Nanocomposites SnO2/SiO2 with a silicon content of [Si]/([Sn] + [Si]) = 3/86 mol.% were obtained by the hydrothermal method. The composition and microstructure of the samples were characterized by EDX, XRD, HRTEM and single-point Brunauer-Emmet-Teller (BET) methods. The surface sites were investigated using thermal analysis, FTIR and XPS. It is shown that the insertion of silicon dioxide up to the value of [Si]/([Sn] + [Si]) = 19 mol.% stabilizes the growth of SnO2 nanoparticles during high-temperature annealing, which makes it possible to obtain sensor materials operating stably at different temperature conditions. The sensor properties of SnO2 and SnO2/SiO2 nanocomposites were studied by in situ conductivity measurements in the presence of 10–200 ppm CO in dry and humid air in the temperature range of 150–400 °C. It was found that SnO2/SiO2 nanocomposites are more sensitive to CO in humid air as compared to pure SnO2, and the sample with silicon content [Si]/([Sn] + [Si] = 13 mol.% is resistant to changes in relative air humidity (RH = 4%–65%) in the whole temperature range, which makes it a promising sensor material for detecting CO in real conditions. The results are discussed in terms of the changes in the composition of surface-active groups, which alters the reactivity of the obtained materials.
A series of salts (R 4 N) 2 [Pd(NO 3 ) 4 ] (R = CH 3 , C 2 H 5 , n-C 3 H 7 ; 1−3) were synthesized in high yield from a nitric acid solution of palladium. The salts were characterized by a combination of physicochemical methods, and their crystal structures were determined by X-ray diffraction. The conformation of the [Pd(NO 3 ) 4 ] 2− anion was studied in detail using crystal structure data and density functional theory calculations. A combination of nonhygroscopicity and stability under normal conditions, together with thermolability, high solubility in various solvents, and the lability of nitrato ligands, makes salts 1−3 valuable starting materials for the synthesis of Pd compounds and the preparation of Pd-containing catalysts. In this work, these applications were illustrated by the synthesis of heteroleptic Pd(II) nitrato complexes with N-donor ligands and the preparation of Pd 0.1 Ni 0.9 / SiO 2 catalysts, which worked well in H 2 generation from hydrazine hydrate. Generally, it was shown that up to several weight percent of Pd can be deposited on various oxide/hydroxide supports using a straightforward chemisorption procedure from acetone solutions of 1−3.
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