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In this work, ceria-based nanocatalysts mixed with copper and manganese were studied. All the catalysts were synthesized via the hydrothermal procedure. Four samples were prepared here denoted through the atomic ratios of the metals in the mixed oxide: Ce0.95Mn0.05, Ce0.95Cu0.05, Ce0.95Mn0.025Cu0.025 and CeO2. The samples were tested for the CO and soot oxidation reactions with different gas-phase oxygen concentrations (10, 1.0, 0.5 and 0.02 vol% O2). As a whole, the most promising catalysts for the CO oxidation reaction are the Ce0.95Cu0.05 and Ce0.95Mn0.025Cu0.025 samples. Indeed, the presence of Cu species in the solid enhances the surface redox mechanism for the CO oxidation. High vol% O2 values lead to competitive CO and O2 adsorption on the catalyst surface thus reducing the catalytic performances for binary and ternary oxides. On the other hand, the CO oxidation reaction over the CeO2 catalyst appears favored with 10 vol% O2. For the soot oxidation reaction, the most active catalyst (in terms of soot conversion %) is the CeO2 sample likely due to the unique feature of presenting well-defined and highly reactive nanocubic structures. Moreover, the presence of 10 vol% O2 in the mixture appears to be the best condition to oxidize the soot particles.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Ceria-based catalysts doped with manganese and copper were obtained via the hydrothermal synthesis. Four systems were synthesized: CeO (pure ceria), CeMn (Mn/Ce at. ratio = 1/19), CeCu (Cu/Ce at. ratio = 1/19) and CeMnCu (Mn/Cu/Ce at. ratio = 1/1/38). The catalytic activity of the prepared materials was tested for the CO and soot oxidations. Complementary techniques (XRD, N physisorption at − 196 °C, FESEM, XPS, Raman spectroscopy, CO-TPR and Soot-TPR) were performed to investigate their physico-chemical properties. The samples were characterized by nanocubes, in the case of CeO, and by nanopolyhedra for binary (CeMn and CeCu) and ternary oxides (CeMnCu). The CO-TPR analysis has confirmed that the reducibility follows the order: CeO < CeMn < CeMnCu < CeCu. A similar trend appears for the surface defective sites (Raman spectroscopy). These findings suggest the beneficial role of dopants in improving the structural defects and the surface reducibility of ceria. Both properties promote the CO oxidation activity. In fact, the CeCu was the most effective catalyst for the CO oxidation. The CeMn sample exhibited the best performance in soot oxidation. The following order was achieved: CeMnCu < CeCu < CeO ≈ CeMn, in agreement with the reduction profiles obtained by the Soot-TPR above 400 °C. Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this work, the co-immobilization of formate dehydrogenase (FDH) and glycerol dehydrogenase (GlyDH) enzymes is proposed to reduce CO 2 into formic acid, an important chemical intermediate. The reduction of carbon dioxide is carried out by FDH to obtain formic acid, simultaneously, the GlyDH regenerated the nicotinamide cofactor in the reduced form (NADH) by the oxidation of glycerol into dihydroxyacetone. Natural zeolite was selected as immobilization support given its good properties and low cost. The natural zeolite was modified with subsequent acid-alkaline attacks to obtain a mesostructurization of the clinoptilolite. The two enzymes were co-immobilized on clinoptilolite, previously hetero-functionalized with amino and glyoxyl groups. The distribution of the enzymes was confirmed by fluorescence microscopy analysis. Furthermore, a great increase in the retained activity for the formate dehydrogenase enzyme was noted, passing from 18% to 89%, when the mesostructured clinoptilolite was used as support. The immobilization yield of formate dehydrogenase and glycerol dehydrogenase is around 100% with all the supports studied. The promising results suggest a possible development of this procedure in enzyme immobilization and biocatalysis. The biocatalysts were characterized to find the optimal pH and temperature. Furthermore, a thermal stability test at 50 °C was carried out on both enzymes, in free and immobilized forms. Finally, it was shown that the biocatalyst is effective in reducing CO 2 , both by using the cofactor in the reduced form (NADH) or the oxidized form (NAD + ), obtaining NADH through the regeneration with glycerol in this latter case., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The aim of this work is to study the activity of novel TiO 2 -based photocatalysts doped with either phosphorus or zirconium under a UV-Vis source. A set of mesoporous catalysts was prepared by the direct synthesis: TiO 2 &#95;A and TiO 2 &#95;B (titanium oxide synthesized by two different procedures), P-TiO 2 and Zr-TiO 2 (binary oxides with either nonmetal or metal into the TiO 2 framework). Complementary characterizations (N 2 physisorption at 77 K, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, X-ray Photoelectron Spectroscopy (XPS), and (DR)UV-Vis spectroscopy) were used to investigate the physicochemical properties of the prepared catalysts. Then, the photocatalysts were tested for the oxidation of propylene and ethylene under UV-Vis light. As a result, the most promising catalyst for both the propylene and ethylene oxidation reactions was the P-TiO 2 (propylene conversion = 27.8% and ethylene conversion = 13%, TOS = 3 h), thus confirming the beneficial effect of P-doping into the TiO 2 framework on the photocatalytic activity.