Iron oxide-modified 1Pd0.5Fe and 1Pd10Fe catalysts with a target content of 1 wt

Cobalt nanoparticles embedded in a carbon matrix were obtained by thermolysis of glucose deposited on Co3O4/SiO2. The magnetic characteristics of the obtained nanoparticles were measured. This process formed single-domain (d < 20 nm) carbon-coated Co nanoparticles. The average size and the size distribution of Co nanoparticles depend on the amount of glucose used for the preparation. The use of a relatively small amount of glucose (glucose/cobalt < 1 mol/mol) leads to the formation of carbon shells enveloping Co nanoparticles, which are resistant to oxidation in air up to 200°C. In contrast, the use of a larger amount of glucose leads to the formation of an amorphous carbon layer with metal particles enclosed in it. Thus, the resulting nanoparticles are more susceptible to oxidation, and approximately half of the deposited cobalt is oxidized to CoO within a few days of exposure to air.

Pd/ZrO2 and Pd/ZrO2SiO2 catalysts prepared by wet impregnation and reduced with H2 under mild (30 °C, aqueous suspension) or harsh (320 °C) conditions were compared in the hydrodechlorination of the microecotoxicant diclofenac in aqueous solution at 30 оС. According to TPR and XPS data, the addition of SiO2 to the support reduces the degree of metal-support interaction and facilitates the reduction of palladium. Despite the lower Pd0 fraction, the Pd/ZrO2 catalyst was more active in the batch reactor: after reduction at 320 °С, it slightly, and after mild reduction, signi cantly (7 times) exceeded Pd/ZrO2SiO2 in catalytic activity. XRD and TEM showed a wider size distribution of palladium nanoparticles in the Pd/ZrO2 sample, while low-temperature N2 adsorption, XPS, and TPR demonstrated better accessi-bility of palladium on the Pd/ZrO2 surface due to reduced decoration with support components and increased pore size. These features explain the increased activity of Pd/ZrO2. Testing in the ow system demonstrated higher DCF conversion in the presence of catalysts reduced at 320°C and higher stability of Pd/ZrO2SiO2 compared to Pd/ZrO2. The stability is ensured by the increased reducibility of Pd2+ with H2 and by the developed surface of Pd/ZrO2SiO2, which prevents deactivation under the action of HCl released in hydrodechlorination.

A method for synthesis of nanocomposite with core–shell structure made of carbon matrices and La nanoparticles for its subsequent approbation as contrast agent in radiological studies has been proposed. The synthesis includes three stages, consisting of (1) preparation of few-layer graphite fragments (graphite nanoflakes, GNF) as carbon matrix support, (2) preparation of La-containing composite by impregnation of GNF nanoparticles with lanthanum nitrate solution with subsequent annealing and (3) surface graphitization of obtained product. All samples were studied by transmission electron microscopy, Raman and X-ray photoelectron spectroscopy. It was shown that the graphite shells contained from 2 to 3 carbon layers, and the La-containing phase was lanthanum carbonate.

Few-layer graphene nanoflakes (GNFs) containing 8–10 graphene layers were treated at temperatures of 600–1800°C and pressures of 10–50 MPa by spark plasma sintering. At 600°С, the GNF powders did not consolidate; sintering with formation of pellets occurred at 1200–1800°С. As the temperature and pressure of sintering increased, the graphite structure became improved, and the number of carbon layers increased to 15–20; all the sintered samples were mesoporous.

The influence of carbon on the genesis of the active phase of cobalt in aluminum–magnesium spinel supported catalysts on their catalytic properties in the synthesis of hydrocarbons from CO and H2 has been studied. Promotion with carbon was carried out by two independent methods: in the first one, carbon was deposited on a spinel support by thermolysis of glucose followed by the deposition of cobalt; in the second one, the catalyst was prepared by coimpregnation of the support with a solution of cobalt nitrate and glucose followed by thermolysis. The catalysts were characterized by simultaneous thermal analysis in combination with mass spectroscopy of evolved gases, in situ magnetic measurements, low-temperature nitrogen adsorption, and transmission electron microscopy. The modified catalysts showed a significantly higher CO conversion rate (turnover frequency) and selectivity for target liquid hydrocarbons compared to the unpromoted catalyst.

Covalently crosslinked 3D structures of carbon nanotubes (CNTs) and CNTs with low-layer graphene fragments (LGFs) are obtained via the hydrolysis of 3-aminopropyltriethoxysilane with oxidized CNTs and/or LGFs. The resulting samples are consolidated into non-disintegrating pellets through spark plasma sintering at 1100°C and 30 MPa. Oxygen-containing groups are eliminated, and the LGF particles are transformed into a mixture of graphene sheets and onion-like carbon nanostructures. The resulting CNT consolidates and mixtures of CNTs with LGF have densities of 0.85 and 0.81 g cm−3 and conductivities of 42 and 57 S m−1, respectively. It is shown that the consolidated samples can be oxidized with nitric acid vapor without disturbing their 3D structure. When oxidative exposure time is increased from 3 to 6 h, the content of oxygen grows from 8.4 to 15.3 at % for 3D-crosslinked CNT structures, and from 14.0 to 16.1 at % for 3D-crosslinked CNT structures with LGFs.

The effect of synthesis conditions and incorporation of heteroatoms on the structure and morphology of few-layer graphene nanoflakes is investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy. It is found that doping with nitrogen forms defects inside graphene layers, while incorporation of silicon in contrast results in their bending and the formation of interlayer defects. Increasing the synthesis temperature reduces the number of defects in the material via graphitization and increase in the number of layers.

The composition and structure of the surface phases of catalysts based on Pt, Ni, and Cr (platinum, bi- and trimetallic) supported on a Sibunit carrier are studied via TEM and EDS. The structure of the catalysts before and after reductive hydrogenation are compared. It is found that the metal in the Pt/C system is in a highly dispersed state, mainly in an oxidized form. In bimetallic and ternary catalysts, the surface contains metallic and oxide components; on the surface of Pt–Ni catalyst, the metal phase is more pronounced than with Ni–Cr and Pt–Ni–Cr. Nickel-based catalysts contain large metal particles (up to 30 nm). After reductive hydrogenation, an increase in dispersion and a reduction in the crystallinity of metal particles is observed in all of the studied systems.

The work is devoted to the development of hybrid materials for medical hyperthermy based on carbon nanotubes (CNTs) modified in their internal channels by perovskite-like manganites. It is shown that phases are formed in preliminarily opened channels of tubes from precursors: salts, manganese, strontium, calcium and lanthanum carbonates and oxides. High-resolution transmission electron microscopy reveals fine crystalline particles of complex oxide phases inside the CNTs, and reflections corresponding to the temperature of the solid-phase synthesis of manganites are found on the calorimetric dependences.