The CO oxidation pattern of a nanocomposite MnCeOx catalyst (M5C1; Mnat/Ceat, 5) in the range of 293–533 K (P, 1 atm) has been probed under a kinetic regime, varying reagent pressure (pCO0, ...0.01–0.025 atm; λ0, 1), Formula Omitted ratio (λ0, 0.25–4.0) and CO2 co-feeding (0.05–0.10 atm). Activity data indicate fractional orders on pCO (0.6 ± 0.1) and pO2 (0.4 ± 0.1), with an activation energy of 40 ± 3 kJ mol−1, and a negative kinetic effect of CO2 co-feeding due to competitive adsorption processes. Coupled with systematic evidence on the reactivity and mobility of catalyst oxygen and surface intermediates, kinetic data disclose a concerted redox mechanism of Langmuir–Hinshelwood type, which starts by abstraction of O-atoms from surface active MnIV centres (r.d.s.), and is sustained by adsorption of diatomic oxygen species on O-vacancies. The derivative and integral forms of the formal rate equation explain the empirical kinetics, predicting the activity pattern of the MnCeOx catalyst in the range of 293–533 K.
The direct conversion of untreated microcrystalline cellulose into C
-C
alcohols, through a one-pot process promoted by the heterogeneous bimetallic Pd/Fe
O
catalyst, is presented. The process is ...selfsustainable without the addition of external molecular hydrogen or acid/basic promoters and is mainly selective toward ethanol. At 240 °C, a complete cellulose conversion was reached after 12 h with an ethanol molar selectivity of 51% among liquid products. The synergistic effect played by water (which aids in the chemical pretreatment means of cellulose through the hydrolysis process) and the Pd/Fe
O
catalyst (which catalyzes the hydrogenolysis reaction driving the pattern of obtained products) is elucidated.
The majority of artificial joints incorporate biomedical grade Ultra High Molecular Weight Poly Ethylene (UHMWPE), whose wear is considered most important in controlling service time of the whole ...joint. The aim of this work was to improve wear resistance of UHMWPE through the addition of 0.5–2.0wt% of Carbon Nano Filler (CNF) and 2% wt of Paraffin Oil (PO) using ball milling (BM) and extrusion techniques (EX). The wear tests on these nanocomposites were conducted by a pin on disc in dry (air) and wet media (simulated synovial fluid or artificial lubricant, and bovine synovial fluid or natural lubricant). Mechanical tests (tensile and hardness), physical analysis (calorimetric, density, wet ability, roughness) and morphological observations were also performed. The experimental results showed that natural lubricant provides the greatest reduction in wear rate while the largest one occurred in air. Furthermore, the BM mixed nanocomposites with a filler load of 1.0% exhibited the best wear resistance among all the samples with an improvement of 42%, 64% and 83% in air, artificial and natural lubricant, respectively. This is due to its higher ductility and thermal features, and lower wet ability in the two lubricants.
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•The nanocomposites were based on biomedical UHMWPE, oil and carbon nanofiller.•UHMWPE was mixed with CNF by ball milling and extrusion.•Wear behaviour and wet ability tests were performed with or without lubricant.•The nanocomposites mixed by ball milling exhibited the best wear resistance.•The 1.0wt% of filler was optimal load for both mechanical and physical behaviour.
The CO oxidation pattern of a nanocomposite MnCeO x catalyst (M5C1; Mn at /Ce at , 5) in the range of 293–533 K ( P , 1 atm) has been probed under a kinetic regime, varying reagent pressure ( p 0CO, ...0.01–0.025 atm; λ 0 , 1), ratio ( λ 0 , 0.25–4.0) and CO 2 co-feeding (0.05–0.10 atm). Activity data indicate fractional orders on p CO (0.6 ± 0.1) and p O2 (0.4 ± 0.1), with an activation energy of 40 ± 3 kJ mol −1 , and a negative kinetic effect of CO 2 co-feeding due to competitive adsorption processes. Coupled with systematic evidence on the reactivity and mobility of catalyst oxygen and surface intermediates, kinetic data disclose a concerted redox mechanism of Langmuir–Hinshelwood type, which starts by abstraction of O-atoms from surface active Mn IV centres (r.d.s.), and is sustained by adsorption of diatomic oxygen species on O-vacancies. The derivative and integral forms of the formal rate equation explain the empirical kinetics, predicting the activity pattern of the MnCeO x catalyst in the range of 293–533 K.
Electrochemical sensors for monitoring biochemical substances are attracting considerable attention. These devices are usually based on enzymes that are sensitive and very specific. Still, the ...activity of those enzymes is lost with changes in temperature or pH. Non-enzymatic electrochemical sensors – fabricated via the modification of the electrode surface with metal oxide nanoparticles – are an ideal answer to address that problem. In this study, we investigated the photo-electrochemical properties of CuO–TiO2 heterojunctions for glucose sensing in alkaline media. A combination of high-resolution (scanning) transmission electron microscopy, spatially resolved electron energy-loss spectroscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction, was used to study in detail the microstructures of the prepared specimens. These results highlighted the strong intertwining between the TiO2 nanoparticles and the Cu-based nanoparticles, which present a metallic core with a CuO rich surface. In addition, we showed that CuO, joint to TiO2, has smaller size compared to pure CuO, which entails larger specific surface area available for the glucose electro-oxidation, which consequently enhanced the electrochemical features. The influence of Cu loading over the sensing performance of TiO2 was examined in detail carrying out electrochemical sensing tests under dark, laboratory and halogen lamp irradiation conditions. Results demonstrated that, under halogen lamp irradiation, modified CuO–TiO2 electrodes showed a specific response signal that is four times higher than that of pure CuO. Those increased photo-electrochemical properties in CuO–TiO2 heterojunctions are likely due to a synergistic effect between the microstructural characteristics and effective separation of photo-generated excitons created at the heterojunction interface. Results of this study offer applicable guidelines for designing photo-electrochemical screen-printed electrodes based on nano-sized CuO on titania for efficient detection of glucose.
The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated under mild reaction conditions, using water as the reaction medium and Pd/Fe as the catalyst. The experiments, in ...the presence of added H
2
or under inert atmosphere, clearly show that the dehydration/hydrogenation route is the key step in the case of C-O bond cleavage (hydrogenolysis) while dehydrogenation is a prerequisite for C-C bond breaking (APR), with the latter favoured at higher reaction temperatures. The temperature dependence of the C-C and C-O bond rupture is discussed by taking into account the bond energies involved in the competitive hydrogenolysis and APR reactions. Finally, the Pd/Fe catalyst was also tested in the hydrogenolysis and APR of ethylene glycol in the same temperature range, with the aim of clarifying the selective cleavage of C-O and C-C bonds in biomass derived C
2
-C
3
polyols.
The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated using Pd/Fe as the catalyst. At 180 °C, the C-O bond is preferentially cleaved while C-C bond breaking is favoured at higher reaction temperatures.
The hydrogenolysis and the aqueous phase reforming of glycerol have been investigated under mild reaction conditions, using water as the reaction medium and Pd/Fe as the catalyst. The experiments, in ...the presence of added H sub(2) or under inert atmosphere, clearly show that the dehydration/hydrogenation route is the key step in the case of C-O bond cleavage (hydrogenolysis) while dehydrogenation is a prerequisite for C-C bond breaking (APR), with the latter favoured at higher reaction temperatures. The temperature dependence of the C-C and C-O bond rupture is discussed by taking into account the bond energies involved in the competitive hydrogenolysis and APR reactions. Finally, the Pd/Fe catalyst was also tested in the hydrogenolysis and APR of ethylene glycol in the same temperature range, with the aim of clarifying the selective cleavage of C-O and C-C bonds in biomass derived C sub(2)-C sub(3) polyols.
The catalytic properties of Pt supported on zeolite P (ZP)-based materials for the preferential CO oxidation in hydrogen atmosphere under mild conditions (from room temperature to 150 °C), have been ...investigated. Pt catalysts (1–4 wt%) supported on a zeolitized pumice support (Z-PM) have been prepared. A series of bimetallic Pt–Fe on ZP, having 2 wt% Pt and different Fe loading (0.5–4 wt%), have been also prepared and used as model catalysts. A detailed characterization of the catalysts has been carried out by means of surface area and porosity measurements, X-ray diffraction, scanning electron microscopy and transmission electron microscopy in order to investigate the morphological and microstructural properties of both support and catalytic system. Pt/Z-PM exhibited complete CO conversion with 55 % selectivity at temperatures as low as 50 °C, with no noticeable degradation of the catalytic performances, indicating that the Fe content present as an impurity in the zeolitized pumice support allows to obtain catalysts characterized by high activity and stability. On the basis of the characterization and kinetic tests, hypotheses on the role of Fe promoter have been formulated.
Electrochemical sensors for monitoring biochemical substances are attracting considerable attention. These devices are usually based on enzymes that are sensitive and very specific. Still, the ...activity of those enzymes is lost with changes in temperature or pH. Non-enzymatic electrochemical sensors – fabricated via the modification of the electrode surface with metal oxide nanoparticles – are an ideal answer to address that problem. In this study, we investigated the photo-electrochemical properties of CuO–TiO 2 heterojunctions for glucose sensing in alkaline media. A combination of high-resolution (scanning) transmission electron microscopy, spatially resolved electron energy-loss spectroscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction, was used to study in detail the microstructures of the prepared specimens. These results highlighted the strong intertwining between the TiO 2 nanoparticles and the Cu-based nanoparticles, which present a metallic core with a CuO rich surface. In addition, we showed that CuO, joint to TiO 2 , has smaller size compared to pure CuO, which entails larger specific surface area available for the glucose electro-oxidation, which consequently enhanced the electrochemical features. The influence of Cu loading over the sensing performance of TiO 2 was examined in detail carrying out electrochemical sensing tests under dark, laboratory and halogen lamp irradiation conditions. Results demonstrated that, under halogen lamp irradiation, modified CuO–TiO 2 electrodes showed a specific response signal that is four times higher than that of pure CuO. Those increased photo-electrochemical properties in CuO–TiO 2 heterojunctions are likely due to a synergistic effect between the microstructural characteristics and effective separation of photo-generated excitons created at the heterojunction interface. Results of this study offer applicable guidelines for designing photo-electrochemical screen-printed electrodes based on nano-sized CuO on titania for efficient detection of glucose.
Electrochemical sensors for monitoring biochemical substances are attracting considerable attention. These devices are usually based on enzymes that are sensitive and very specific. Still, the ...activity of those enzymes is lost with changes in temperature or pH. Non-enzymatic electrochemical sensors - fabricated
via
the modification of the electrode surface with metal oxide nanoparticles - are an ideal answer to address that problem. In this study, we investigated the photo-electrochemical properties of CuO-TiO
2
heterojunctions for glucose sensing in alkaline media. A combination of high-resolution (scanning) transmission electron microscopy, spatially resolved electron energy-loss spectroscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction, was used to study in detail the microstructures of the prepared specimens. These results highlighted the strong intertwining between the TiO
2
nanoparticles and the Cu-based nanoparticles, which present a metallic core with a CuO rich surface. In addition, we showed that CuO, joint to TiO
2
, has smaller size compared to pure CuO, which entails larger specific surface area available for the glucose electro-oxidation, which consequently enhanced the electrochemical features. The influence of Cu loading over the sensing performance of TiO
2
was examined in detail carrying out electrochemical sensing tests under dark, laboratory and halogen lamp irradiation conditions. Results demonstrated that, under halogen lamp irradiation, modified CuO-TiO
2
electrodes showed a specific response signal that is four times higher than that of pure CuO. Those increased photo-electrochemical properties in CuO-TiO
2
heterojunctions are likely due to a synergistic effect between the microstructural characteristics and effective separation of photo-generated excitons created at the heterojunction interface. Results of this study offer applicable guidelines for designing photo-electrochemical screen-printed electrodes based on nano-sized CuO on titania for efficient detection of glucose.
Glucose sensing is promoted by halogen lamp photo-activation in CuO-TiO
2
heterojunctions.
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