Surface redox polymerized SPEEK–MO2–PANI (M = Si, Zr and Ti) composite polyelectrolyte membranes impervious to methanol

We reported sulfonated poly(ether ether ketone) (SPEEK, 61% degree of sulfonation)–metal oxides (MO₂:SiO₂, TiO₂ and ZrO₂)–polyaniline composite membranes. Metal oxides were incorporated into the swelled SPEEK membrane by sol–gel method and cured by thermal treatment. SPEEK–metal oxide membranes surfaces were modified with polyaniline (PANI) by a redox polymerization process. It was observed that water retention capacity of membrane was increased and methanol permeability was reduced due to synergetic effect of metal oxides and surface modification with polyaniline. These composite membranes showed extremely low methanol permeability (1.9–1.3 × 10⁻⁷ cm² s⁻¹), which was lower than till reported values either for SPEEK–metal oxide or SPEEK/PANI membranes. Relatively high selectivity parameter (SP) values at 343 K of these membranes, especially S–SiO₂–PANI and S–TiO₂–PANI, indicated their great advantages over Nafion117 (N117) membrane for targeting on moderate temperature applications due to the synergetic effect of MO₂ and PANI in SPEEK matrix. S–TiO₂–PANI and N117 showed comparable cell performance in direct methanol fuel cell (DMFC).     

Comparative study of CO2 hydrogenation to methanol on cubic bixbyite-type and rhombohedral corundum-type indium oxide

Hydrogenation of CO₂ to value-added chemicals has attracted much attention all through the world. In₂O₃ with cubic bixbyite-type (denoted as c-In₂O₃) is well known for its high CO₂ hydrogenation activity and CH₃OH selectivity at high temperature. However, the other structure of In₂O₃ with rhombohedral corundum-type (denoted as rh-In₂O₃) rarely been investigated as catalyst. Herein, c-In₂O₃ and rh-In₂O₃ were prepared and comparatively studied for CO₂ hydrogenation. The results indicated that c-In₂O₃ showed higher CO₂ conversion activity than rh-In₂O₃ due to the impressive reducibility and reactivity. Whereas rh-In₂O₃ had higher CH₃OH selectivity due to weaker CH₃OH and stronger CO adsorption on rh-In₂O₃. Although c-In₂O₃ and rh-In₂O₃ catalysts showed different CO₂ hydrogenation performance, in-situ diffuse reflectance infrared Fourier transform spectroscopy showed CO₂ can be reduced to CO through redox cycling and hydrogenation to CH₃OH through formate path.     

Nanostructured spinel-type M(M = Mg,Co, Zn)Cr2O4 oxides: novel adsorbents for aqueous Congo red removal

Nanostructured spinel-type M(M = Mg, Co, Zn)Cr₂O₄ oxides with novel adsorbents for aqueous Congo red removal were synthesized by a polyacrylamide gel method and studied for their phase structure, microstructure, adsorption performance, and multiferroic behavior. The phase structure and purity analysis revealed that the nanostructured spinel-type M(M = Mg, Co, Zn)Cr₂O₄ oxides presented a spinel-type cubic structure, and the formation of a secondary phase such as Cr₂O₃, MgO, ZnO, or Co₃O₄ was not observed. The microstructure characterization confirmed that the spinel-type MCr₂O₄ oxides grew from fine spherical particles to large rhomboid particles. Adsorption experiments of spinel-type MCr₂O₄ oxides for adsorption of Congo red dye were fitted well with the pseudo-second-order kinetics. The adsorption capacity of the ZnCr₂O₄ oxide (44.038 mg/g, pH 7, temperature 28 °C, initial dye concentration 30 mg/L) was found to be higher than that of MgCr₂O₄ oxide (43.592 mg/g, pH 7, temperature 28 °C) and CoCr₂O₄ oxide (28.718 mg/g, pH 7, temperature 28 °C). The effects of initial adsorbent concentration, initial dye concentration, pH, and temperature between the ZnCr₂O₄ oxide and Congo red dye at which optimal removal occurs, were performed. The thermodynamic studies confirmed that a high temperature favors the adsorption of Congo red dye onto ZnCr₂O₄ oxide studied. The nanostructured spinel-type M(M = Mg, Co, Zn)Cr₂O₄ oxides that exhibited high adsorption performance for adsorption of Congo red dye can be ascribed to the synergistic effect of electrostatic interaction, pore filling, and ion exchange. The present work suggested that the nanostructured spinel-type M(M = Mg, Co, Zn)Cr₂O₄ oxides have excellent adsorption performance and multiferroic behavior, which shows potential applications for removal of the Congo red dye from wastewater, magnetic memory recording media, magnetic sensor, energy collection and conversion device, and read/write memory.     

NaBH4处理LaCuZnX(X=Zr、Al、Zr+Al)(类)钙钛矿型催化剂及其CO2加氢合成甲醇性能的研究

采用共沉淀法分别制备了不同F-T组分(Fe、Co、Ni)改性的KCuZrO_2催化剂,并用于催化CO加氢合成异丁醇。通过BET、XRD、TEM、XPS、H_2-TPR、CO-TPD以及in-situ DRIFTS对催化剂进行了表征。结果显示,F-T组分的加入促进了乙醇和丙醇的形成,但是对异丁醇选择性影响不同。结果表明,Fe促进了催化剂中各组分的分散,活性组分Cu在催化剂表面发生了富集,提高了H_2/CO活化吸附;另外,KFeCuZrO_2的催化剂表面含有较多的C_1物种,有利于乙醇和丙醇进一步发生β-加成反应得到异丁醇,而Co和Ni改性的催化剂上缺少足够的C_1物种,因此,异丁醇的选择性并未明显增加。Co的引入对催化剂结构以及Cu的分散影响不大,但是Co改性后催化剂性能有所下降,其原因是催化剂发生了失活;Ni添加后催化剂比表面积有所减小,且催化剂表面Cu/Zr物质的量比也降低到0.19,催化剂粒径增大,Cu-Zr之间相互作用减弱,异丁醇选择性降低。     

Synthesis,structure, and optical properties of a series of quaternary oxides,K2Ba(MO4)2 (M = Cr,Mo, W)

Single crystals of a family of quaternary oxides K₂Ba(MO₄)₂ (M = Cr, Mo, W) have been grown for the first time. The crystals were grown in a hydroxide-based hydroflux. The compounds crystallize in space group R $\overline{3}$m and, according to single-crystal X-ray diffraction structure determination, are isostructural with the mineral Palmierite. All compounds show anti-site mixing of the potassium and barium. The degree of mixing appears to be determined indirectly by the M-O bond distance. Diffuse reflectance spectra and room-temperature luminescence were measured for each compound.     

Binding energies and bonding nature of MX(CO)(PH3)2(C60) (M = Rh or Ir; X = H or Cl): Theoretical study

IrH(CO)(PH₃)₂(C₆₀), IrCl(CO)(PH₃)₂(C₆₀), and RhH(CO)(PH₃)₂(C₆₀) were theoretically investigated with DFT and MP2 to MP4(SDQ) methods.  Because the DFT method considerably underestimates the binding energy compared to the MP2 method, their binding energies were evaluated by the ONIOM(MP4(SDQ):UFF) method.  The binding energy decreases in the order IrH(CO)(PH₃)₂(C₆₀) (59.4) > RhH(CO)(PH₃)₂(C₆₀) (48.2) > Pt(PH₃)₂(C₆₀) (47.2) > IrCl(CO)(PH₃)₂(C₆₀) (43.0), where in parentheses are the binding energy (in kcal/mol) calculated with the ONIOM(MP4(SDQ):UFF) method and that of Pt(PH₃)₂(C₆₀) was calculated with the same method and the same basis sets in our previous work.  This decreasing order is interpreted in terms of the d_π orbital energy, the d orbital expansion, the presence of the empty d_σ orbital, and the distortion energy of the metal fragment induced by the complexation; for instance, the d_π orbital is at higher energy and more expands in IrH(CO)(PH₃)₂ than in the Rh analogue, which leads to the larger binding energy of IrH(CO)(PH₃)₂(C₆₀) than that of the Rh analogue. IrCl(CO)(PH₃)₂ is less favorable than IrH(CO)(PH₃)₂ because of the lower energy of d_π orbital.  Although the π-back donation is stronger in IrCl(CO)(PH₃)₂(C₆₀) than in RhH(CO)(PH₃)₂(C₆₀), the binding energy of IrCl(CO)(PH₃)₂(C₆₀) is smaller than that of RhH(CO)(PH₃)₂(C₆₀) due to the larger distortion energy of the IrCl-(CO)(PH₃)₂ moiety.  Although the d_π orbital of Pt(PH₃)₂ is at higher energy than that of IrH-(CO)(PH₃)₂, the binding energy of IrH(CO)(PH₃)₂(C₆₀) is larger than that of Pt(PH₃)₂(C₆₀) because the distortion energy is large and the d_σ orbital is doubly occupied in Pt(PH₃)₂(C₆₀).  It is also noted that these binding energies are much larger than those of the ethylene analogues like those of the Pt(0) complexes, which is reasonably interpreted in terms that the LUMO of C₆₀ is at much lower energy than those of ethylene.     

Mild hydrothermal synthesis,isomorphous substitution,crystal structure characterization and magnetic properties of BaMP2O7 (M = Mn,Cu)

At mild hydrothermal conditions triclinic modifications of BaMP₂O₇ (M = Mn and/or Cu) have been succeeded. The method offers cheap, one step, impurity free and chemical flexible fabrication of family of metal phosphates that are potential low-dimensional quantum magnets. Partial isomorphous substitution of the Mn²⁺ by Cu²⁺ resulted into mixed-metal solid that has been structurally and magnetically characterized. Rietveld refinement study confirmed the structures and revealed the influence of transition metal substitution. The temperature-dependent magnetic measurements revealed that the system is paramagnetic in almost all temperature range and an apparent antiferromagnetic phase transition occurs around 5 K. Using the Curie–Weiss law, a Curie–Weiss temperature, θ_P = −11.0 K, and a Curie constant C = 3.39 emu K mol⁻¹ was obtained. The small negative θ_P value and the χT behavior as a function of temperature reveal a weak antiferromagnetic interaction between the Cu²⁺/Mn²⁺magnetic centers.     

Synthesis and characterisation of the anion-ordered tellurides MGeTe (M = Co,Rh)

The synthesis and structural characterisation, carried out using a combination of single-crystal and powder X-ray diffraction, of the materials MGeTe (M = Co, Rh) are described. These phases adopt an ordered α-NiAs₂ structure, which can be considered intermediate between those of pyrite and marcasite. Electrical resistivity and Seebeck coefficient measurements, carried out over the temperature range 77 ≤ T/K ≤ 325, indicate that these materials are n-type semiconductors.     

Marked variations of proton release energy of the G–M (M = Li, Na) in the water circumstance

The variations of N1–H proton release energy of G–M (M = Li, Na) cation have been investigated employing density functional theory using B3LYP/6-31++G^**//B3LYP/6-31+G^* method. There are three modes (NO mode, N mode and O mode) when the hydrated-M⁺ bonds to guanine. The bonding energy of the hydrated M⁺ to the guanine reduces following the increase in the number of water molecules. The proton release energies of the G–M⁺ complexes are calculated at the condition of the different numbers of water molecules and the different modes of water molecules bonded on the G–M⁺. The results show that the difference of proton release energy on three modes is very small, and the proton release energies of the Na⁺ complexes are slightly larger than those of the Li⁺ complexes. The effect on the N1–H proton release is very small when the water molecules bond on the M⁺ cation, but the effect is very large when the water molecule bonds on the N1–H proton and the proton releases as the hydrated proton. The IR vibrational frequencies of the hydrated G–M⁺ complexes are calculated using analytic second derivative methods at the B3LYP/6-31+G^* level. The vibrational frequency analyses show that the changes of the vibrational frequency are consistent with the changes of geometry and the changes of the N1–H proton release energy. The N1–H proton release (N1–H proton release energy: 45–60 kcal/mol) of the guanine occurs easily under the biological environment.     

Haptotropic migration of M(CO)3 (M = Cr, Mo, W) on substituted phenanthrene

The haptotropic migration of Cr(CO)₃, Mo(CO)₃ and W(CO)₃ moieties on a substituted phenanthrene has been studied theoretically using gradient-corrected density functional theory. The stationary points (minima and transition states) on the energy hypersurface characterizing the migrating process of the metal fragment over the aromatic system have been located. Furthermore, the energetic and structural differences between complexes of the three metals Cr, Mo and W and the effect of a high substitution of one arene ring on the reaction energy profile have been analyzed. The possibility to design a molecular switch based on the substituent pair R = O⁻/OH is investigated. It is concluded that the Mo and W complexes undergo a haptotropic migration more easily than the corresponding Cr system.     

Polyol-mediated low-temperature synthesis of crystalline tungstate nanoparticles MWO4 (M = Mn,Fe, Co,Ni, Cu,Zn)

A polyol-mediated synthesis is presented as a general access to nanoscaled transition-metal tungstates MWO₄ (M = Mn, Fe, Co, Ni, Cu, Zn). Using simple inorganic salts as starting materials, uniform and readily crystalline nanoparticles are prepared under mild conditions (T < 220 °C). The nanoparticles are of high quality in terms of small diameter (<20 nm), high surface area (up to 200 m² g⁻¹), phase purity and yield (>85%). Size, morphology and composition can be adjusted by precise variation of the reaction parameters, including type of starting material, duration and temperature of reaction. The transition-metal tungstate nanoparticles are fully functional, exhibiting typical properties of this class of materials, for instance, superparamagnetism (CoWO₄), luminescence (ZnWO₄) and photocatalytic activity (CuWO₄).     

Influence of Ce substitution in LaMO3 (M = Co/Ni) perovskites for COx-free hydrogen production from ammonia decomposition

The La based perovskite type LaMO₃ (M = Ni, Co) oxides were prepared by combustion synthesis method using citric acid as organic fuel. These catalyst precursors tested for ammonia decomposition. The LaNiO₃ and LaCoO₃ catalysts showed good activity for NH₃ decomposition. The LaNiO₃ catalyst displayed greater activity than LaCoO₃. This due to high surface area and easily reducibility of Ni species. A 50% of La was substituted by Ce in both LaNiO₃ and LaCoO₃ catalysts. A remarkable effect on catalytic performance was observed with the partial substitution of La by Ce in perovskite catalyst especially at lower temperatures. The La_0.5Ce_0.5NiO₃ catalyst exhibited highest activity among all prepared samples. The achieved superior activity is due to boost in surface area, reducibility and suitable basicity. The SEM elemental mapping of La_0.5Ce_0.5NiO₃ catalyst concluded that metal oxide constituents dispersed homogeneously. The La_0.5Ce_0.5NiO₃ catalyst showed excellent stable catalytic performance during 50 h time on study at 550 °C.     

Photocatalytic properties of CoOx-loaded nano-crystalline perovskite oxynitrides ABO2N (A = Ca,Sr, Ba,La; B = Nb,Ta)

Highly crystalline niobium- and tantalum-based oxynitride perovskite nanoparticles were obtained from hydrothermally synthesized oxide precursors by thermal ammonolysis at different temperatures. The samples were studied with respect to their morphological, optical and thermal properties as well as their photocatalytic activity in the decomposition of methyl orange. Phase pure oxynitrides were obtained at rather low ammonolysis temperatures between 740 °C (CaNbO₂N) and 1000 °C (BaTaO₂N). Particle sizes were found to be in the range 27 nm–146 nm and large specific surface areas up to 37 m² g⁻¹ were observed. High photocatalytic activities were found for CaNbO₂N and SrNbO₂N prepared at low ammonolysis temperatures. CoO_x as co-catalyst was loaded on the oxynitride particles resulting in a strong increase of the photocatalytic activities up to 30% methyl orange degradation within 3 h for SrNbO₂N:CoO_x.     

Combustion synthesis and luminescent properties of metal yttrium borates M3Y2 (BO3)4:Eu3+ (M = Ba,Sr) for PDPs applications

The polycrystalline powder samples of Eu³⁺ activated; mixed metal yttrium borate phosphors M₃Y₂(BO₃)₄ (M = Ba, Sr) with improved color purity of red emission for plasma display panels (PDPs) were prepared by solution combustion technique. The synthesis is based up on the exothermic reaction between the fuel (Urea) and oxidizer (Ammonium nitrate) .The heat generated in the reaction is utilized for auto combustion of ingredients. The formation of desired product and crystal structure was confirmed by powder XRD technique; while particle morphology was studied using FE-SEM. Samples under 254 and 147 nm excitation showed intense and pure red emission around 613 nm corresponding to the electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺, CIE chromaticity coordinates of synthesized phosphors was found to be (x = 0.67, y = 0.32) close to National Television Standard Committee (NTSC) for red color; found suitable to employ in plasma display panels (PDPs) applications.     

Water-soluble complexes MX2L2 (M = Pd,Pt; L = PPh2(C6H4-p-SO3K)): Synthesis,stereoisomerism, and catalytic activities for aromatic cyanation in n-heptane/water biphasic solution

Reaction of (COD)MX₂ (M = Pd, Pt; X = Cl, I; COD = 1,5-cyclooctadiene) and P(C₆H₅)₂(C₆H₄-p-SO₃K) afforded water-soluble complexes MX₂{P(C₆H₅)₂(C₆H₄-p-SO₃K)}₂ (M = Pd; X = Cl (1), M = Pt; X = Cl (2), I (3)) in high yields. Complexes 1–3 were fully characterized by various spectroscopic methods (IR, ¹H-, ¹³C{¹H}- and ³¹P{¹H}-NMR spectroscopy) and elemental analyses. For 1 and 3, a mixture of the cis- and trans-isomer was produced from the reaction. For 2, however, only the cis-isomer was obtained. The stereochemistry of 1–3 can be assigned by the chemical shifts and the ¹J(Pt–P) values in ³¹P{¹H}-NMR spectral data. The ratios of the cis/trans isomers of 1 and 3 obtained from reactions in a range of solvents with various dielectric constants resulted in a little variation. However, addition of aqueous potassium halide solution to a DMSO-d₆ solution of 1 and 3 considerably increased the ratio of the cis/trans, respectively, indicating a strong intramolecular interligand Coulombic repulsion between the ionic phosphine ligands is present. Catalytic cyanation of aromatic iodide with KCN/ZnCl₂ in n-heptane/water biphasic system has been tested in the presence of 1–3 with base.     

Water-soluble complexes MX2L2 (M = Pd,Pt; L = PPh2(C6H4-p-SO3K)): Synthesis,stereoisomerism, and catalytic activities for aromatic cyanation in n-heptane/water biphasic solution

Reaction of (COD)MX₂ (M = Pd, Pt; X = Cl, I; COD = 1,5-cyclooctadiene) and P(C₆H₅)₂(C₆H₄-p-SO₃K) afforded water-soluble complexes MX₂{P(C₆H₅)₂(C₆H₄-p-SO₃K)}₂ (M = Pd; X = Cl (1), M = Pt; X = Cl (2), I (3)) in high yields. Complexes 1–3 were fully characterized by various spectroscopic methods (IR, ¹H-, ¹³C{¹H}- and ³¹P{¹H}-NMR spectroscopy) and elemental analyses. For 1 and 3, a mixture of the cis- and trans-isomer was produced from the reaction. For 2, however, only the cis-isomer was obtained. The stereochemistry of 1–3 can be assigned by the chemical shifts and the ¹J(Pt–P) values in ³¹P{¹H}-NMR spectral data. The ratios of the cis/trans isomers of 1 and 3 obtained from reactions in a range of solvents with various dielectric constants resulted in a little variation. However, addition of aqueous potassium halide solution to a DMSO-d₆ solution of 1 and 3 considerably increased the ratio of the cis/trans, respectively, indicating a strong intramolecular interligand Coulombic repulsion between the ionic phosphine ligands is present. Catalytic cyanation of aromatic iodide with KCN/ZnCl₂ in n-heptane/water biphasic system has been tested in the presence of 1–3 with base.     

A novel route for preparation of PtRuMe (Me = Fe,Co, Ni) and their catalytic performance for methanol electrooxidation

PtRuMe (Me = Fe, Co, Ni) catalysts dispersed on multi-wall carbon nanotubes (MWCNTs) were prepared by ultrasonic-assisted chemical reduction. X-ray diffraction (XRD) showed that Pt existed as face-centered cubic structure, while Ru and Me alloyed with Pt. The calculated particle sizes from XRD data are of 3.40, 3.40, 2.61 and 3.06 nm for PtRu, PtRuFe, PtRuCo and PtRuNi, respectively, and are consistent with TEM results. The electrochemical measurements showed that the addition of Me to PtRu enhances the electrocatalytic properties for methanol oxidation and PtRuNi has the best catalytic activity and stability.     

Solid solutions: An efficient way to control the temperature of spin transition in heterospin crystals MxCu1 − x(hfac)2L (M = Mn,Ni, Co; L = nitronyl nitroxide)

A series of mixed-metal solid solutions M_xCu_1 − x(hfac)₂L (M = Mn, Ni, and Co) liable to undergo thermally induced spin transitions have been synthesized. The structure and magnetic properties of the compounds have been investigated. By varying the metal to be incorporated in the complex (Mn, Ni, or Co) and the value of x, one can control the character of the magnetic anomaly.