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An oxalate complex of vanadyl(IV) (Bu4N)2[VO(C2O4)2] (I) was synthesized and used as a vanadium precursor. The synthesis and characterization of the double complex salts [Pt(NH3)4][VO(H2O)(C2O4)2]·2H2O (III) and {[Pt(NH3)4][VO(C2O4)2]}n (IV) were carried out. The complexes obtained were characterized by IR and diffuse reflectance spectroscopy, single-crystal and powder X-ray diffraction, and EPR. The magnetic properties of I, III, and IV were also studied. The process of thermal decomposition of the synthesized complexes in reducing and inert atmospheres was studied, and the composition of the released gases was determined. Thermal decomposition of the salts in a hydrogen atmosphere at 600 °C resulted in the formation of a bimetallic solid solution, Pt0.6V0.4. [ABSTRACT FROM AUTHOR]

The controllable synthesis of carbon nanofibers (CNF) and composites based on CNF (Metals/CNF) is of particular interest. In the present work, the samples of CNF were produced via ethylene decomposition over Co-Pt (0–100 at.% Pt) microdispersed alloys prepared by a reductive thermolysis of multicomponent precursors. XRD analysis showed that the crystal structure of alloys in the composition range of 5–35 at.% Pt corresponds to a fcc lattice based on cobalt (Fm-3m), while the CoPt (50 at.% Pt) and CoPt3 (75 at.% Pt) samples are intermetallics with the structure P4/mmm and Pm-3m, respectively. The microstructure of the alloys is represented by agglomerates of polycrystalline particles (50–150 nm) interconnected by the filaments. The impact of Pt content in the Co1−xPtx samples on their activity in CNF production was revealed. The interaction of alloys with ethylene is accompanied by the generation of active particles on which the growth of nanofibers occurs. Plane Co showed low productivity (~5.5 g/gcat), while Pt itself exhibited no activity at all. The addition of 15–25 at.% Pt to cobalt catalyst leads to an increase in activity by 3–5 times. The maximum yield of CNF reached 40 g/gcat for Co0.75Pt0.25 sample. The local composition of the active alloyed particles and the structural features of CNF were explored. [ABSTRACT FROM AUTHOR]

A simple and convenient procedure for the production of highly dispersed porous Co-Pt alloys to be used as catalysts for the synthesis of nanostructured carbon fibers (CNF) has been developed. The technique is based on the thermal decomposition of specially synthesized multicomponent precursors in a reducing atmosphere. A series of porous single-phase alloys Co-Pt (10–75 at% Pt) have been synthesized. The alloys containing 75 and 50 at% Pt were identified by the x-ray diffraction analysis as the intermetallics CoPt3 and CoPt, respectively. Within the region of 10–35 at% Pt, the synthesized alloys are represented by Co1−xPtx random solid solutions with face-centered cubic lattice. The alloys obtained are characterized by a porous structure consisting of assembled fragments with a size of 50–150 nm. The obtained alloys were tested in the catalytic chemical vapor deposition of the ethylene to CNF. A significant synergistic effect between Co and Pt in the synthesis of carbon nanomaterials (CNMs) was revealed. The yield of CNF (for 30 min reaction) for catalysts containing 25–35 at% Pt was 30–38 g(CNF)/g(cat), whereas those for Co (100%) and Pt (100%) samples were as low as 5.6 and >0.1 g(CNF)/g(cat), respectively. The produced CNM composed of fibers with a segmented structure was shown to be characterized by a rather high specific surface area (200–250 m2 g−1) and structural homogeneity. [ABSTRACT FROM AUTHOR]

Thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6] in reductive and inert atmospheres has been investigated in situ using quick-EXAFS and temperature-resolved powder X-ray diffraction. For the first time, (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] have been proven as intermediates of thermal decomposition of (NH4)3[IrCl6]·H2O, (NH4)2[IrCl6] and (NH4)2[IrBr6]. Thermal degradation of (NH4)2[IrCl6] and (NH4)2[IrBr6] is a more complex process as suggested previously and includes simultaneous formation of (NH4)2[Ir(NH3)Cl5] and (NH4)2[Ir(NH3)Br5] intermediates mixed with metallic iridium. In the inert atmosphere, complexes (NH4)[Ir(NH3)2Cl4] and (NH4)[Ir(NH3)2Br4] as well as [Ir(NH3)3Br3] were proposed as possible intermediates before formation of metallic iridium particles. [ABSTRACT FROM AUTHOR]

The expediency of capillary zone electrophoresis application in the study of a mixture of rhodium(III) hydroxocomplexes is shown for the species formed during the thermal treatment of [Rh(OH)6]3− at 60 °C in alkaline media. As these compounds are unstable in solution because of polycondensation at pH > 10 and the formation of insoluble rhodium(III) hydroxides at pH 5–10, their acidic derivatives with terminal aqua ligands acted as the objects of the study. Optimal separation conditions were achieved using sodium perchlorate as a background electrolyte, a voltage of +20 kV and pH 2.6. Rhodium(III) species with different nuclearities were identified in accordance with their UV spectra and the regularities of electrophoretic migration in the capillary. The presence of a dimer was also verified by the spiking of the mixture under investigation with a previously synthesised complex [Rh2(μ-OH)2(H2O)8](NO3)4, which confirms the correct identification. [ABSTRACT FROM AUTHOR]

A series of highly soluble double complex salts [M′(H2O)6][M′′(NO2)4]·2H2O (M′ = Ni, Co; M′′ = Pd, Pt) have been synthesized, studied and used as single-source precursors for bimetallic nanoalloys and metal–oxide composites. According to the results of simultaneous thermal analysis-mass spectrometry (STA-MS), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), thermolysis of the compounds in diverse atmospheres (O2, He, and H2), delafossite-type mixed oxides M′′CoO2/(NiO + M′′O), metal–oxide composition M′O + M′′ and bimetallic solid solution M′0.5M′′0.5, respectively. In an H2 atmosphere an instant isolation of the equiatomic solid solution occurs at lower than 200 °C with simultaneous reduction of noble and ignoble metals. The bimetallic products can be superstructurally ordered at higher temperatures. The solubility of precursors in organic solvents allows carrying out an impregnation of the salts inside multiwalled carbon nanotubes; subsequent heating in H2 yields intercalated nanoparticles of ∼2–4 nm in size. [ABSTRACT FROM AUTHOR]

A new approach based on a combination of synchrotron radiation techniques, such as X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES), and powder X-ray diffraction (PXRD), has been applied to in situ study the processes of thermal decomposition of inorganic compounds and the formation of bimetallic nanoalloys. As an example, a double complex salt, [Pd(NH3)4][PtCl6], was selected because of (i) its sufficiently complicated structure and previous studies conducted via thermal analysis, ex situ PXRD and XPS, and (ii) its use as a prospective single-source precursor for the preparation of bimetallic (PdPt) nanoparticles or nanoalloys. The differences between the mechanisms based on ex situ and in situ data have been discussed for the first time. It has been found that the first step of thermal decomposition is related to the formation of crystalline [Pd(NH3)2Cl2][Pt(NH3)2Cl4]. Further decomposition results in the formation of {PdCl2}, {PtCl2}, and (NH4)2[PtCl6] in the second step. In the final step, the intermediates are completely reduced, and a bimetallic nanoalloy is formed. The different means of Pd and Pt reduction on the surface and in the bulk result in the formation of a disordered nanoalloy with possible monometallic inclusions. Further heating orders the nanoalloy that is accompanied by a decrease in the positive charge on Pt. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD) pattern of nanosized equimolar solid solution CoIr prepared by thermolysis of [Co(NH3)6][Ir(C2O4)3] contains peaks characteristic of both face-centered cubic (fcc) and hexagonal close-packed (hcp) structure. Moreover, 101 peak of hcp modification is substantially wider than 100 and 002 peaks, 102 and 103 are very broad and almost invisible. Peak 200 of fcc structure is wider than the other peaks of this modification and slightly shifted toward lower angles. It was shown by simulation of XRD patterns that particles of CoIr alloy are nanoheterogeneous and consist of lamellar domains having fcc and hcp structures. The best fit was obtained for the following model parameters: an average crystallites size is about 10 nm, average thicknesses of the fcc and hcp domains are 1.7 and 1.1 respectively. The presence of domain structure was confirmed by transmission electron microscopy data. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Pd (5%) single-phase alloy was used as a catalyst for CCVD of C 2 H 4 Cl 2. • Joint catalytic processing of C 2 H 4 Cl 2 and CH 3 CN into N-doped CNF was studied. • By XPS, produced N-CNF material contains 1.4–2.2 wt.% of structural nitrogen. • Obtained N-doped carbon filaments have regular segmental structure. • The produced N-doped CNF is characterized by S BET ∼ 390−450 m2/g, V pore ∼ 0.6 cm3/g. A single-phase micro-disperse Ni-Pd (5 wt.%) alloy prepared by coprecipitation technique was studied as a catalyst precursor for the synthesis of the nanostructured carbon product. Catalytic synthesis of N-doped carbon nanofibers was implemented by the joint decomposition of C 2 H 4 Cl 2 and CH 3 CN vapors in H 2 excess at 600 °C. The in situ kinetic experiments performed in a flow gravimetric setup with McBain balances showed that the carbon deposition process is characterized by an induction period (18−20 min). The intensive metal dusting of the Ni-Pd alloyed precursor in reaction conditions was found to lead to its complete disintegration. The obtained submicron-sized Ni-Pd particles were shown by XRD to have the same composition as the starting Ni-Pd (5%) precursor. The growth of carbon filaments accompanied the rapid disintegration of Ni-Pd alloy. The addition of acetonitrile vapors into the reaction mixture was found to enhance carbon yield from 24 (0%) to 40.5 (5 vol.%) and 50.9 (8 vol.%) grams per 1 g of catalyst for 2 h of reaction. Joint catalytic processing of C 2 H 4 Cl 2 and CH 3 CN was shown to be sufficient for the production of carbon nanofibers doped with nitrogen. According to XPS and EDX data, the average amount of nitrogen within the obtained N-CNF was about 1.8 wt.%. It was revealed by microscopic studies (SEM, TEM) that the produced N-doped carbon filaments are characterized with a rather regular segmental structure similar to that observed for a reference sample of N-free CNF. The synthesized N-CNF samples are characterized by I D /I G ∼ 1.3 (Raman spectroscopy) and high textural parameters (S BET ∼ 390−450 m2/g, V pore ∼ 0.6 cm3/g). [ABSTRACT FROM AUTHOR]

A new approach based on a combination of synchrotron radiation techniques, such as X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES), and powder X-ray diffraction (PXRD), has been applied to in situ study the processes of thermal decomposition of inorganic compounds and the formation of bimetallic nanoalloys. As an example, a double complex salt, [Pd(NH3)4][PtCl6], was selected because of (i) its sufficiently complicated structure and previous studies conducted via thermal analysis, ex situ PXRD and XPS, and (ii) its use as a prospective single-source precursor for the preparation of bimetallic (PdPt) nanoparticles or nanoalloys. The differences between the mechanisms based on ex situ and in situ data have been discussed for the first time. It has been found that the first step of thermal decomposition is related to the formation of crystalline [Pd(NH3)2Cl2][Pt(NH3)2Cl4]. Further decomposition results in the formation of {PdCl2}, {PtCl2}, and (NH4)2[PtCl6] in the second step. In the final step, the intermediates are completely reduced, and a bimetallic nanoalloy is formed. The different means of Pd and Pt reduction on the surface and in the bulk result in the formation of a disordered nanoalloy with possible monometallic inclusions. Further heating orders the nanoalloy that is accompanied by a decrease in the positive charge on Pt. [ABSTRACT FROM AUTHOR]

The platinum–gold alloyed nanoparticles were prepared via decomposition of double complex salts containing both inorganic and organic ligands. Decomposition of the precursor was performed in a reductive atmosphere with varied temperature ramping rates. The samples were characterized by means of X-ray diffraction (XRD) analysis, transmission electron microscopy, and UV–vis spectroscopy. According to XRD data, both the ramping rate and the final temperature of decomposition strongly affect the Pt–Au ratio in alloyed nanoparticles which are being formed. The average crystallite size was found to be 15–20 nm, that was also confirmed by UV–vis spectroscopy for the alloyed Pt–Au nanoparticles supported on alumina. [ABSTRACT FROM AUTHOR]

Highlights: [•] [Pd(NH3)4]MoO4 as a precursor for Pd–Mo-containing catalysts. [•] Different products are formed depending on atmosphere of thermal decomposition. [•] Thermolysis in He atmosphere affords finely mixed two-phase nanosized system Pd–MoO2. [•] Pd–MoO2 system can be a promising catalyst both in pure and supported form. [Copyright &y& Elsevier]

Abstract: A series of 1.8wt.% PdAu/γ-Al2O3 catalysts with a mean metal particle size of more than 10nm and different Pd/Au ratios were prepared by impregnation followed by hydrazine reduction and tested in the decomposition of vapour phase formic acid (2.2vol.%, 1bar) with and without added CO to the gas mixture. The catalytic activity was correlated with the bulk (AAS, XRD, EDS/TEM) and surface (XPS) composition of PdAu particles. A novel result was obtained that the surface composition of the particles did not change despite a considerable variation of the Au atomic fraction and it was found to be close to that of the Pd2Au alloy. The activity of the Au/Al2O3 catalyst was negligible compared with that of the Pd/Al2O3 catalyst being a factor of 65 lower per gram of metal at 403K. The surface electronic properties (XPS) and the catalytic activity of the Pd2Au layer calculated per one surface Pd atom (TOF) did not depend on the bulk composition of the metal particles. A lower activity of the Pd2Au layer as compared with the pure Pd layer (2–3 times) was observed, but the activation energies for the Pd and PdAu catalysts were similar (40kJmol−1) and were lower than that for the Au/Al2O3 catalyst (62kJmol−1). Addition of CO led to a considerable inhibition of the reaction for all PdAu catalysts, this being accompanied by an increase in the activation energy to 69kJmol−1. [Copyright &y& Elsevier]

Abstract: Palladium gold alloy powder (PdAu2) was synthesized by reduction of the [Pd(NH3)4][AuCl4]2 complex with H2 at 90°C, and then was additionally heated in a C2H4 (PdAu2–C x ) or H2 flow (PdAu2–H2) at 300°C. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and by a set of electrochemical methods. The Pd:Au ratio on the surface of the PdAu2 alloy suffers marginal changes after heating under C2H4 atmosphere, and decreases as a result of heating in a H2 flow. Hydrogen oxidation reaction (HOR) over the catalysts was studied using rotating disk electrode at 25°C in 0.1M HClO4 in pure H2 and in the presence of 1100ppm of CO. Heat-treatment of the PdAu2 alloy under H2 does not improve its HOR activity and CO tolerance (normalized to Pd and total metal surface area), while the PdAu2–C x catalyst exhibits substantially enhanced catalytic performance in the HOR both in the absence and in the presence of CO as compared to the parent PdAu2 alloy. The enhanced activity of the C2H4-treated PdAu2 alloy is explained by the promoting action of carbon atoms incorporated into the alloy structure during treatment under C2H4 atmosphere. This supposition is approved by the fact that mild oxidative treatment of the PdAu2–C x sample degrades notably its catalytic activity. [Copyright &y& Elsevier]

Abstract: Permanganate salt of the complex cation trans-[Rh(γ-Pic)4Cl2]+ (γ-Pic=γ-picoline) was synthesized. The unusual decomposition reaction of the salt was studied at room temperature. This process has been found to conserve the γ-picoline ligands in cation untouched. A number of transformations in anionic part of salt have been observed. Metallic products of the salt thermal decomposition have been studied. [Copyright &y& Elsevier]

The expediency of capillary zone electrophoresis application in the study of a mixture of rhodium(iii) hydroxocomplexes is shown for the species formed during the thermal treatment of [Rh(OH) 6 ] 3- at 60 °C in alkaline media. As these compounds are unstable in solution because of polycondensation at pH > 10 and the formation of insoluble rhodium(iii) hydroxides at pH 5-10, their acidic derivatives with terminal aqua ligands acted as the objects of the study. Optimal separation conditions were achieved using sodium perchlorate as a background electrolyte, a voltage of +20 kV and pH 2.6. Rhodium(iii) species with different nuclearities were identified in accordance with their UV spectra and the regularities of electrophoretic migration in the capillary. The presence of a dimer was also verified by the spiking of the mixture under investigation with a previously synthesised complex [Rh 2 (μ-OH) 2 (H 2 O) 8 ](NO 3 ) 4 , which confirms the correct identification.

The hydrolysis of [RhCl 6 ] 3- in NaOH-water solutions was studied by spectrophotometric methods. The reaction proceeds via successive substitution of chloride with hydroxide to quantitatively form [Rh(OH) 6 ] 3- . Ligand substitution kinetics was studied in an aqueous 0.434-1.085 M NaOH matrix in the temperature range 5.5-15.3 °C. Transformation of [RhCl 6 ] 3- into [RhCl 5 (OH)] 3- was found to be the rate-determining step with activation parameters of ΔH † = 105 ± 4 kJ mol -1 and ΔS † = 59 ± 10 J K -1 mol -1 . The coordinated hydroxo ligand(s) induces rapid ligand substitution to form [Rh(OH) 6 ] 3- . By simulating ligand substitution as a dissociative mechanism, using density functional theory (DFT), we can now explain the relatively fast and slow kinetics of chloride substitution in basic and acidic matrices, respectively. Moreover, the DFT calculated activation energies corroborated experimental data that the kinetic stereochemical sequence of [RhCl 6 ] 3- hydrolysis in an acidic solution proceeds as [RhCl 6 ] 3- → [RhCl 5 (H 2 O)] 2- → cis-[RhCl 4 (H 2 O) 2 ] - . However, DFT calculations predict in a basic solution the trans route of substitution [RhCl 6 ] 3- → [RhCl 5 (OH)] 3- → trans-[RhCl 4 (OH) 2 ] 3- is kinetically favored.