多孔Co3O4纳米纤维用于锂-空气电池高性能正极催化剂

采用静电纺丝技术结合高温煅烧方法,以乙酰丙酮钴(Co(C₅H₇O₂)₃)为前驱物,制备了由Co₃O₄纳米颗粒组成的多孔纳米纤维(Co₃O₄ NFs),其比表面积高达83 m2·g?1,并将制得的多孔Co₃O₄ NFs用于锂-空气电池催化剂。多孔Co₃O₄ NFs为电池反应提供了充足的活性位点及反应物的传输通道,有利于电池反应的顺利进行,使电池的放电容量得到极大地提高。另外,Co₃O₄催化剂的加入提高了电极的催化活性,较大程度降低了电池的过电位。值得注意的是,Co₃O₄催化剂的加入同时调控了锂-空气电池放电产物Li₂O₂的形貌,得到的放电产物Li₂O₂尺寸更小,在电极表面分布更为均匀,该形态的Li₂O₂在充电过程中更容易被分解,有利于提高电池的充电效率,同时电极的体积效应也可得到极大缓解。得益于以上优势,基于多孔Co₃O₄ NFs/炭黑Super P (Co₃O₄ NFs/SP)正极的锂-空气电池的电化学性能得到较大提高,50 mA·g?1电流密度下Co₃O₄ NFs/SP的放电容量高达10600 mA·h·g?1,电池可实现100次的充放电循环。      

四氧化三钴/碳纳米管薄膜的水热合成及其储锂性能

以5-磺基水杨酸和戊二酸为螯合和氧化试剂,在水热条件下将硫酸钴氧化成纳米级Co₃O₄。以碳纳米管薄膜为载体将Co₃O₄颗粒紧密地附着在碳纳米管上使其填充入碳纳米管薄膜的空隙生成Co₃O₄/碳纳米管复合材料薄膜(Co₃O₄@CNTs),并研究其储锂性能。电化学测试结果表明,Co₃O₄@CNTs薄膜具有较高的放电比容量和优异的倍率性能,在0.2C倍率下初始放电比容量高达1712.5 mAh·g^-1,100圈循环后放电比容量为1128.9 mAh·g^-1的;在1C倍率下100圈循环后放电比容量仍然保持527.8 mAh·g^-1。Co₃O₄@CNTs薄膜优异的性能源于Co₃O₄与CNTs的协同作用。高分散性的Co₃O₄增大了活性材料与电解液之间的接触面积,CNTs有助于形成良好的导电网络提高电子电导率,进而提高了Co₃O₄负极材料的循环性能和倍率性能。     

Zn2+诱导棱柱状四氧化三钴的制备及在葡萄糖传感器中的应用

以硝酸钴、硝酸锌、尿素、氟化铵为原料,泡沫镍为基体,在水热法的基础上,利用两性金属的特点,通过引入Zn²⁺离子,并结合碱洗过程,在泡沫镍基体表面合成了高纯度独特的棱柱状Co₃O₄纳米团簇纤维。制备的Co₃O₄/Ni电极的形貌及成分通过扫描电子显微镜与X射线衍射进行了表征,电极的电化学性能利用循环伏安法与计时电流法测试,测试均在1mol/L KOH溶液中进行。结果表明:利用Zn²⁺诱导在泡沫镍表面制备的Co₃O₄呈现一种棱柱状纳米团簇纤维结构。这种结构的Co₃O₄纳米材料具有高的比表面积,在对葡萄糖检测过程中表现出优越的电化学性能,当其作为电极,表现出检测灵敏度高[23430μA/(mmol/L·cm²)],检出限低(1.547μmol/L)和线性检测范围宽(0~2.75mmol/L)的特点。抗干扰实验在+0.5Vvs.SCE进行,结果显示制备的Co₃O₄/Ni电极对葡萄糖具有优异的选择性。因此可应用于无酶葡萄糖传感器的电极材料来改善现有无酶葡萄糖传感器材料响应范围小,灵敏度低等问题。     

核壳材料Co3O4@SiO2催化环己基过氧化氢分解

环己基过氧化氢(CHHP)分解是环己烷无催化氧化工艺制备环己醇和环己酮的重要反应步骤.本研究以Co3O4纳米颗粒为内核,十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸四乙酯(TEOS)为硅源,采用模板法制备了核壳结构材料Co3O4@SiO2.考察了SiO2壳层制备条件:乙醇和水的比例、CTAB的浓度和TEOS的用量对...     

Stabilizing Co3O4 nanorods/N-doped graphene as advanced anode for lithium-ion batteries

Tricobalt tetroxide (Co₃O₄) is one of the promising anodes for lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the poor electrical conductivity and the rapid capacity decay hamper its practical application. In this work, we design and fabricate a hierarchical Co₃O₄ nanorods/N-doped graphene (Co₃O₄/NG) material by a facile hydrothermal method. The nitrogen-doped graphene layers could buffer the volume change of Co₃O₄ nanorods during the delithium/lithium process, increase the electrical conductivity, and profit the diffusion of ions. As an anode, the Co₃O₄/NG material reveals high specific capacities of 1873.8 mA·h·g⁻¹ after 120 cycles at 0.1 A·g⁻¹ as well as 1299.5 mA·h·g⁻¹ after 400 cycles at 0.5 A·g⁻¹. Such superior electrochemical performances indicate that this work may provide an effective method for the design and synthesis of other metal oxide/N-doped graphene electrode materials.     

Co2Ni1O4/不锈钢复合材料的制备及其电催化析氧性能

电解水包括析氢反应(HER)与析氧反应(OER),由于OER是复杂的4电子转移过程,制作出具有优异耐久性的高活性的非贵金属OER电催化剂对于电解水至关重要。为了降低成本,选择304型不锈钢网(SS)作为基体,使用电沉积的方法制备钴-镍双氢氧化物,利用真空煅烧的方法制备钴-镍氧化物。使用XRD、SEM、TEM、XPS和电化学工作站对Co₂Ni₁O₄/SS复合材料的晶体结构、形貌和电催化OER性能进行了研究。结果表明:电沉积制备的钴-镍双氢氧化物煅烧之后转变成尖晶石结构的钴-镍氧化物;在不锈钢表面成功合成了大量密集的层状结构;在1.0 mol/L KOH电解液中,Co₂Ni₁O₄/SS电极表现出优异的OER电催化性能,达到10 mA·cm?2电流密度时所需要的过电位仅为240 mV,Tafel斜率为53.92 mV·dec?1,并且表现出优异的稳定性。      

四氧化三钴阵列材料的制备及电化学性质研究

以酸化后的高导电柔性碳布为基底,通过电化学沉积及辅助热处理技术在碳布表面均匀地生长了规整排列的四氧化三钴(Co₃O₄)纳米片材料,纳米片厚度约为15nm,片层之间相互交织,形成三维网络多孔结构。这种独特的结构不仅增加了Co₃O₄纳米材料的有效利用率,而且缩短了电解质离子的传输通道,加速了其倍率性能。期待该材料成为组装高性能柔性电容器器件的备选电极材料。     

Robust Co3O4 nanocatalysts supported on biomass-derived porous N-doped carbon toward low-pressure hydrogenation of furfural

The catalytic conversion of biomass platform chemicals using abundant non-noble metal nanocatalysts is a challenging topic. Here, high-density cobalt oxide nanoparticles loaded on biomass-derived porous N-doped carbon (NC) was fabricated by a tandem hydrothermal pyrolysis and mild nitrate decomposition process, which is a green and cheap preparation method. The Co₃O₄ nanoparticles with the average size of 12 nm were uniformly distributed on the porous NC. The nanocomposites also possessed large surface area, high N content, good dispersibility in isopropanol, and furfural absorbability. Due to these characteristics, the novel cobalt nanocatalyst exhibited high catalytic activity for producing furfuryl alcohol, yielding 98.7% of the conversion and 97.1% of the selectivity at 160 °C for 6 h under 1 bar H₂. The control experiments implied that both direct hydrogenation and transfer hydrogenation pathways co-existed in the hydrogenation reaction. The excellent catalytic activity of Co₃O₄@NC was attributed to the cooperative effects of porous NC and Co₃O₄ nanoparticles. This approach provides a new idea to design effective high-density non-noble metal oxide nanocatalysts for hydrogenation reactions, which can make full use of sustainable natural biomass.     

High-resolution and analytical transmission electron microscopy of epitaxial YBa2Cu3O7−x thin films and YBa2Cu3O7/PrBa2Cu3O7 superlattices

Transmission electron microscopy (TEM) studies of epitaxial YBa₂Cu₃O_7−x thin films and YBa₂Cu₃O₇/PrBa₂Cu₃O₇ superlattices are summarized. High-resolution imaging of cross-sections and plan views and energy-dispersive X-ray microanalysis and electron energy loss spectroscopy in the transmission electron microscope were the methods applied. In the first section results on YBa₂Cu₃O_7−x thin films With varying oxygen stoichiometry deposited onto SrTiO₃ are discussed. Then, YBa₂Cu₃O₇/PrBa₂Cu₃O₇ superlattices deposited onto SrTiO₃ and MgO are investigated. Finally, an interface analysis of high-quality YBa₂Cu₃O_7−x thin films deposited onto sapphire with yttrium-stabilized zirconia buffer layers is presented.     

Formation of MgAl2O4 in Al2O3-(Al-4wt.%Mg) composites

The Al₂O₃ particles are introduced into the Al-4wt.%Mg melt by the “vortex” method. After being cast, Al₂O₃-(Al-4wt.%Mg) composites are remelted at 700, 750, 800 and 850°C for different residence times to investigate the formation of MgAl₂O₄ (spinel).

The results show that MgAl₂O₄ is the unique interface of the Al₂O₃-(Al---Mg) composites held at 700–850°C. Fine MgAl₂O₄ crystals grow on the surface of the Al₂O₃ particle but, as the holding temperature and the residence time increase, some spinels will form themselves into pyramidal shape. The MgAl₂O₄ grows not only at the matrix-particle interface but also on the surface of the composite specimens. The formation reactions of interfacial MgAl₂O₄ are as follows: Mg(1) + 2Al(1) + 2O₂(g) = MgAl₂O₄(s)3Mg(1) + 4Al₂O₃(s) = 3MgAl₂O₄(s) + 2Al(1) Both of them are equally important.     

Conducting polymer PEDOT:PSS coated Co3O4 nanoparticles as the anode for sodium-ion battery applications

Metal oxides are considered as potential anodes for sodium-ion batteries (SIBs). Nevertheless, they suffer from poor cycling and rate capability. Here, we investigate conductive polymer coating on Co₃O₄ nanoparticles varying with different percentages. X-ray diffraction, electron microscopy and surface chemical analysis were adopted to analyze coated and uncoated Co₃O₄ nanoparticles. Conducting polymer, poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS), has been utilized for coating. Improved specific capacity and rate capability for an optimal coating of 0.5 wt.% were observed. The 0.5 wt.% coated sample outperformed the uncoated one in terms of capacity, rate capability and coulombic efficiency. It delivered a reversible capacity of 561 mAh·g⁻¹ at 100 mA·g⁻¹ and maintained a capacity of 318 mAh·g⁻¹ at a high rate of 1 A·g⁻¹. Increasing the PEDOT:PSS coating percentage led to lower performance due to the thicker coating induced kinetic issues. Ex-situ analysis of the 0.5 wt.% coated sample after 100 cycles at 1 A·g⁻¹ was characterized for performance correlation. Such a simple, cost-effective and wet-chemical approach has not been employed before for Co₃O₄ as the SIB anode.     

Fe-doped NiCo2O4 hollow hierarchical sphere as an efficient electrocatalyst for oxygen evolution reaction

We prepared porous Fe-doped nickel cobaltate (Fe-NiCo₂O₄) hollow hierarchical nanospheres through a facile self-templated synthetic strategy. Due to the porous hollow structure and composition, the Fe-NiCo₂O₄ presented vastly superior electrocatalytic activity for the oxygen evolution reaction (OER), compared with NiCo₂O₄ and the majority of other OER catalysts. With an aim of stimulating a current density of 10 mA·cm⁻², the Fe-NiCo₂O₄ catalyst needs an overpotential of 210 mV, which is on a par with the general properties of commercial IrO₂. In addition, the Fe-NiCo₂O₄ catalyst performed stably in long-term testing. The excellent activity and long-term stability showed that such catalysts have great promise for widespread application in the field of water splitting.     

可磁分离Fe3O4/g-C3N4复合材料的制备及其性能

为了利用Fe₃O₄的磁响应性及石墨相C₃N₄（g-C₃N₄）优良的光催化活性,首先采用高温热聚合法,以尿素为前驱体制备g-C₃N₄,然后采用水热法合成了可磁分离Fe₃O₄/g-C₃N₄复合材料。利用TEM、XRD、TGA、BET和振动样品磁强计（VSM）等多种测试手段表征分析Fe₃O₄/g-C₃N₄复合材料的形貌、晶型结构、比表面积、成分、饱和磁化强度等。通过模拟太阳光下Fe₃O₄/g-C₃N₄复合材料光催化吸附降解亚甲基蓝（MB）的实验,评价了Fe₃O₄/g-C₃N₄复合材料的吸附性能及光催化性能。结果表明,可磁分离Fe₃O₄/g-C₃N₄复合材料具有较大的比表面积,约为71.89 m²/g;且具有较好的磁性,饱和磁化强度为18.79 emu/g,可实现复合材料的分离回收;光照240 min时,Fe₃O₄/g-C₃N₄复合材料对MB的去除率为56.54%。所制备的Fe₃O₄/g-C₃N₄复合材料具有优良的吸附性能、光催化活性和磁性,并可通过外加磁场进行分离与回收。     

La2O3添加对MgAl2O4-CaAl4O7-CaAl12O19复合材料烧结行为的影响

为适应材料轻量化的发展需要,在1 400~1 600℃温度下开发了MgAl₂O₄-CaAl₄O₇-CaAl₁₂O₁₉（MA-CA₂-CA₆）复合材料,并考察了La₂O₃添加对该复合材料烧结行为、显微结构和力学性能的影响。结果表明,La₂O₃添加剂优先固溶到MA-CA₂-CA₆复合材料组成晶相CA₆中,促使CA₆相发生晶格畸变,有效抑制了CA₆晶粒沿基面的异常长大,其形貌由片状向等轴状趋势转变,促使MA-CA₂-CA₆复合材料制备过程中由于CA₆晶粒异常长大而导致的多孔网状显微结构得以有效消除,因此也极大地改善了Mg²⁺的扩散条件,在一定程度上间接促进了MA晶粒的发育,有效促进了MA-CA₂-CA₆复合材料的烧结。经1 200℃预烧、1 600℃保温2 h烧成后,当La₂O₃的添加量为4wt%时,MA-CA₂-CA₆复合材料试样的显气孔率由19.2%下降至6.1%,体积密度由2.78 g/cm³上升至3.18 g/cm³,制得了MA、CA₂、CA₆晶相呈现交织分布、显微结构致密、有利于其力学性能改善的La₂O₃/MA-CA₂-CA₆复合材料,经1 200℃预烧、-1 600℃保温2 h烧成后的4wt% La₂O₃添加试样,其冷态抗压强度由317 MPa增加到了501 MPa。     

Microstructural, photocatalysis and electrochemical investigations on CeTi2O6 thin films

The properties of sol–gel derived CeTi₂O₆ thin films deposited using a solution of cerium chloride heptahydrate and titanium propoxide in ethanol are discussed. The effect of annealing temperature on structural, optical, photoluminescence, photocatalysis and electrochemical characteristics has been examined. Lowest annealing temperature for the formation of crystalline CeTi₂O₆ phase in these samples is identified as 580 °C. The optical transmittance of the films is observed to be independent of the annealing temperature. The optical energy bandgap of the 600 °C annealed film for indirect transition is influenced by the presence of anatase phase of TiO₂ in its structure. Fourier transform infrared spectroscopy investigations have evidenced increased bond strength of the Ti–O–Ti network in the films as a function of annealing temperature. The photoluminescence intensity of the films has shown dependence on the annealing temperature with the films fired at 450 °C exhibiting the maximum photoluminescence activity. The decomposition of methyl orange and eosin (yellow) under UV–visible light irradiation in the presence of crystalline CeTi₂O₆ films shows the presence of photoactivity in these films. The photocatalytic response of CeTi₂O₆ films is found to be superior to the TiO₂ films. In comparison to crystalline films, the amorphous films have shown superior electrochemical characteristics. The 500 °C annealed amorphous films have exhibited the most appropriate properties for incorporation in electrochromic devices comprising tungsten oxide as the primary electrochromic electrode.     

Fe3O4/MnO2磁性复合氧化物催化剂的制备及性能

具有磁性的非均相催化剂价格低廉、低污染、高能效、容易从溶液中分离出来。经过水热合成法合成的Fe₃O₄/MnO₂磁性复合氧化物催化剂在活化过一硫酸盐（2KHSO₅·KHSO₄·K₂SO₄）产生硫酸根自由基（SO₄-）降解水中有机污染物表现出了优良的性能。把不同质量的磁性Fe₃O₄微球与线状的MnO₂负载到一起,合成三种Fe₃O₄:MnO₂质量比分别为1:3、2:3、1:1的Fe₃O₄/MnO₂催化剂,经过XRD、SEM和TEM表征,表明这两种金属氧化物负载到一起。对比不同Fe₃O₄:MnO₂质量比的Fe₃O₄/MnO₂磁性复合氧化物催化剂活化2KHSO₅·KHSO₄·K₂SO₄的活性,发现Fe₃O₄/MnO₂（2:3）催化剂催化活性最高。通过考察不同因素对Fe₃O₄/MnO₂（2:3）催化活性的影响得出,水中罗丹明B（Rh B）降解的最佳条件为10 mg/L Rh B、0.4 g/L Fe₃O₄/MnO₂催化剂、0.3 g/L 2KHSO₅·KHSO₄·K₂SO₄、pH=8。Fe₃O₄/MnO₂（2:3）磁性复合氧化物催化剂经过3次循环利用后,催化活性没有明显下降。SO₄-在降解水中Rh B起主要作用。      

Investigation on the cross sensitivity of NO2 sensors based on In2O3 thin films prepared by sol-gel and vacuum thermal evaporation

In₂O₃ thin films have been prepared from commercially available pure In₂O₃ powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500°C for 24 and 1 h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500°C the films’ microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In₂O_3−x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In₂O₃ (HVTE) and nearly stoichiometric In₂O_3−x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO₂ gas (0.7–7 ppm concentration range), at 250°C working temperature. At this temperature and 0.7 ppm NO₂ the calculated sensitivities (S=R_g/R_a) yield S=10 and S=7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In₂O₃ films to CO and CH₄. Negligible H₂O cross has resulted in the 40–80% relative humidity range, as well as to 1 ppm Cl₂ and 10 ppm NO. Only 1000 ppm C₂H₅OH has resulted to have a significant cross to the NO₂ response.     

M3O4(M=FeCoCrMnMg)高熵氧化物粉体的简易制备及超电容性能研究

高熵氧化物以其独特的结构和潜在的应用前景引起了越来越多的关注。本工作采用简单易行的固相反应法制备了M₃O₄(M=FeCoCrMnMg)高熵氧化物粉体, 采用不同手段对粉体进行表征, 并采用涂覆法制备了 M₃O₄/泡沫镍(M₃O₄/NF)复合电极, 研究其超电容性能。结果表明, 随着煅烧温度升高, Fe₂O₃(H)/Co₃O₄(S)/Cr₂O₃(E)和Mn₂O₃(B)相继固溶进入尖晶石主晶相晶格; 在900 ℃煅烧2 h所得M₃O₄粉体的平均粒径为0.69 μm, 具有单一尖晶石结构(面心立方, Fd-3m, a=0.8376 nm), 且Fe、Co、Cr、Mn和Mg五种元素在晶粒内均匀分布, 呈典型的高熵氧化物特征。此外, M₃O₄/NF复合电极在1 mol/L KOH的电解液中, 当电流密度为1 A·g^-1时, 其质量比电容达到193.7 F·g^-1, 可见M₃O₄高熵氧化物在超级电容器电极材料领域具有良好的应用前景。     

新型Co3O4和WC共沉积β-PbO2电极用于锌电解沉积及电化学性能研究

采用复合电沉积技术在Pb-0.3wt%Ag/α-PbO₂基体上合成了WC和Co₃O₄颗粒共沉积的β-PbO₂复合沉积层。沉积行为研究发现,WC颗粒先于Co₃O₄颗粒吸附于基体上,将WC颗粒与Co₃O₄颗粒共沉积是一种抑制当Co₃O₄颗粒单独共沉积于β-PbO₂沉积层时发生团聚情况的有效方法。电极性能研究发现,WC或Co₃O₄颗粒的共沉积均会提高复合阳极的析氧电催化活性,此外,WC颗粒还有助于提高复合阳极的显微硬度和在Zn电解沉积溶液中的耐腐蚀性能。Co₃O₄颗粒的共沉积不利于β-PbO₂相的生长,WC颗粒的共沉积对β-PbO₂相的生长影响不大,两种颗粒同时共沉积有助于抑制酸性镀液中α-PbO₂相的生长。      

Magnetic properties and texture of sputteredFe/Fe3O4 multilayer films

Polycrystalline Fe/Fe₃O₄ multilayers have been fabricated with varying Fe/Fe₃O₄ ratios, period (bilayer) thickness, number of periods, and deposition sequence. The films were deposited by RF magnetron sputtering. The coercivity was found to vary in a nonlinear fashion between that of Fe and Fe₃ O₄. For selected multilayer geometries, the coercivity can be increased beyond that of single-layer Fe and Fe₃O₄ films. The magnetic saturation was observed to follow a linear mixture rule. These results suggest that a multilayer approach is useful for designing magnetic thin films and may allow fabrication of new materials for recording media applications. A secondary result was the ability to obtain highly textured polycrystalline films of both Fe and Fe₃O₄ on amorphous substrates for selected multilayer geometries. The texture results, which may be generally applicable, suggest that relatively thin multilayers of only a few periods may provide a means to control polycrystalline film texture on amorphous substrates