Heteronuclear coordination compounds of d-metals are effective precursors for the production of bimetallic nanoalloys (Plyusnin et al., 2022) [1], which, in turn, are widely used in catalysis. Catalysts based on Rh and Cu, as well as Rh and Zn, are highly active in the process of steam reforming of hydrocarbons. Double oxalates of Rh with Cu and Rh with Zn with the general formula [(C2O4)(H2O)2Rh- (mu-C2O4)-M(H2O)2-(mu-C2O4)-Rh (H2O)2(C2O4)]& sdot;6H2O (M = Cu, Zn) are synthesized and structurally characterized. According to thermogravimetric analysis, the complexes completely decompose in He and H2 atmospheres already at 300 degrees C with the formation of the corresponding nanoalloys in the Cu-Rh and Zn-Rh systems. Calcination in an O2 atmosphere leads to the formation of a mixed oxide with a spinel structure. The Cu-Rh/Ce0.75Zr0.25O2 and Zn-Rh/ Ce0.75Zr0.25O2 catalysts were prepared by impregnation by moisture capacity on a porous support followed by calcination in a hydrogen atmosphere. The obtained catalysts were tested in propane steam reforming for hydrogen production at 300-480 degrees C and WHSV = 10 000-40 000 cm3 h- 1 center dot gcat- 1. At these conditions the Cu-Rh/ Ce0.75Zr0.25O2 and Zn-Rh/Ce0.75Zr0.25O2 catalysts demonstrated high selectivity for hydrogen (more than 70 %) compared to the monometallic catalyst Rh/Ce0.75Zr0.25O2 (less than 60%). Bimetallic catalysts make it possible to increase hydrogen productivity by reducing the reaction rate of methanation of carbon oxides, which is achieved due to the presence of Cu and Zn in the catalyst structure.

The application of composite materials as catalysts for the oxidation of CO and other toxic compounds is a promising approach for air purification. In this work, the composites comprising palladium and ceria components supported on multiwall carbon nanotubes, carbon nanofibers and Sibunit were studied in the reactions of CO and CH4 oxidation. The instrumental methods showed that the defective sites of carbon nanomaterials (CNMs) successfully stabilize the deposited components in a highly-dispersed state: PdO and CeO2 nanoparticles, subnanosized PdOx and PdxCe1−xO2−δ clusters with an amorphous structure, as well as single Pd and Ce atoms, are formed. It was shown that the reactant activation process occurs on palladium species with the participation of oxygen from the ceria lattice. The presence of interblock contacts between PdO and CeO2 nanoparticles has an important effect on oxygen transfer, which consequently affects the catalytic activity. The morphological features of the CNMs, as well as the defect structure, have a strong influence on the particle size and mutual stabilization of the deposited PdO and CeO2 components. The optimal combination of highly dispersed PdOx and PdxCe1−xO2−δ species, as well as PdO nanoparticles in the CNTs-based catalyst, makes it highly effective in both studied oxidation reactions.

Herein, the highly dispersed palladium and ceria species were deposted on the surface of multi-walled carbon nanotubes (MWCNTs) by co-deposition from acetone solutions. The use of MWCNTs allowed varying Pd/Ce atomic ratio in a wide range, while maintaining a high dispersion of the active components. Application of physicochemical methods revealed the formation of various palladium species. Single Pd2+ ions dispersed in CeO2 lattice were the main Pd-Ce-Ox species at low Pdat/Ceat ratio. With an increase of the Pd content in the samples the preferential formation of PdO particles in a tight contact with CeO2 nanoparticles was observed. The size of PdO and CeO2 primary particles was in a range of 1-5 nm.The Pd-Ce-Ox/MWCNTs samples showed high activity in the CO oxidation reaction already at room tem-perature with a temperature of 50% CO conversion below 100 degrees C. The Pd2+-CeO2 and PdO-CeO2 species demonstrated the comparable activity in "dry" CO oxidation. However, the presence of water vapor in the re-action mixture resulted in the immediate deactivation of Pd2+-CeO2 species, while PdO-CeO2 species retained a high activity at 20 degrees C. The results of the work highlight the benefits of MWCNTs, Pd, and CeO2 combination for obtaining catalysts highly active in CO oxidation.

Heteronuclear coordination compounds of d-metals are suitable single-source precursors for bimetallic nanoalloys, which often show extraordinary catalytic properties due to synergetic effect. In particular, Ni- and Rh-based catalysts are highly effective in low temperature steam reforming processes. Double oxalates of Rh with Ni and Co of the formula {[Rh(H2O)(2)(C2O4)mu-(C2O4)](2)M(H2O)(2)}center dot 6H(2)O (M = Ni, Co) were synthesized and structurally characterized. According to thermogravimetric analysis, the complexes decompose completely in He and H-2 atmospheres to form corresponding nanoalloys at similar to 300 degrees C. The calcination in O-2 atmosphere leads to formation of spinel type mixed oxide. The supported Co-Rh/Al2O3 and Ni-Rh/Al2O3 catalysts were prepared by impregnation of double oxalate complexes in porous support with subsequent calcination and tested in propane low temperature steam reforming in CH4 excess. The Co-containing catalyst showed comparable activity regarding to pure Rh/Al2O3 sample, while bimetallic Ni-Rh/Al2O3 catalyst revealed to be appreciably more active, than monometallic catalysts with higher active component loadings. Rh-Ni catalyst allowed for complete propane conversion at T approximate to 350 degrees C, whereas for Rh catalyst the temperature was T approximate to 410 degrees C, and Rh-Co did not reach complete C3H8 conversion at all. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

Министерство науки и высшего образования Российской Федерации Российская академия наук Научный совет по неорганической химии РАН Научный совет по аналитической химии РАН Научный совет по химической технологии РАН Российское химическое общество имени Д.И

The composite nanomaterials based on noble metals, reducible oxides, and nanostructured carbon are considered to be perspective catalysts for many useful reactions. In the present work, multi-walled carbon nanotubes (MWCNTs) were used for the preparation of Pd-Ce-Ox/MWCNTs and Pt-Ce-Ox/MWCNTs catalysts comprising the active components (6 wt%Pd, 6 wt%Pt, 20 wt%CeO2) as highly dispersed nanoparticles, clusters, and single atoms. The application of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) provided analysis of the samples’ morphology and structure at the atomic level. For Pd-Ce-Ox/MWCNTs samples, the formation of PdO nanoparticles with an average crystallite size of ~8 nm was shown. Pt-Ce-Ox/MWCNTs catalysts comprised single Pt2+ ions and PtOx clusters less than 1 nm. A comparison of the catalytic properties of the samples showed higher activity of Pd-based catalysts in CO and CH4 oxidation reactions in a low-temperature range (T50 = 100 °C and T50 = 295 °C, respectively). However, oxidative pretreatment of the samples resulted in a remarkable enhancement of CO oxidation activity of Pt-Ce-Ox/MWCNTs catalyst at T < 20 °C (33% of CO conversion at T = 0 °C), while no changes were detected for the Pd-Ce-Ox/MWCNTs sample. The revealed catalytic effect was discussed in terms of the capability of the Pt-Ce-Ox/MWCNTs system to form unique PtOx clusters providing high catalytic activity in low-temperature CO oxidation.

New coordination compounds trans -bis(oxalato)diaquarhodiate sodium dihydrate Na[Rh(H 2 O) 2 Ox 2 ]·2H 2 O (crystallizes in two polymorphic forms NaRh-1 and NaRh-2), trans -bis(oxalato)hydroxoaquarhodiate sodium tetrahydrate Na 2 [Rh(H 2 O)(OH)Ox 2 ]·4H 2 O (Na2Rh) and trans -bis(oxalato)diaquarhodic acid tetrahydrate (H 3 O)[Rh(H 2 O) 2 Ox 2 ]·4H 2 O (HRh) are synthesized. The compounds are characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction. NaRh-1, NaRh-2 and Na2Rh crystallize in space group P 1 . Trans -bis(oxalato)diaquarhodic acid exists not only in solution, but can also crystallize as a tetrahydrate (space group C 2/ c ). The formation of various species in solution of rhodium hydroxide in oxalic acid and their redistribution were studied using 103 Rh NMR spectroscopy.

Синтезированы новые координационные соединения — тетрагидрат диоксалатопалладата цинка(II) [{Zn(H2O)3(Pd(C2O4)2)}2(μ-H2O)2]·4H2O и моногидрат диоксалатопалладата марганца(II) {(μ-C2O4)Pd(μ-C2O4)Mn(H2O)3}n·nH2O. Вещества охарактеризованы методами ИК-спектроскопии, элементного и рентгеноструктурного анализа. Кристаллографические данные для комплекса с Zn: a = 7.2812(4) Å, b = 9.0258(5) Å, c = 10.2468(6) Å, α = 81.0335(1)°, β = 80.5341(2)°, γ = 75.9627(1), пространственная группа Р–1 , Z = 2, ρвыч = 2.367 г/cм3. Кристаллографические данные для комплекса с Mn: a = 6.3605(4) Å, b = 8.8464(5) Å, c = 18.7382(1) Å, β = 98.398(2), пространственная группа P21/c, Z = 2, ρвыч = 2.607 г/cм3. Комплексы кристаллизуются в различном структурном мотиве: олигомерном в случае Zn и цепочечном в случае Mn. В обеих структурах оксалатопалладат(II) координирован терминальными атомами кислорода к неблагородному металлу.

The thermal properties of [{Zn(H2O)3(PdOx2)}2(μ-H2O)2] · 4H2O and {(μ-Ox)Pd(μ-Ox)Mn(H2O)3}n · nH2O have been studied in various atmospheres. Zinc forms the intermetallide ZnPd in inert (He) and reductive (H2) atmospheres and a ZnO–PdO oxide mixture in an oxidative (air) atmosphere. Manganese forms MnO–Pd mixtures in an inert atmosphere, experiences deeper oxidation to Mn3O4 in an oxidative atmosphere, and is partially reduced to form the intermetallide Mn3Pd5 in a reductive atmosphere. High catalytic activity in CO photooxidation has been discovered in the Zn-containing sample deposited onto a TiO2 substrate. The XAFS spectroscopy data for the model catalysts make it possible to assume the formation of nanosized palladium particles during the hydrogen reduction of supported precursors.

New inorganic compounds [M′(H2O)6][M′′(NO2)4]·2H2O (M′ = Ni, Co; M′′ = Pd, Pt) have been synthesized and used as single-source precursors for bimetallic nanoalloys.