相转移法制备PdMo催化剂及其氧还原活性

以四丁基氢氧化铵作为相转移剂,以硼氢化钠为还原剂,利用相转移法在二氯甲烷中制备了一系列不同比例的Pd_xMo/C(Pd/Mo的原子比x=1、2、3、4、5)催化剂。透射电镜(TEM)图像显示,Pd_x Mo/C是呈2～4 nm的圆形颗粒,尺寸均匀、分散性良好。X射线衍射(XRD)结果表明,加入第二组元Mo后,Pd的晶格发生扩张,调节了 Pd的几何结构。此外,X射线光电子能谱(XPS)结果表明,相对于Pd/C,Pd_4Mo/C的Pd3d_(5/)2结合能负移了 0.50 eV,说明电负性较大的Pd从Mo吸电子,电子结构发生改变。氧还原反应(ORR)结果表明,不同比例的Pd_xMo/C催化剂活性均优于Pd/C,其中当x=4时,ORR活性最佳,其起始电位和半波电位分别为0.876和0.813 V,高于商业Pt/C的0.870和0.810 V。此外,在经过3 h的运行之后电流密度仍保留82.9%,与商业Pt/C相比具有明显的优势。     

Thermodynamik und Struktur von Ni1−xTe*

Zusammenfassung DurchEMK-Messungen und Röntgenbeugungsaufnahmen wurden die thermodynamischen und strukturellen Eigenschaften von Ni₁–xTe untersucht. Die Phase Ni₁–xTe reicht von NiTe (x=0) mit dem Strukturtype des NiAs bis zu Ni_0,5Te mit dem Strukturtyp des CdJ₂. Das Phasenfeld zwischen den beiden Verbindungen ist homogen und zeigt umx=0,25 einen Übergang zweiter Ordnung. Bei dieser Zusammensetzung ändert sich der Anstieg der Kurve Ni-Aktivität gegen Zusammensetzung. Auch der Gitterparameterc ₀ ändert sich drastisch, und Beugungslinien der geordneten CdJ₂-Struktur beginnen aufzutreten. Die Intensität der Beugungslinien ändert sich von der NiAs-Struktur bis zur CdJ₂-Struktur gleichmäßig. Istx<0,2, so stimmen die Intensitäten mit denen überein, die man für die NiAs-Struktur berechnet, fürx>0,4 mit denen der CdJ₂-Struktur. Aus den Aktivitätsmessungen wurde die Fehlstellenwechselwirkungsenergie berechnet. In dem Strukturtyp NiAs ist die Wechselwirkungsenergie zwischen zwei Leerstellen gleich Null. Die Leerstellen stoßen einander also weder ab noch ziehen sie einander an, sie sind also statistisch verteilt. Im Bereich der CdJ₂-Struktur ist die Wechselwirkungsenergie zwischen zwei Leerstellen positiv, und zwarE ₁₁=26,5 kcal/Mol. Die Leerstellen stoßen einander ab, und dac ₀/2 kleiner ist alsa ₀, trachten die Leerstellen, benachbarte Schichten zu vermeiden, und bilden so die CdJ₂-Struktur.

---

Thermodynamics and Structure of Ni_1–xTe

The thermodynamic properties and structural properties of Ni_1–xTe have been studied using galvanic cell and X-ray diffraction techniques. The Ni_1–xTe phase extends from NiTe (x=0) which has a NiAs type structure to Ni_0.5Te (x=0.5) which has the CdI₂ structure. The phase field between the two compounds is continuous and a second order type transition is taking place aroundx=0.25. At that composition the Ni-activity vs. composition curve changes slope. Thec _o lattice parameter also changes drastically and diffraction lines due to the ordered CdI₂ structure start to appear. The intensity of diffraction lines varies smoothly from the NiAs structure to the CdI₂ structure. The intensities agree with that calculated for NiAs whenx<0.2, it agrees with the CdI₂ intensity whenx>0.4. From the activity measurement, the defect interaction energy was calculated. In the NiAs type structure, the vacancyvacancy interaction energy is zero, the vacancies do not repel or attract each other and thus are random. In the CdI₂ structure region the vacancy-vacancy interaction energy is positiveE ₁₁=26.5 kcal/mole. The vacancies repel each other and asc ₀/2 is smaller thana ₀ the vacancies tend to avoid adjacent layers and thus form the CdI₂ structure.

---

---

Mit 9 Abbildungen

---

Herrn Prof. Dr.H. Nowotny gewidmet.

---

Diese Arbeit wurde zum Teil durch die National Aeronautics and Space Administration mit dem Grant NSG (T) 43 1101-020 unterstützt.     

NO Reduction Over Noble Metal Ionic Catalysts

In last 40 years, catalysis for NO _x removal from exhaust gas has received much attention to achieve pollution free environment. CeO₂ has been found to play a major role in the area of exhaust catalysis due to its unique redox properties. In last several years, we have been exploring an entirely new approach of dispersing noble metal ions in CeO₂ and TiO₂ for redox catalysis. We have extensively studied Ce_1−x M _x O_2−δ (M = Pd, Pt, Rh), Ce_1−x−y A _x M _y O_2−δ (A = Ti, Zr, Sn, Fe; M = Pd, Pt) and Ti_1−x M _x O_2−δ (M = Pd, Pt, Rh, Ru) catalysts for exhaust catalysis especially NO reduction and CO oxidation, structure–property relation and mechanism of catalytic reactions. In these catalysts, lower valent noble metal ion substitution in CeO₂ and TiO₂ creates noble metal ionic sites and oxide ion vacancy. NO gets molecularly adsorbed on noble metal ion site and dissociatively adsorbed on oxide ion vacancy site. Dissociative chemisorption of NO on oxide ion vacancy leads to preferential conversion of NO to N₂ instead of N₂O over these catalysts. It has been demonstrated that these new generation noble metal ionic catalysts (NMIC) are much more catalytically active than conventional nano crystalline noble metal catalysts especially for NO reduction.     

Interactions in the subsolidus region of the Na2MoO4-NiMoO4-Fe2(MoO4)3 system

Phase relations have been investigated in the subsolidus region of the Na₂MoO₄-NiMoO₄-Fe₂(MoO₄)₃ system by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. The phase of variable composition Na_1−x Ni_1−x Fe_1+x (MoO₄)₃(0≤x≤0.5) with the NASICON structure (space group R c) and the NaNi₃Fe(MoO₄)₅ ternary molybdate crystallizing in the triclinic crystal system (space group P ) have been obtained. A high conductivity was found in Na_1−x Ni_1−x Fe_1+x (MoO₄)₃, which allows one to consider this phase of variable composition as a promising solid electrolyte with sodium ion conduction. Original Russian Text ? N.M. Kozhevnikova, A.V. Imekhenova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 695–700.     

Palladium(<Emphasis Type="SmallCaps">I</Emphasis>) and palladium(0) carbonyl bromide complexes

New Pd^I and Pd⁰ carbonyl bromide complexes co-existing in the same crystal were synthesized and studied by X-ray diffraction analysis. The crystals consist of dimeric complex anions composed of the central Pd(μ-CO)₂Pd fragment and four partially disordered terminal ligands (CO and Br⁻). The complexes were characterized by IR, ESR, and X-ray photoelectron spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1349–1355, June, 2005.     

Structural features of the formation of La1?xCaxFeO3?δ (0 ≤x ≤ 0.7) hetero valent solid solutions

A synthesis method with the use of polymer-salt compositions (calcination temperature 800°C) provides the preparation of various solid solutions of a La_1−x Ca _x FeO_3−δ series in the 0≤ x≤ 0.7 range, which belong to the perovskite structure type. A morphotropic phase transition occurs from the orthorhombic perovskite modification (0≤ x ≤ 0.4) to the cubic one (0.5 ≤ x≤ 0.7). A growing number of microdistortions in the perovskite structure and the formation of a microblock structure in the morphotropic phase transition region are observed with increasing degree of calcium substitution for lanthanum. Calcination of solid solutions with x = 0.6 and 0.7 at temperatures above 1000°C in the air or under conditions of reduced oxygen partial pressure (laboratory vacuum of 10⁻³ Torr) results in the formation of a nanostructured state with coherently grown blocks of perovskite and Grenier phase, which is due to irreversible oxygen loss.     

Electronic Modulation of Palladium in Metal Phosphide Nanoparticles for Chemoselective Reduction of Halogenated Nitrobenzenes

Tuning the electronic property of a transition metal plays an important role in the selective catalysis. Herein, the control synthesis of (Pd_xNi_y)‐P nanoparticles is reported. The binding energy of Pd3d_5/2 as a function of x/y ratio is well tunable from 335.3 to 335.9 eV. The composition‐induced electronic modulation was correlated with the selective catalysis of (Pd_xNi_y)‐P in the reduction of halogenated nitrobenzenes. The electro‐deficiency of Pd helped to improve the selectivity. The amorphous (Pd₃₈Ni₂₆)P₃₆/C performed an exceptional selectivity in comparison with other related (Pd‐Ni)‐P/C, Pd₃₈Ni₂₆/C, and Pd/C. Various halogenated nitrobenzenes (chlorides, bromides, and iodide) were tolerant and the corresponding halogenated anilines were obtained in high yields. This work provides some clues for the rational design of bimetallic phosphides with covalent interactions to boost the catalysis.     

Glycine-assisted hydrothermal synthesis of nanostructured Co x Ni1−x –Al layered triple hydroxides as electrode materials for high-performance supercapacitors

Nanostructured Co _x Ni_1−x –Al layered triple hydroxides (Co _x Ni_1−x –Al LTHs) have been successfully synthesized by a facile hydrothermal method using glycine as chelating agent. The samples were characterized by X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy and scanning electron microscopy. The morphologies of Co _x Ni_1−x –Al LTHs varied with the Co content and its effect on the electrochemical behavior was studied by cyclic voltammetry and galvanostatic charge–discharge techniques. Electrochemical data demonstrated that the Co _x Ni_1−x –Al LTHs with Co/Ni molar ratio of 3:2 owned the best performance and delivered a maximum specific capacitance of 1,375 F g⁻¹ at a current density of 0.5 A g⁻¹ and a good high-rate capability. The capacitance retained 93.3% of the initial value after 1,000 continuous charge–discharge cycles at a current density of 2 A g⁻¹.     

Calorimetric search for the discontinuity in Fe<Subscript>0.96</Subscript>S-Ni<Subscript>0.96</Subscript>S solid solutions

Heat capacity of unstable quenched solid solutions (Fe_1−xNi_x)_0.96S was measured by DSC (enthalpy method and scanning heating). According to optic microscopy and X-ray powder diffraction, the samples are homogeneous phase of NiAs type with unit cell parameters changing regularly with composition. Heat capacity changes with composition irregularly due to the difference in magnetic properties of the end members: C _p/1.96R=4.1 for Fe-rich samples and 3.3 for Ni-rich ones. There is no exact limit between two types of magnetic ordering. Instead, samples with intermediate composition (0.7<x<0.8) show large fluctuations in C _p due to the inconsistency of alternative (FeS and NiS) types of magnetic ordering.     

Thermodynamic properties of Eu-Pd melts

Partial and integral enthalpies of mixing of melts of the Eu-Pd system were determined by calorimetry at 1300 K in the concentration interval of 0 < x _Pd < 0.37. It was established that the first partial enthalpy of mixing of Pd was −158 ± 2 kJ/mol. The thermodynamic properties of Eu-Pd melts were simulated according to the theory of ideal associated solutions over a wide interval of concentrations and temperatures. It was shown that the activities of components display strong negative deviations from Raoult’s law, and the minima of the integral Gibbs energies and enthalpies of mixing were found at x _Pd = 0.65.     

Electrophysical properties of materials based on BaGdCo2O5 + δ

The phase composition, linear thermal expansion coefficient, electroconductivity (in the temperature interval 600–900°C and partial pressures of oxygen 10⁻⁵–0.21 atm) of solid-oxide materials based on gadolinium-barium cobaltite doped with 3d-elements BaGdCo_{2 − x} Me _x O_{5 + δ}, Me = Cu, Fe; x = 0.0, 0.2, …, 2.0 were investigated. The homogeneity regions of samples were established by means of X-ray phase analysis. It was shown that the linear thermal expansion coefficient of cobaltite decreases with an increase in the copper or iron concentration. It was established that the electroconductivity of BaGdCo_{2 − x} Me _x O_{5 + δ} decreases with an increase in x. We concluded that upon a decrease in p(O₂), the electroconductivity of samples first decreases and then reaches a horizontal plateau.     

Synthesis, characterization, and electrical conductivity of new Aurivillius-type oxide-ion conductor

A new oxide-ion conductor of Aurivillius family with a general formula Bi₂Al _x V_{1 − x} O_{5.5 − x − δ}; 0 ≤ x ≤ 0.20 (BIALVOX) was synthesized by the sol-gel citrate route. Powder X-ray diffraction and simultaneous thermogravimetric and differential thermal analyses confirmed that the calcination of BIALVOX xerogels is fully completed at around 500°C after three hours of thermal treatment. It has been found that the β-orthorhombic phase is stabilized with compositions x ≤ 0.07, whereas the stabilization of the γ′-phase takes place for x ≥ 0.10. AC impedance spectroscopic investigation suggested that the charge accumulation at grain boundaries is thermally activated process. However, the maximum electrical conductivity (7.73 × 10⁻⁵ S cm⁻¹) noticed for BIALVOX.13 at 300°C was attributed to the maximum vacancy concentration in the equatorial planes, responsible for the ion diffusion through the structure. This has been further evidenced by the temperature dependence of dielectric permittivity.     

Phase relationships and some magnetic properties of spinels in the systems M1−xNixCr2S4 where M = Mn,Fe, Co

Phase relationships between spinel and defect NiAs structures in the systems M_1?xNi_xCr₂S₄ (where M = Mn, Fe, Co) were investigated. It was found that the spinel structure is stable between x = 0 and x = 0.3 when M = Mn or Fe. When M = Co the spinel is formed in the region x = 0 to x ～ 0.4. The apparent stabilization of the defect NiAs phase by Ni²⁺ may be related to the strong sixfold site preference of Ni²⁺. Curie temperatures of all three ferrimagnetic systems increases with increasing Ni²⁺ substitution. This is probably due to higher NiS covalency.     

Synthesis and characterization of mesoporous Mn–Ni oxides for supercapacitors

Mesoporous Mn–Ni oxides with the chemical compositions of Mn_1-x Ni _x O _δ (x = 0, 0.2, and 0.4) were prepared by a solid-state reaction route, using manganese sulfate, nickel chloride, and potassium hydroxide as starting materials. The obtained Mn–Ni oxides, mainly consisting of the phases of α- and γ-MnO₂, presented irregular mesoporous agglomerates built from ultra-fine particles. Specific surface area of Mn_1–x Ni _x O _δ was 42.8, 59.6, and 84.5 m² g⁻¹ for x = 0, 0.2, and 0.4, respectively. Electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge/discharge in 6 mol L⁻¹ KOH electrolyte. Specific capacitances of Mn_1-x Ni _x O _δ were 343, 528, and 411 F g⁻¹ at a scan rate of 2 mV s⁻¹ for x = 0, 0.2, and 0.4, respectively, and decreased to 157, 183, and 130 F g⁻¹ with increasing scan rate to 100 mV s⁻¹, respectively. After 500 cycles at a current density of 1.24 A g⁻¹, the symmetrical Mn_1–x Ni _x O _δ capacitors delivered specific capacitances of 160, 250, and 132 F g⁻¹ for x = 0, 0.2, and 0.4, respectively, retaining about 82%, 89%, and 75% of their respective initial capacitances. The Mn_0.8Ni_0.2O _δ material showed better supercapacitive performance, which was promising for supercapacitor applications.     

Synthesis and magnetic properties of nanocomposite Ni1?xCoxFe2O4–BaTiO3 fibers by organic gel-thermal decomposition process

Nanocomposites of ferrite and ferroelectric phases are attractive functional ceramic materials. In this work, the nanocomposite Ni_1−x Co _x Fe₂O₄–BaTiO₃(x = 0.2, 0.3, 0.4, 0.5) fibers with fine diameters of 3 ~ 7 μm and high aspect ratios were synthesized by the organic gel-thermal decomposition process from the raw materials of citric acid and metal salts. The structure, thermal decomposition process and morphologies of the gel precursors and the resultant fibers derived from thermal decomposition of the gel precursors were characterized by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction and scanning electron microscopy. The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer. The nanocomposite fibers of ferrite Ni_1−x Co _x Fe₂O₄ and perovskite BaTiO₃ are formed at the calcination temperature of 900 °C for 2 h. The average grain sizes of Ni_1−x Co _x Fe₂O₄ and BaTiO₃ in the nanocomposite fibers increase from about 15 nm to approximately 67 nm with the increasing calcination temperatures from 900 to 1,180 °C. The saturation magnetization of the nanocomposite Ni_1−x Co _x Fe₂O₄–BaTiO₃(x = 0.2, 0.3, 0.4, 0.5) fibers increases with the increase of grain sizes of Ni_1−x Co _x Fe₂O₄ and Co content, while the coercivity reaches a maximum value at the single-domain size of about 65 nm of Ni_0.5Co_0.5Fe₂O₄ obtained at the calcination temperature of 1,100 °C.     

CuO/Ce<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> catalysts: synthesis,characterization, and catalytic performance for low-temperature CO oxidation

Ce _x Sn_1−x O₂ metal oxides were prepared by a citrate method and used as supports for CuO/Ce _x Sn_1−x O₂ catalysts. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy, high-resolution TEM, and temperature-programmed reduction techniques. XRD analysis indicated that the Ce _x Sn_1−x O₂ samples maintain the fluorite structure and form a solid solution when x = 0.9 or 0.8. TPR analysis revealed that two kinds of copper species are present on the surface of the Ce _x Sn_1−x O₂ support. The catalytic properties of the CuO/Ce _x Sn_1−x O₂ catalysts were evaluated for low-temperature CO oxidation using a microreactor-GC system. The effects of Ce/Sn ratio and CuO loading on the catalytic performance were investigated. The results showed that these CuO/Ce _x Sn_1−x O₂ catalysts are very active for low-temperature CO oxidation. The 650 °C calcined 7 wt%-CuO/Ce _x Sn_1−x O₂ catalyst exhibited the highest catalytic activity.     

High Performance Pd,PdNi, PdSn and PdSnNi Nanocatalysts Supported on Carbon Nanotubes for Electrooxidation of C2C4 Alcohols

Nanocatalysts Pd, Pd₈Ni₂, Pd₈Sn₂ and Pd₈Sn₁Ni₁ supported on multi‐walled carbon nanotubes (MWCNTs) were successively synthesized by the chemical reduction method in the glycol‐water mixture solvent. Transmission electron microscopy results show that the prepared Pd, Pd₈Ni₂, Pd₈Sn₂ and Pd₈Sn₁Ni₁ nanoparticles are uniformly dispersed on the surface of MWCNTs. The average particle sizes of the nanocatalysts are 3.5–3.8 nm. Electroactivity of the prepared catalysts towards oxidation of ethanol, 1‐propanol, 2‐propanol, n‐butanol, iso‐butanol and sec‐butanol (C2? C4 alcohols) in alkaline medium was studied by cyclic voltammetry and chronoamperometry. The current density obtained for the electrooxidation of C2? C4 alcohols depends on the catalysts and the various structures of the alcohols. Addition of Sn or/and Ni to Pd nanoparticles enhances the electroactivity of the Pd/MWCNT catalyst. Furthermore, the ternary Pd₈Sn₁Ni₁/MWCNT catalyst presents the highest electroactivity for the oxidation of C2? C4 alcohols among the prepared catalysts. Electrocatalytic activity order among propanol isomers and butanol isomers is as follows respectively: 1‐propanol > 2‐propanol, and n‐butanol > iso‐butanol > sec‐butanol > tert‐butanol. This is consistent with the Mulliken charge value of the carbon atom bonded with hydroxyl group in the corresponding alcohol molecule.     

Phase equilibria in the palladium-rich part of the Pd–Au–Cu–Sn quaternary system

The solubility of tin in the phases of Pd–Au–Sn and Pd–Cu–Sn ternary systems and a Pd–Au–Cu–Sn quaternary system with a fixed Pd: Au: Cu ratio of 11.1: 1: 4.6 is studied via microstructural, X-ray diffraction, and energy dispersive analysis. It is found that a quaternary alloy in equilibrium with a solid solution based on Pd, Au, and Sn contains a τ₁ compound with structure which is derivative of the In type. It contains ~15 at % Sn and is a solid solution of the same compounds identified earlier in Pd–Au–Sn and Pd–Cu–Sn ternary systems. In addition, a quaternary alloy with a content of 20 at % Sn also contains a τ₂ compound with the Pd₂CuSn own type and can barely dissolve gold. The obtained data are used to construct a three-dimensional model of the Pd-rich part of the isothermal tetrahedron of the Pd–Au–Cu–Sn system and diagrams of the tin solubility isolines in palladium-rich alloys of the quaternary system at 500°С.     

Structural and low temperature Raman scattering studies in SrTi<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3</Subscript> nanoparticles synthesized by sol–gel method

We investigate effects of Co dopant concentration on the structure and low temperature Raman scattering properties in SrTi_1−x Co _x O₃ (x = 0.00, 0.10, 0.20, 0.30) nanoparticles prepared by sol–gel method. The dopant induced changes are studied by XRD, and Raman scattering measurements. The results show an average particle size of about 20 nm depending on the Co content and the lattice parameters decrease as increasing the Co content. In the Raman spectra, a broad structure in the region 100–500 cm⁻¹ is almost absent and the peaks in the region 600–800 cm⁻¹ show different weights with respect to SrTiO₃, relating to structural changes. The anomalous change in the area ratio of Raman peaks as function of temperature suggests a phase transition in our samples in the range of 110–130 K. These results indicate that the Co ion has replaced the site of Ti in unit cell. This novel route also demonstrates the advantage of synthesizing the compound with low annealing temperature.     

Synthesis and properties of PdSn/Al2O3 and PdSn/SiO2 prepared by solvated metal atom dispersed method

A series of solvated metal atom dispersion (SMAD) catalysts: Pd/SiO₂, Pd/Al₂O₃, Sn/SiO₂, Sn/Al₂O₃, Pd_xSn_y/SiO₂ and Pd_xSn_y/Al₂O₃. It was prepared by simultaneous evaporation of Pd and Sn. The metals were co-deposited at 77 K using acetone, 2-propanol and THF to produce colloids “in situ” all the supported catalyst were characterized by chemisorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and TPR. This series of catalyst were tested for crotonaldehyde hydrogenation in gas phase to obtain crotyl alcohol.