Conversion of CuO Nanoplates into Porous Hybrid Cu2O/Polypyrrole Nanoflakes through a Pyrrole‐Induced Reductive Transformation Reaction

Porous hybrid Cu₂O/polypyrrole nanoflakes have been synthesized from solid CuO nanoplate templates through the pyrrole‐induced reductive transformation reaction at elevated temperature. The conversion mechanism involves the reductive transformation of CuO to Cu₂O and the in situ oxidative polymerization of pyrrole to polypyrrole. In addition, the morphology of the as‐converted nanohybrids depends on the shape of the CuO precursors. The strategy enables us to transform single‐crystalline CuO nanosheets into hollow hybrid Cu₂O/polypyrrole nanoframes. The ability to transform CuO and an organic monomer into porous hybrid materials of conducting polymer and Cu₂O with macrosized morphological retention opens up interesting possibilities to create novel nanostructures. Electrochemical examinations show that these porous hybrid Cu₂O/polypyrrole nanostructures exhibit efficient catalytic activity towards oxygen reduction reaction (ORR), excellent methanol tolerance ability, and catalytic stability in alkaline solution, thus making them promising nonprecious‐metal‐based catalysts for ORR in alkaline fuel cells and metal–air batteries.     

An In Situ Carbonization–Replication Method to Synthesize Mesostructured WO3/C Composite as Nonprecious‐Metal Anode Catalyst in PEMFC

A meostructured WO₃/C composite with crystalline framework and high electric conductivity has been synthesized by a new in situ carbonization–replication route using the block copolymer (poly(ethylene glycol)‐block‐poly(propylene glycol)‐block‐poly(ethylene glycol)) present in situ in the pore channels of mesoporous silica template as carbon source. X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetry differential thermal analysis, and N₂ adsorption techniques were adopted for the structural characterization. Cyclic voltammetry, chronoamperometry, and single‐cell test for hydrogen electrochemical oxidation were adopted to characterize the electrochemical activities of the mesoporous WO₃/C composite. The carbon content and consequent electric conductivity of these high‐surface‐area (108–130 m² g^?1) mesostructured WO₃/C composite materials can be tuned by variation of the duration of heat treatment, and the composites exhibited high and stable electrochemical catalytic activity. The single‐cell test results indicated that the mesostructured WO₃/C composites showed clear electrochemical catalytic activity toward hydrogen oxidation at 25 °C, which makes them potential non‐precious‐metal anode catalysts in proton exchange membrane fuel cell.     

Zirconia‐based Aerogels via Hydrolysis of Salts and Alkoxides: The Influence of the Synthesis Procedures on the Properties of the Aerogels

This contribution aims at evaluating different synthesis procedures leading to zirconia‐based aerogels. A series of undoped and yttrium‐doped zirconia aerogels have been prepared via hydrolysis and condensation reaction of different alkoxy‐ and different inorganic salt‐based precursors followed by supercritical drying. Well‐established but deleterious zirconium n‐propoxide (TPOZ) or zirconium n‐butoxide (TBOZ) were used as metal precursors in combination with acids like nitric acid and acetic acid as auxiliary agent for the generation of non‐yttrium stabilized zirconia aerogels. Yttrium‐stabilized zirconia aerogels as well as pure zirconia aerogels were obtained by the salt route starting from ZrCl₄ and crosslinking agents like propylene oxide or acetylacetone. The characteristics of the products were analyzed by nitrogen adsorption measurements, electron microscopy, and X‐ray scattering. It turned out that with respect to all relevant properties of the aerogels as well as the practicability of the synthesis procedures, approaches based on inexpensive non‐toxic salt precursors are the methods of choice. The salt‐based approaches allow not only for low‐cost, easy‐to‐handle synthesis procedures with realizable gelation times of less than 60 seconds, but also delivered the products with the highest surface area (449 m² g^?1 for ZrCl₄) within this series of syntheses.     

Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica

Immobilized nickel catalysts SBA*‐ L ‐x/Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N₃‐x. Related homogeneous ligand LtBu and its Ni^II complexes, [Ni( LtBu )(OAc)₂(H₂O)] ( LtBu /Ni) and [Ni( LtBu )₂]BF₄ (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐x/Ni suggests the formation of an inert [Ni L ₂] site on the surface at higher ligand loadings. SBA*‐ L ‐x/Ni has been applied to the catalytic oxidation of cyclohexane with m‐chloroperbenzoic acid (mCPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.     

Ultrasensitive electrochemical sensor for p-nitrophenyl organophosphates based on ordered mesoporous carbons at low potential without deoxygenization

p-Nitrophenyl organophosphates (OPs) including paraoxon, parathion and methyl parathion, etc, are highly poisonous OPs, for which sensitive and rapid detection method is most needed. In this work, an ultrasensitive electrochemical sensor for the determination of p-nitrophenyl OPs was developed based on ordered mesoporous carbons (OMCs) modified glassy carbon electrode (GCE) (OMCs/GCE). The electrochemical behavior and reaction mechanism of p-nitrophenyl OPs at OMCs/GCE was elaborated by taking paraoxon as an example. Experimental conditions such as buffer pH, preconcentration potential and time were optimized. By using differential pulse voltammetry, the current response of the sensor at −0.085 V was linear with concentration within 0.01–1.00 μM and 1.00–20 μM paraoxon. Similar linear ranges of 0.015–0.5 μM and 0.5–10 μM were found for parathion, and 0.01–0.5 μM and 0.5–10 μM for methyl parathion. The low limits of detection were evaluated to be 1.9 nM for paraoxon, 3.4 nM for parathion and 2.1 nM for methyl parathion (S/N = 3). Common interfering species had no interference to the detection of p-nitrophenyl OPs. The sensor can be applicable to real samples measurement. Therefore, a simple, sensitive, reproducible and cost-effective electrochemical sensor was proposed for the fast direct determination of trace p-nitrophenyl OPs at low potential without deoxygenization.     

Preparation of Anatase Hollow TiO2 Spheres and Their Photocatalytic Activity in the Photodegradation of Chlorpyrifos

Hollow anatase titania (TiO₂) spheres were synthesized using fructose and tetrabutyl titanate (Ti(OC₄H₉)₄, TBT) as the precursors via the conventional hard template method. The morphological, structural and thermal properties of the products were characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG‐DTA), Brunauer? Emmett? Teller (BET) surface area analysis and diffuse reflectance ultraviolet visible (DR UV? Vis) spectroscopy. XRD revealed that the hollow TiO₂ prepared was in the anatase phase and the BET surface area measured was about 22 m² g^?1. The photocatalytic activity of the synthesized hollow anatase TiO₂ in the photodecomposition of chlorpyrifos was 18.67 % higher than that obtained using commercial TiO₂.     

载体对Ni_2P催化剂加氢脱氮反应性能的影响

使用TiO2、Al2O3以及TiO2-Al2O3复合载体考察了载体对磷化镍催化剂活性相和加氢脱氮性能的影响。不同钛铝原子比的TiO2-Al2O3复合载体采用原位-溶胶凝胶法制备,负载的磷化镍催化剂采用等体积浸渍法和H2原位还原法制备。以喹啉为模型化合物在固定床反应器上对催化剂的加氢脱氮性能进行评价,采用XRD、N2吸附、TEM和H2-TPR等技术对催化剂和载体进行了表征。结果表明,制成的复合载体基本保留了最初引入的γ-Al2O3的孔特征,分散在γ-Al2O3表面的TiO2以锐钛矿晶型存在。不同载体对催化剂的H2还原行为有显著影响,所形成的活性物种也不相同。Al2O3中引入TiO2可以减弱P物种和Al2O3之间的相互作用,有利于Ni2P活性相的生成和催化活性的提高。当Ti/Al的原子比为1∶8时,Ni2P/TiO2-Al2O3催化剂比Ni2P/TiO2、Ni2P/Al2O3催化剂具有更高的加氢脱氮活性。     

掺氮介孔炭作为双功能材料用于氧还原与超级电容器

以壳聚糖为含氮碳源,正硅酸乙酯为软模板,硝酸镍为催化剂,通过简单的低温水热法及后续炭化,成功合成出掺氮介孔炭材料（NMC-1）.NMC-1含有多孔结构以及氮氧等杂原子,能提高其电催化性能、双电层电容与赝电容.由于NMC-1在碱液中表现出显著的催化氧还原反应活性和具有较高的超级电容器比电容（在0.2A/g时为252F/g）及好的循环稳定性,因此,它有可能作为一种可再生、环保的双功能材料同时应用于燃料电池与超级电容器领域.     

Synthesis of spinel lithium titanate anodes incorporated with rutile titania nanocrystallites by spray drying followed by calcination

Lithium insertion into spinel Li₄Ti₅O₁₂ incorporated with rutile TiO₂ was investigated in order to clarify the redox mechanism responsible for the first plateau at 1.5 V vs. Li/Li⁺. Spherical Li₄Ti₅O₁₂ powders with an average diameter of 2-3 μm can be achieved by spray drying followed by sintering process. The Li/Ti molar ratio in the precursor is selected as the factor for preparing spinel Li₄Ti₅O₁₂ powders with different concentrations of rutile TiO₂. The specific capacity from the first plateau at 1.5 V contributes to the major portion in the overall capacity. The rutile TiO₂ in spinel Li₄Ti₅O₁₂ anodes tends to improve the specific capacity at the first plateau. This can be attributed to two possible reasons: (i) rutile TiO₂ provides an additional number of sites (i.e., oxygen octahedral vacancy in rutile TiO₂) for the Li insertion, and (ii) less amount of residual Li oxides results in high electronic conductivity. The Li₄Ti₅O₁₂ anodes display high rate capability with low irreversible capacity, indicating good reversibility of insertion/de-insertion of Li ions. The results presented in this work show unambiguously that the presence of rutile TiO₂ in spinel Li₄Ti₅O₁₂ has a positive effect on the performance promotion of Li₄Ti₅O₁₂ anodes.