Intercalated polyaniline–kaolinite nanocomposite prepared via in situ mechanochemical synthesis

The in situ polymerization of aniline monomers within kaolinite interlayers easily led to an intercalated polyaniline (PANI)–kaolinite nanocomposite through a facile mechanochemical method. The X‐ray diffraction results demonstrate that PANI was successfully intercalated in the interlayers of kaolinite, which was lightened by an increased basal spacing from 7.24 to 14.67 Å of kaolinite in the as‐synthesized nanocomposite, and the characterization results from Fourier transform infrared spectrometry, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy further confirm this conclusion. The thermal stability of PANI was improved significantly when PANI was intercalated into kaolinite to form the nanocomposite; this was proven by thermogravimetric analysis. Moreover, a panel experiment was carried out under a simulated marine environment to evaluate the anticorrosive effect of the as‐prepared product, and the results show that the epoxy resin/intercalated PANI–kaolinite nanocomposite coating had a better anticorrosive effect than that of the neat epoxy resin coating. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43551.     

Multiferroic bismuth manganite prepared by mechanochemical synthesis

Multiferroic bismuth manganite (BiMnO₃) is known as a material that exhibits both ferromagnetic and ferroelectric properties making it interesting for various technological applications. Unfortunately, preparation of BiMnO₃ is not possible by a conventional solid-state reaction and it can form only from mixture of oxides at high pressures (>40 kbar).In this work single-phased BiMnO₃ was prepared for the first time by mechanochemical synthesis in a planetary ball mill. A mixture of Bi₂O₃ and Mn₂O₃ was intensively milled in air atmosphere, using stainless steel vials and balls. According to analysis of XPRD results BiMnO₃ obtained after milling for 240 min has a tetragonal structure with lattice parameters a = 3.9230 Å, c = 3.920 Å and a crystallite size of 16.8 nm. The cumulative energy introduced into the system during milling for 240 min was 401 kJ/g. It was found that the obtained powders were agglomerated. Corresponding agglomeration factors were calculated from the results of BET and particle size distribution analysis.     

Anion doped bimetallic selenide as efficient electrocatalysts for oxygen evolution reaction

The development of highly efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is of great importance in advancing the practical applications of green and sustainable hydrogen energy. Doping with either cations or non-metallic anions is a typical strategy used to improve the electrocatalytic activity for OER catalysts. In this study, an anion doped bimetallic selenide Co_0.75Fe_0.25(S_0.2Se_0.8)₂ solid solution is prepared via the simultaneous sulfuration and selenylation of a scalably produced CoFe-layered double hydroxide (CoFe-LDH) precursor, using commercially available sulfur and selenium powders as S and Se sources, respectively. Electrocatalytic test shows that the anion doped bimetallic selenide Co_0.75Fe_0.25(S_0.2Se_0.8)₂ electrode requires an overpotential of 293 mV and a low Tafel slope of 77 mV dec⁻¹ at a current density of 10 mA cm⁻² in an alkaline media, and it exhibits the significantly enhanced electrocatalytic performance for the OER compared with its counterparts of Co_0.75Fe_0.25S₂ and Co_0.75Fe_0.25Se₂. The enhanced electrocatalytic performance is supported experimentally by the results of charge-transfer resistance and electrochemically active surface area. Our LDH precursor-based protocol can provide a strategy to prepare non-metallic anion doped bimetallic selenides as efficient electrocatalysts for water splitting.     

Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt.The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.     

用于PEMFC的介孔碳担载铂氧化钨电催化剂的制备与表征

利用介孔碳作为载体,制备介孔碳担载Pt-WO3复合催化剂应用于质子交换膜燃料电池（PEMFC）电极.以苯为碳源,采用气相沉积法复制介孔SiO2Al-SBA-15模板结构合成石墨化介孔碳Cg,采用浸渍法制备无定形介孔碳CMK-3.通过分步沉积,将Pt和WO3担载到介孔碳载体上,采用比表面分析（BET）、X线衍射（XRD）、透射电子显微镜（TEM）、循环伏安法以及单电池极化性能测试对介孔碳担载的复合催化剂进行表征.结果表明：介孔碳作为催化剂载体,其孔道结构有助于催化剂的均匀分散,从而提高催化剂的电催化剂活性.由于石墨化介孔碳的导电性能高于无定形介孔碳,因此Pt-WO3/Cg比Pt-WO3/CMK-3具有更好的电极催化活性.     

Structural and transport properties of neodymium tungstates prepared via mechanochemical activation

Nd_5.5WO_11.25-δ, (Nd_5/6La_1/6)_5.5WO_11.25-δ and Nd_5.5W_0.5Mo_0.5O_11.25-δ mixed oxides have been prepared using mechanochemical activation (MA) of Nd₂O₃-WO₃, Nd₂O₃-La₂O₃-WO₃, Nd₂O₃-MoO₃-WO₃ mixtures in a high-power planetary ball mill. Genesis of these tungstates structural properties was studied by XRD, SEM, TEM with EDX analysis, ¹H NMR, IR and Raman spectroscopy. X-ray diffraction has revealed that MA results in formation of a pure fluorite structure already after milling. High-density ceramic pellets have been obtained after sintering at 1350?°C. Transport properties of Nd_5.5WO_11.25-δ mixed oxide were improved by the partial substitution of Nd with La in (Nd_5/6La_1/6)_5.5WO_11.25-δ and W with Mo in Nd_5.5W_0.5Mo_0.5O_11.25-δ samples. For all samples the electrical conductivity values measured in a humid atmosphere (up to ~ 10^?3 S/cm at 550?°C) exceed those measured in a dry atmosphere indicating the proton character of conductivity.     

Unsupported CuFe bimetallic nanoparticles for higher alcohol synthesis via syngas

CuFe bimetallic nanoparticles were synthesized by co-reduction method as model catalysts for HAS. Cu contacted with Fe component in the form of Cu–Fe alloy, CuFe₂O₄ and Cu(Fe)–CuFe₂O₄ interface in the fresh CuFe sample. However, Cu/Fe₃O₄ and Cu/FeC_x composites formed after activation. Cu–FeC_x center benefited alcohol formation which led to higher selectivity to total alcohol for CuFe than that for Fe and physical mixture of Fe and Cu nanoparticles. In addition, CuFe showed very high C_6 +OH selectivity in alcohol distribution and 33 wt.%–74 wt.% was achieved, demonstrating the potential for direct synthesis of C_6 +OH from syngas.     

MgAl2O4 spinel prepared by mechanochemical synthesis used as a support of multimetallic catalysts for paraffin dehydrogenation

The catalytic performance in n-butane dehydrogenation of bimetallic PtSn, PtGa and PtIn, and trimetallic PtSnIn and PtSnGa catalysts (with low metal contents) supported on a MgAl₂O₄ prepared by a novel mechanochemical synthesis was evaluated both in flow and pulse equipment. The influence of the addition of different promoters (Sn, Ga and In) to Pt on the activity, selectivity and deactivation in the n-butane dehydrogenation reaction was studied. Stability experiments through successive reaction-regeneration cycles were carried out for selected catalysts. In order to correlate the properties of the metallic phase of the catalysts with the catalytic behavior, several characterization techniques were used, such as test reactions of the metallic phase (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), TPR, XPS, H₂ chemisorption and TEM. Bimetallic PtSn catalyst has a better catalytic behavior than PtIn and PtGa ones. For PtSnM (M: In or Ga) catalysts, whereas Ga addition to the bimetallic catalyst does not practically modify the dehydrogenation performance, the addition of In produces an increase of the activity and the selectivity to butenes. Characterization results indicate the presence of geometric effects for the PtSn catalyst, and geometric and electronic effects for PtIn and PtGa ones. For trimetallic catalysts, the presence of a close contact between Pt, Sn and In or Ga in both trimetallic catalysts was found, mainly due to geometric effects like blocking and dilution of the active sites by the promoters. In stability experiments, the trimetallic PtSnIn/MgAl₂O₄ catalyst clearly displays the best catalytic performance along reaction-regeneration cycles, though PtSnGa and PtSn catalysts also showed a very good behavior through the successive cycles. The characterization of these catalysts after cycles shows that their metallic phases are slightly modified along the cycles.     

Ethanol membrane reformer and PEMFC system for automotive application

The wide diffusion of fuel cell (FC) powered Zero-Emissions Vehicles (ZEVs) is stopped by hydrogen storage technological drawbacks, as high cost and low storage volume density. This obstacle can be overcome if a fuel processor, able to produce H₂ to be fed to FC from a liquid fuel, is installed. In the present work, an innovative clean power generator for light-vehicles is presented, modelled and designed. Such a generator is realized by coupling the most market-appeal clean liquid fuel, the ethanol, and the most technologically strengthened and the only off-the-shelf fuel cell type, the PEMFC, by applying a membrane reactor (MR) for converting ethanol and separating the hydrogen produced in one single and compact device.A process scheme is described and a 4-tubes-and shell membrane reactor is modelled by means of a rigorous homogeneous 2D mathematical model, validated by experimental data.The effect of most important operating conditions, as gas mixture residence time, heating fluid temperature, steam-to-ethanol and sweeping-to ethanol ratios, operating pressure, is evaluated via simulation and optimal conditions are defined. Then, by applying the optimal conditions set, a design of ethanol MR + PEMFC system in substitution of a 4 kW Pb-battery pack for a light vehicle is proposed.Final results attest that a 1.52 m long, 0.4 m large 4-tubes-and-shell membrane reactor (total volume equal to 0.76 m³) is able to produce 64.7 NL/min of hydrogen, equal to the 4 kW FC feedstock requirement. The MR ethanol conversion is 98% and the percentage of H₂ recovered through the Pd-Ag selective membrane on total H₂ produced in the reactor is 67% about.     

Combustion synthesis of porous Ti-Co alloys for orthopedic applications

A mechanoactivation of Ti-Co mixtures was used to perform the SHS of Ti-Co alloys without preheating and heat-generating additives. The SHS of Ti-Co alloys from non-activated Ti + Co green mixtures containing an admixture of B₄C as a heat-generating agent without preliminary heating was carried out for the first time. The phase composition, structure, and mechanical properties of synthesized materials were explored upon variation in [B₄C] within the range 2–10 wt %. The desired structure/properties of combustion products were attained at [B₄C] = 2–4 wt %. The materials synthesized under the above optimal conditions exhibited a developed and uniformly distributed system of pores (largely open) with a size of 150–400 μm, at a wall thickness of 70–100 μm. By their properties (interconnected pores in the range 200–500 μm, compression strength 40–65 MPa), the synthesized materials can be recommended for use as metallic scaffolds intended for bone tissue ingrowths.      

Ionic and electronic transport in calcium-substituted LaAlO3 perovskites prepared via mechanochemical route

The present work explores mechanosynthesis of lanthanum aluminate-based perovskite ceramics and corresponding effects on ionic-electronic transport properties. La_1-xCa_xAlO_3-δ (x = 0.05–0.20) nanopowders were prepared via one-step high-energy mechanochemical processing. Sintering at 1450 °C yielded dense ceramics with submicron grains. As-prepared powders and sintered ceramics were characterized by XRPD, XPS and SEM. Electrochemical studies showed that partial oxygen-ionic conductivity in prepared La_1-xCa_xAlO_3-δ increases with calcium content up to 10 at.% in the lanthanum sublattice and then levels off at ∼6 × 10⁻³ S/cm at 900 °C. La_1-xCa_xAlO_3-δ ceramics are mixed conductors under oxidizing conditions and ionic conductors with negligible contribution of electronic transport in reducing atmospheres. Oxygen-ionic contribution to the total conductivity is 20–68% at 900 °C in air and increases with Ca content, with temperature and with reducing p(O₂). Impedance spectroscopy results showed however that electrical properties of mechanosynthesized La_1-xCa_xAlO_3-δ ceramics below ∼800 °C are determined by prevailing grain boundary contribution to the total resistivity.     

Exfoliated graphene-supported Pt and Pt-based alloys as electrocatalysts for direct methanol fuel cells

To greatly improve the electrocatalytic activity for methanol oxidation, high-quality exfoliated graphene decorated with uniform Pt nanocrystals (NCs) (3 nm) have been prepared by a very simple, low-cost and environmentally benign process. During the entire process, no surfactant and no halide ions were involved, which not only enabled very clean surface of Pt/graphene leading to excellent conductivity, but also greatly improved the electrocatalyst tolerance to carbon monoxide poisoning (Pt/graphene, I_f/I_b = 1.197), compared to commercial Pt/C (I_f/I_b = 0.893) catalysts. To maximize the electrocatalytic performance and minimize the amount of precious Pt, Pt–M/graphene (M = Pd, Co) hybrids have also been prepared, and these hybrids have much larger electrochemically active surface areas (ECSA), which are 4 (PtPd/graphene) and 3.3 (PtCo/graphene) times those of commercial Pt/C. The PtPd/graphene and PtCo/graphene hybrids also have remarkably increased activity toward methanol oxidation (I_f/I_b = 1.218 and 1.558). Furthermore, density functional theory (DFT) simulations demonstrate that an electronic interaction occurred between Pt atoms and graphene, indicating that graphene substrate plays a crucial role in regulating the electron structure of attached Pt atom, which confirmed that the increased efficiency of methanol oxidation was due to the synergetic effects of the hybrid structure.     

Palygorskite sheets prepared via tape casting for wound healing applications

The main objective was to increase the applicability of palygorskite by palygorskite sheets using a tape casting method. The stability of the suspension was investigated and the tapes were characterized by TGA/DTA, XRD, and SEM-FEG. The antimicrobial activity was analyzed in order to test the applicability of a newly modified drug release system that incorporates neomycin in palygorskite. Preliminary results showed that the palygorskite sheet prepared via the tape casting is promising for wound healing applications.     

Sputtered iridium oxide films as electrocatalysts for water splitting via PEM electrolysis

Thin films of iridium oxide deposited by reactive magnetron sputtering have been investigated as catalysts for electrochemical water splitting in a polymer electrolyte membrane (PEM) cell. The sputtered films possess excellent mechanical stability and corrosion resistance at the high anodic potentials where oxygen evolution takes place. Their catalytic activity has been assessed using the conventional electrochemical methods of cyclovoltammetry and steady state polarisation techniques. A morphology factor assessing the catalyst active surface for a series of sputtered samples with varying thickness/loading has been determined and correlated to the catalytic efficiency. It has been proven that iridium oxide is a very efficient catalyst for oxygen evolution reaction (OER). The best performance with anodic current density of 0.3 A cm⁻² at potential of 1.55 V (versus RHE) has shown the 500 nm thick film containing 0.2 mg cm⁻² catalyst. The results obtained have also demonstrated the advantages of the reactive magnetron sputtering as simple and reliable method for deposition of efficient and cost effective catalysts for PEM electrolysis application.     

Nanometric bimetallic sulfides prepared via thermal decomposition of Ni and Fe heteropolymolybdate emulsions

NiMo and FeMo nanometric particles were prepared by thermal decomposition of water in oil emulsions, where the aqueous phase was a solution of iron or nickel heteropolymolybdates. Decomposition experiments were carried out at 573 K and 70 Bar of hydrogen, with carbon disulfide added to the emulsions. Solids were characterized by X ray diffraction, confocal microscopy and BET surface area. Thiophene hydrodesulfurization was performed in a continuous flow microreactor at 553 K and 1.0 Bar. Particles with diameters between 370 and 560 nm were obtained, and thiophene HDS was in the order NiMoS > MoS ≈ FeMoS > NiS > FeS. The feasibility of using thermal decomposition of emulsions to obtain nanometric bimetallic sulfides particles was shown.     

Effect of pH on PtRu electrocatalysts prepared via a polyol process on carbon nanotubes

This paper reports a study on the pH effects on the PtRu nanoparticles synthesized in a polyol process that were deposited on carbon nanotubes (CNTs) by reducing metal salts using ethylene glycol at various pHs. It was found that the nanoparticle size, composition, and catalytic activity all were sensitive to pH. The nanoparticles decreased in size as the preparation pH increased from 1.6 to 10.0, with the largest size at 2.47 nm and the smallest at 1.13 nm. An exception was found for pH at 0.7, which resulted in an average size of only 1.01 nm. Preparation pH was found to affect polyol reaction mechanisms, which are believed to be dominated by direct metal reduction at low pH and by both direct metal reduction and hydroxide reduction at high pH. However, at high pH the reactions were limited by hydroxide reductions, and longer reaction durations were needed to fully deposit the metals. To study the pH effect on the electrochemical activity of the catalysts, CO stripping techniques were used to determine peak potentials and active surface areas. Together with cyclic voltammetry in the electro-oxidation of methanol, it was found that the catalyst prepared at pH 8.4 has the best performance.     

Preparation of cost-effective Pt–Co electrodes by pulse electrodeposition for PEMFC electrocatalysts

Low loading platinum–cobalt (Pt–Co) cathode catalyst on a Nafion(Na⁺)-bonded carbon layer is fabricated by using galvanostatic pulse technique to show the advantage of electrodeposition for high utilization of catalyst in proton exchange membrane fuel cell (PEMFC). We observed that Pt–Co catalysts evenly exist on the surface of carbon electrode and its thickness is about 5.8 μm, which is four times thinner than conventional Pt/C. Improved single cell power performance of Pt–Co cathode catalysts with a ratio of 3.2:1 compared with Pt/C is clearly presented.