free oxidation of benzyl alcohol was investigated as model reaction using only 0.08–0.05 mol% of Au loadings and oxygen (O2) as the oxidant. Very high catalytic performances (TOF up to 443,624 h−1) could be achieved. Specifically, we investigated their catalytic activities, selectivity, and stabilities as well as the role of metal–support interactions over the performances. The conversion of the substrate was found to be associated with the nature of the employed support as the Au NPs presented similar sizes in all materials. A sub-stoichiometric amount of base was sufficient for the catalyst activation and the observation of the catalysts profile over the time enable insights on their recyclability performances. We believe this reported method represents a facile approach for the synthesis of uniform Au-supported catalysts displaying high performances.

By a combination of theoretical and experimental design, we unraveled the effect of {111} and {100} surface facets on the electrocatalytic sensing activities and stabilities of metal oxides by employing Cu2O crystals as a model substrate and glucose as the analyte. We started by theoretically investigating the potential energy curves for the glucose interaction with the Cu2O {111} and {100} surface facets. We found that the glucose interaction energy was significantly higher for the {100} facets than for the {111} facets. Then, we experimentally observed that their electrocatalytic sensing performance displayed shape-dependent behavior. While the catalytic activities followed the order cubes > cuboctahedrons > octahedrons, their stabilities showed the opposite trend. The higher catalytic activity enabled by the {100} facets is explained by their stronger interaction with glucose. On the other hand, the higher stability allowed by the {111} facets is justified by their lower concentration of oxygen vacanci...

We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (∼2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.

The main purpose of this work is to contribute to the description of the acetone synthesis from ethanol employing Zn x Zr 1-x O 2-y based catalysts. The catalytic behavior of these solids was evaluated (isoconversion) in the acetone synthesis. The most active catalyst and m -ZrO 2 (used as a reference) were characterized by the following techniques: pyridine adsorption, TPD of NH 3 , TPD of CO 2 , TPD of ethanol followed by IR (DRIFTS)/MS, TPD of ethanol followed by XANES at the Zr K-edge and Zn K-edge and XRD in situ . The present study suggests that the main steps of the acetone generation from ethanol are the following: firstly, ethoxide species are generated and, then, they are dehydrogenated to acetaldehyde. Both steps are related to strong basic and acid sites. Acetaldehyde reacts with the O of the solid solution generating acetate species and vacancies on the catalyst surface. These carboxylate species condensate (strong basic sites) and generate acetone and CO 2 . Water dissociates on the vacancies of the catalyst and reoxidizes the its surface, closing the catalytic cycle. All these steps might occur on Zn +2 and on the species in its vicinity (XANES).

The effect of ceria in cobalt-ceria-alumina catalyst was studied using in situ X-ray near edge spectroscopy (XANES) at Co K-edge and Ce LIII-edge. The introduction of ceria in this catalyst resulted in a significant removal of Co from CoAl2O4 spinel phase to Co and CoO phases. The Co K-edge revealed the symmetry changes in Co according to the temperature and atmosphere in reduction process. We also showed the stability of Co sites as well the oxidation state of ceria in operando steam reforming of ethanol (SRE) reaction. After reduction of Ce4+ to Ce3+, no significant changes were observed by XANES. Gas Chromatography (GC) analysis showed a high ethanol conversion at 500 °C, high hydrogen yield and low formation of undesired products as methane and ethylene. The results showed a Co/Ce/Al2O3 catalyst as promising material to be applied in hydrogen production in SRE reaction.

The trans-2-phenylvinylboronic acid homocoupling reaction catalyzed by palladium nanocubes (Pd-NCs) was investigated by kinetics, spectroscopy, and poisoning experiments. The reaction was evidenced to be sensitive to the presence of the base, which acts synergistically with the substrate molecules and assists the leaching of Pd oxide (PdOx) species to the reaction medium. This species catalyzes the homocoupling reaction through the formation of Pd–Ox–B(OH)2R pretransmetalation intermediates, via coordination with the vinylboronic acid molecules, involving an oxo-palladium-type interaction. The reaction rate was not enhanced by the saturation of the reaction medium with O2, which is due to the oxidized nature of the Pd-NC surface.

A mechano-colloidal approach was developed to produce Au nano-tadpoles. It comprises the generation of seeds by ball-milling from a solid mixture containing a precursor, reductant, and capping agent, followed by the dispersion of this mixture in water leading to seeded-growth to generate the target nanoparticle morphology.

PtSnNi electrocatalysts (60: 40: 40 mass ratio) supported on Vulcan® XC-72 (Cabot) carbon and COOH-functionalized multiwalled carbon nanotubes (Cheaptubes®) with 15% of metal loading were prepared. The nanoparticles size of 2–3 nm for both supports was estimated by HRTEM. In the direct ethanol fuel cell experiments, PtSnNi/C presents 50 mA cm−2 reaching the maximum power density (MPD) of 12 mW cm−2 and decreasing at higher currents, while PtSnNi/MWCNT-COOH obtains similar values of MPD (60 mA cm−2), but keeping the best performance. By GC (gas chromatography) technique, it was possible to observe that the electrocatalyst supported on MWCNT-COOH favored the ethanol oxidation to acetaldehyde and acetic acid, although the material supported on Vulcan® XC-72 carbon presented almost 100% of selectivity for acetaldehyde. This behavior was maintained also when the current of 0.1 A was applied for 80 min. For the PtSnNi/C electrocatalyst, the selectivity to only acetaldehyde can be related to Sn and Ni dissolution process that can become the electrocatalytic activity similar to Pt/C, decreasing the power density as observed in our experiments. Established by EDS analysis, after 80 min of polarization, the Ni and Sn relative atomic ratio was lower on the catalytic anodic layer of PtSnNi/C than on PtSnNi/MWCNT-COOH.

Pt nanoparticles (Pt NPs) supported on carbon have been widely employed as electrocatalysts toward oxygen reduction reaction. The development of more efficient electrocatalysts that enable one to reduce or even not require the use of Pt is a central challenge. In addition to the control over the physical and chemical features of Pt NPs, metal support interactions can be employed to enhance activities via the generation and exposure of surface-active sites. In this context, we report herein the development of electrocatalysts composed of Pt NPs supported on TiO2 microspheres, that were subsequently impregnated onto carbon. We have found that, by optimizing the loading of Pt at the TiO2 surface, the electrocatalytic activity toward the ORR could be improved compared to that of the commercial Pt/C (E-TEK) material, even at lower Pt loadings. The enhancement in activities could be assigned to the balance between Pt loading and generation of reactive surface sites, such as adsorbed oxygenated species. Moreover, the utilization of TiO2 as support enabled improved stabilities relative to Pt/C (E-TEK). We believe that the results described herein may inspire the development of electrocatalysts for the ORR with improved activities and stabilities.

Gold nanoparticles incorporated on ceria nanowires have been employed as efficient nanocatalysts for the selective oxidation of thioanisole. The control of both physical and chemical parameters as well as metal–support interactions are important factors that determine their performances. Considering their one-dimensional morphology with large surface area, thin diameters, high concentration of oxygen vacancies, and small Au NPs uniformly on the entire CeO2 surface with a high fraction of oxidized gold species, these characteristics make them favorable nanocatalysts for oxidation transformations. The CeO2-Au nanowires displayed improved performances towards the oxidation of thioanisole when compared to the pure CeO2 nanowires and commercial CeO2-Au catalysts. The CeO2-Au nanowires catalyzed the selective synthesis of methyl phenyl sulfoxide with up to 100 % of selectivity and high conversion. The impact of solvent and temperature during the catalytic reaction was also experimentally and theoretically investigated by DFT calculations, indicating a key role in the observed activities.

Among the several classes of chemical reactions, the green oxidation of organic compounds has emerged as an important topic in nanocatalysis. Nonetheless, examples of truly green oxidations remain scarce due to the low activity and selectivity of reported catalysts. In this paper, we present an approach based on the optimization of both the support material and the active phase to achieve superior catalytic performances towards green oxidations. Specifically, our catalysts consisted of ultrasmall Au NPs deposited onto MnO2 nanoflowers. They displayed hierarchical morphology, large specific surface areas, ultrasmall and uniform Au NPs sizes, no agglomeration, strong metal-support interactions, oxygen vacancies, and Auδ+ species at their surface. These features led to improved performances towards the green oxidations of CO, benzene, toluene, o-xylene, glucose, and fructose relative to the pristine MnO2 nanoflowers, commercial MnO2 decorated with Au NPs, and other reported catalysts. We believe that the catalytic activities, stabilities, and mild/green reaction conditions described herein for both gas and liquid phase oxidations due to the optimization of both the support and active phase may inspire the development of novel catalytic systems for a wealth of sustainable transformations.

Further improvements and mechanistic understanding of the electrocatalytic enhancements towards the oxygen reduction reaction (ORR) are required to meet cost/energy demands and thus enable their practical applications in polymer electrolyte fuel cells. An investigation of the electrocatalytic enhancement mechanisms and stability of controlled electrocatalysts comprised Pt nanoparticles supported on TiO2/C materials was herein performed. The catalysts were prepared by depositing Pt, over the surface of TiO2 colloidal spheres. These materials were then supported onto Vulcan carbon to produce Pt/TiO2/C. The effect of Pt coverage at the TiO2 surface as well as the Pt/TiO2 loading on carbon over their ORR activity and stability were investigated. Results indicate that the control over Pt coverage at the surface played a pivotal role on activity optimization, in which an association between Pt content at the TiO2 surface and ORR activity was established. The ORR activity and stability were superior as compared to commercial Pt/C (E-TEK). Variations in catalytic activity could be correlated with the morphological features and with the concentration of surface reactive groups. Results described herein suggest that the understanding of the electrocatalytic enhancement mechanism together with the controlled synthesis of Pt-based nanomaterials may lead to tailored surface properties and thus ORR activities.

The localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles has been used to accelerate several catalytic transformations under visible-light irradiation. In order to fully harness the potential of plasmonic catalysis, multimetallic nanoparticles containing a plasmonic and a catalytic component, where LSPR-excited energetic charge carriers and the intrinsic catalytic active sites work synergistically, have raised increased attention. Despite several exciting studies observing rate enhancements, controlling reaction selectivity remains very challenging. Here, by employing multimetallic nanoparticles combining Au, Ag, and Pt in an Au@Ag@Pt core–shell and an Au@AgPt nanorattle architectures, we demonstrate that reaction selectivity of a sequential reaction can be controlled under visible light illumination. The control of the reaction selectivity in plasmonic catalysis was demonstrated for the hydrogenation of phenylacetylene as a model transformation. We have found that the localized interaction between the triple bond in phenylacetylene and the Pt nanoparticle surface enables selective hydrogenation of the triple bond (relative to the double bond in styrene) under visible light illumination. Atomistic calculations show that the enhanced selectivity toward the partial hydrogenation product is driven by distinct adsorption configurations and charge delocalization of the reactant and the reaction intermediate at the catalyst surface. We believe these results will contribute to the use of plasmonic catalysis to drive and control a wealth of selective molecular transformations under ecofriendly conditions and visible light illumination.

Among the several classes of chemical reactions, the green oxidation of organic compounds has emerged as an important topic in nanocatalysis. Nonetheless, examples of truly green oxidations remain scarce due to the low activity and selectivity of reported catalysts. In this paper, we present an approach based on the optimization of both the support material and the active phase to achieve superior catalytic performances towards green oxidations. Specifically, our catalysts consisted of ultrasmall Au NPs deposited onto MnO

This study demonstrates that the precursor reduction kinetics can be employed to control the morphology and composition of bimetallic metal/metal oxides systems obtained by galvanic replacement reaction using metal oxides as sacrificial templates. This work investigated Cu2O as a proof-of-concept example, in which the relative rates of Cu2O oxidation by O2 and by noble metal precursors determined the morphology and composition of the products. We focused on three metal precursors with fast, medium, and slow reduction kinetics in the presence of Cu2O under aerobic conditions: PdCl42–, AuCl4–, and Ru3+, respectively. It was found that metal-oxide-based bowls, rattles, or dendrites can be obtained by simply changing the precursor reduction kinetics. These results provide novel insights over the versatility and mechanistic understanding of galvanic replacement to the synthesis of metal/metal-oxide bimetallic nanoparticles.

In this work, we address the stability of platinum nanoparticles (Pt-NPs) encapsulated in alumina. Colloidal Pt-NPs capped with poly(N-vinyl-2-pyrrolidone) (PVP) were prepared and enclosed in an oxide matrix by incorporating them during the sol–gel synthesis of boehmite. PVP/Pt molar ratios of 0.2 and 10 produced particles with similar average diameters ( 2 O 3 ) by several techniques, showing that Pt-NPs catalyzed PVP decomposition at lower temperature than required for dehydroxylation of boehmite, causing sintering of the Pt-NPs when the PVP/Pt ratio was low. The results showed that a high PVP/Pt ratio was required to encapsulate and stabilize the Pt-NPs in the γ-Al 2 O 3 support, having a direct impact in the catalytic performance of the materials in the water gas shift reaction.

ZrO2-supported Cu catalysts with different Cu content (5–30 wt.%) were prepared by impregnation method. The effect of Cu content on the structure, surface and catalytic properties of Cu/ZrO2 catalysts in the reaction of ethanol conversion was studied. The physicochemical characterization of the calcined and reduced samples was carried out by: N2 adsorption–desorption isotherms, N2O titration, XRD, XPS, TPR and DRFTS of CO adsorption. It was observed that the increase of Cu content leads to decrease of the apparent copper metal dispersion caused by the strong agglomeration of the metal particles. The selectivity to different reaction products was connected with the electronic properties of the catalysts defined by the copper particle size and the interface at metal-oxide support. The highest selectivity to ethyl acetate over samples with Cu content ≥10 wt.% was assigned to the high density of basic sites of O2− ions and more heterogeneous distribution of copper species (Cu0/Cu+) defined by DRIFTS of CO adsorption and XPS.

Although green catalytic transformations are very attractive, they often remain limited by low conversion percentages and selectivity. Here, we demonstrate that high catalytic performances (TOF = 590,000 h −1 ) could be achieved towards the green oxidation of silanes and H 2 production under ultralow Au loadings (0.001–0.0002 mol% in terms of Au) employing H 2 O as the oxidant, 25 °C as the reaction temperature, and MnO 2 nanowires decorated with ultrasmall Au NPs (3 nm) as catalysts. In addition to these high activities towards a variety of substrates, the MnO 2 –Au NPs displayed good stability/recyclability, in which no morphological changes or loss of activity were observed even after 10 reaction cycles. The improved catalytic activities observed for the MnO 2 –Au NPs can be assigned to: (i) the metal–support interactions, in which the presence of Au NPs could facilitate oxidative processes and thus yield high performances towards the oxidation of hydrosilanes; (ii) the significant concentration of Au δ+ species and oxygen vacancies at the catalyst surface that represent highly catalytically active sites towards oxidation reactions, and (iii) the Au NPs ultrasmall sizes at the MnO 2 surface that enable the exposure of high energy Au surface/facets, high surface-to-volume ratios, and their uniform dispersion. The MnO 2 –Au NPs could be synthesized by a facile approach based on the utilization of MnO 2 nanowires as physical templates for Au deposition without any prior surface modification/functionalization steps. The utilization of supported ultrasmall Au NPs having controlled sizes and dispersion may inspire the design of novel catalysts capable of enabling high catalytic performances towards green transformations at ultralow metal loadings.

The effect of x Sm 2 O 3 addition to y CeO 2 –Al 2 O 3 -supported Pt catalysts (where x and y are the Sm 2 O 3 and CeO 2 content, respectively, giving x + y = 12 wt.%) on the surface, structure and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as N 2 adsorption–desorption isotherms, XRD, XPS, FTIR and TPR. The catalytic properties of the catalysts were evaluated in the reaction of partial oxidation of methane. The relationship between the catalytic performance and physichochemical properties of Pt/ x Sm 2 O 3 – y CeO 2 –Al 2 O 3 catalysts was evaluated. The improvement of the catalytic activity and stability observed for Sm 2 O 3 -doped CeO 2 –Al 2 O 3 -supported Pt catalysts was attributed to the increase of the platinum metallic dispersion, reducibility and oxygen storage capacity. An optimum interaction between the platinum oxide species and the total surface oxygen vacancies was observed at Sm 2 O 3 content of 3 wt.% revealed by TPR.

In this work, a simple but powerful method for controlling the size and surface morphology of AgAu nanodendrites is presented. Control of the number of Ag nanoparticle seeds is found to provide a fast and effective route by which to manipulate the size and morphology of nanoparticles produced via a combined galvanic replacement and reduction reaction. A lower number of Ag nanoparticle seeds leads to larger nanodendrites with the particles' outer diameter being tunable in the range of 45-148 nm. The size and surface morphology of the nanodendrites was found to directly affect their catalytic activity. Specifically, we report on the activity of these AgAu nanodendrites in catalyzing the gas-phase oxidation of benzene, toluene and o-xylene, which is an important reaction for the removal of these toxic compounds from fuels and for environmental remediation. All produced nanodendrite particles were found to be catalytically active, even at low temperatures and low metal loadings. Surprisingly, the largest nanodendrites provided the greatest percent conversion efficiencies.

This work describes the preparation of the iron (III) porphyrin, FeTDCNO2, entrapped in a silica matrix in the form of powder (FePD) or thin film using the sol-gel process. The films were obtained from sols using the dip-coating technique. The variables involved in the FePD preparation were analysed by a fractional factorial design with resolution 5, designated by 2 V 5 − 1. The variables which present a positive effect and maximise the loading of the studied ironporphyrin on the FePD material are solvent, water volume and reaction time. The utilization of pyridine or imidazole as template does not affect the preparation of the FePD material. The UV-visible absorption spectra of all prepared materials present the characteristic Soret band of ironporphyrins at 419–420 nm. The materials were analysed by thermogravimetric analysis, isotherm of nitrogen adsorption, 29Si NMR and scanning electron micrograph. The catalytic performance of FePD-imidazole on the epoxidation of z-cyclooctene with iodosylbenzene is similar to that of FeTDCNO2 in homogeneous solution (60 and 52%).

The optimised conditions for preparation of ironporphyrin (FeP)-template trapped silica obtained by the sol–gel process are analysed by fractional factorial design. The FeP iron 5,10,15,20-tetrakis(pentafluorophenyl)-porphyrin (FeTFPPCl), iron 5,10,15,20-tetrakis(2,6-dichlorophenyl-3-sulphonatophenyl)-porphyrin (FeTDCSPP(Na)4Cl), iron 5,10,15,20-tetrakis-p-carboxyphenylporphyrin (FeTCPP(Na)4Cl) and iron 5,10,15,20-tetrakis-p-methylpyridilporphyrin (FeTMPyP(Cl)5) were used. Pyridine or 4-phenylimidazole was used as template. Scanning electron microscopy (SEM) shows that the use of different porphyrins and conditions in the preparation of xerogel produce different product morphologies. The prepared materials have surface areas, between 300 and 1000 m2/g. The electron paramagnetic resonance spectra of trapped materials have characteristic signal of FeIII high spin, the presence of porphyrin species in a rhombic symmetry and porphyrin aggregates were also observed.

Novel hybrid organic–inorganic catalysts constituted by iron(III) or manganese(III) 5,10,15,20-tetrakis(pentafluorophenyl) porphyrin entrapped in an alumina amorphous matrix have been prepared. The hybrid materials were obtained by a non-hydrolytic sol–gel route, through the condensation of aluminium chloride with diisopropyl ether in the presence of metalloporphyrin. The presence of the metalloporphyrin entrapped in the alumina matrix is confirmed by ultraviolet–visible spectroscopy and electron spectroscopic imaging. The material was also analysed by infrared spectroscopy, selected area diffraction, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis, and its surface area was determined. Comparison between the leaching of metalloporphyrin from non-hydrolytic materials and adsorbed metalloporphyrin on commercial neutral alumina confirms that in the non-hydrolytic materials the metalloporphyrin is entrapped and not just adsorbed on the alumina surface. The use of a conventional hydrolytic sol–gel process leads to the complete leaching of the metalloporphyrin from the matrix, underlining the importance of the non-hydrolytic alumina gel process in the matrix preparation. The prepared alumina matrix materials are amorphous, even after heat treatment up 270 °C. The new catalysts prepared were tested for their ability to catalyse the epoxidation of (Z)-cyclooctene using iodosylbenzene as oxygen donor, giving high yields in the epoxidation, similar to those obtained using the metalloporphyrin in solution or supported on a silica matrix.