免黏结剂V2O5和Fe2O3柔性电极的构建及在超级电容器中的应用

近年来,越来越多的研究致力于开发新型、超高能量密度、高法拉第反应活性的电极材料,尤其将其应用于新一代超级电容器储能系统。通过水热法直接在柔性基质碳布上生长海胆状V₂O₅纳米球和十四面体Fe₂O₃纳米盒子。V₂O₅微观结构和储能性能可通过改变水热时间进行调控。海胆状V₂O₅纳米球正极材料具有最高比容量535 F·g^-1。以十四面体Fe₂O₃纳米盒子作为负极材料组装的新型结构V₂O₅-CC//Fe₂O₃-CC柔性超级电容器,在功率密度为699.49 W·kg^-1时,能量密度可达46.06 W·h·kg^-1。而且具有良好的机械柔韧性,在180°弯曲循环测试5000次,比容量保持率仍高达83.4%。研究为开发下一代超高能量密度、柔性电子器件提供了一种通用而有效的策略。     

V2O5 nanosheets assembled on 3D carbon fiber felt as a free-standing electrode for flexible asymmetric supercapacitor with remarkable energy density

As an emerging energy storage device, supercapacitor is widely investigated owing to its excellent capability, quick charge-discharge and tremendous cycle life. The operation potential window, energy density and mass loading of supercapacitor must be taken into deep consideration for its practical application. In this work, an outstanding electrode based on CFF@V₂O₅ nanosheets was prepared. Then a free-standing asymmetric supercapacitor with CFF@V₂O₅ composite as positive electrode and CFF@AC as negative electrode was assembled. Owing to the functional groups produced on CFF after the activation, V₂O₅ nanosheets was immobilized. The composite exhibits remarkable specific capabilities of 1465 mF cm^?2 (492 F g^?1). The energy density of the assembled free-standing asymmetric supercapacitor achieves 0.928 mWh cm^?3 when the power density is 17.5 mW cm^?3. After 6000 charging-discharging cycles as under normal, bended and anti-bended conditions for respective 2000 cycles, the device retains 89.7% of the initial capacitance, exhibiting fascinating cycle stabilization. Finally, two devices linked series can lighten a LED of 1.8 V for 2 min after charging for 2.5 min, which is inspiring for the practical application and production of self-supporting asymmetric supercapacitors.     

纳米棒状氧化铁红的制备及表征

以尿素为沉淀剂,采用缓慢滴加方式,用均匀沉淀法制备了纳米棒状氧化铁红。考察了Fe^2＋浓度、反应时间、反应温度、尿素与Fe^2＋物质的量比等因素对产品粒径、形貌及收率的影响,并用TG,XRD,IR,UV-VIS,TEM等对样品进行了表征。确定了制备纳米棒状氧化铁红的最佳工艺条件：Fe^2＋浓度为0.50 mol/L,反应时间为180 min,反应温度为80℃,尿素与Fe^2＋物质的量比为20∶1,在此条件下制得前驱体,将前驱体在350℃下煅烧2 h,即可得到纳米棒状氧化铁红。样品的XRD,TEM表征结果为六方晶系的纳米棒状α-Fe2O3,其长轴约为300-500 nm,短轴约为20-40 nm,产品收率为75.90%,颜色为鲜红色,含质量分数5%样品的清漆对紫外线具有很好的吸收性能,而对可见光具有良好的透明性,其透光率在85%以上,可作为透明氧化铁红颜料使用。     

Sn对V2O5/Al2O3催化剂在异丁烷脱氢反应中的影响

以Al₂O₃为载体,采用等体积浸渍法制备了负载型高分散氧化钒催化剂（12%V₂O₅/Al₂O₃）,并选择Sn作为助剂对12%V₂O₅/Al₂O₃催化剂的表面性质进行调控,采用XRD、N₂等温吸脱附、NH₃-TPD、H₂-TPR、XPS、TEM和Raman光谱等方法对催化剂进行表征,结合活性评价实验,研究了催化剂表面物种分散状态、酸性和活性物种价态的变化与异丁烷脱氢活性和稳定性之间的关系。表征结果显示,Sn对V₂O₅/Al₂O₃表面的酸性和V物种在催化剂表面的分布和价态具有一定的调节作用,当Sn质量分数为1%时,氧化锡在催化剂表面分散均匀,对表面积和孔结构影响较小,同时,表面酸性变化较小,表面低价态的钒物种增多。活性评价结果表明,该催化剂在临氢反应条件下保持了最佳的脱氢活性及稳定性,异丁烷脱氢反应480min后,异丁烷转化率为46.8%,异丁烯收率为39.8%。     

Polyaniline grafted chitosan/GO-CNT/Fe3O4 nanocomposite as a superior electrode material for supercapacitor application

Developing appropriate stable electroactive electrode materials for supercapacitor application is the challenging issue, which attracts enormous attention in recent decades. In this regard, Fe₃O₄ nanoparticles are firstly synthesized on chitosan/graphene oxide-multiwall carbon nanotubes (CS/GM/Fe₃O₄). Then, polyaniline (PANI) is grafted on it via in situ chemical polymerization and named as CS/GM/Fe₃O₄/PANI. The as-prepared nanocomposites are characterized by Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. The capacitive properties of the electrodes are investigated in a three electrode configuration in 0.5 M Na₂SO₄ electrolyte by various electrochemical techniques. The specific capacitance of CS/GM/Fe₃O₄/PANI electrode is 1513.4 Fg⁻¹ at 4 Ag⁻¹ which is 1.9 times higher than that of CS/GM/Fe₃O₄ (800 Fg⁻¹). Meanwhile, the electrodes exhibit appropriate cycle life along with 99.8% and 93.95% specific capacitance at 100 Ag⁻¹ for chitosan/GO-CNT/Fe₃O₄ and polyaniline grafted chitosan/GO-CNT/Fe₃O₄, respectively.     

电化学沉积制备V2O5薄膜电极的表面结构及储钠性能

以含有CTAB的V₂O₅溶胶为电解液,采用电沉积法在不锈钢基体上沉积V₂O₅薄膜前体,经300℃烧结处理后制备了无黏结剂和导电剂的V₂O₅纳米薄膜电极。XRD测试表明该方法制备的V₂O₅薄膜是含水相的V₂O₅·nH₂O,与未添加CTAB制备的薄膜相比,其层间距明显变大。FESEM和AFM测试发现CTAB辅助电沉积制备的V₂O₅薄膜具有粗糙多孔的表面形貌;XPS测试表明CTAB辅助电沉积制备的V₂O₅薄膜中含有更多的低价钒离子（V⁴⁺）。电化学测试发现该方法制备的V₂O₅薄膜具有优异的嵌/脱Na⁺循环稳定性;与未添加CTAB制备的薄膜相比,CTAB辅助电沉积制备的V₂O₅薄膜具有更好的电化学反应可逆性、更强Na⁺扩散性能和更高的储钠比容量,是一种非常有应用前景的钠离子电池正极材料。     

花状与颗粒状NiMn2O4纳米材料的制备及其超级电容性能

分别以尿素和氨水为沉淀剂,采用热溶剂法制备了多孔的花状NiMn₂O₄和颗粒状NiMn₂O₄纳米电极材料,采用 X射线衍射仪、扫描电镜、透射电镜和N₂ 吸附-脱附等手段对NiMn₂O₄材料的物相、形貌结构和孔径分布进行了表征,并通过循环伏安、恒电流充放电、交流阻抗等方法测试了所制备材料的电化学性能。研究了沉淀剂对NiMn₂O₄材料形貌、微观结构及电化学性能的影响。结果表明：以尿素为沉淀剂的NiMn₂O₄是由纳米片组成的花状结构,纳米片厚度为50～60nm,比表面积为104m²/g。在 1A/g 电流密度下比电容为1614F/g,在5A/g电流密度下,尿素为沉淀剂的花状NiMn₂O₄材料经1000次恒电流充放电后其比电容可达初始值的89%。以氨水为沉淀剂的多孔NiMn₂O₄为直径约30nm的纳米颗粒结构,颗粒间团聚严重,比表面积为91m²/g。在1A/g电流密度下比电容为1147F/g,在5A/g电流密度下,氨水为沉淀剂的颗粒状NiMn₂O₄材料经1000次恒电流充放电后其比电容可达初始值的80%。尿素为沉淀剂的花状NiMn₂O₄具有优越的超级电容性能。     

硫源对双壳层NiCo2S4超级电容性能影响

通过自模板法,选用硫代乙酰胺（TAA）、硫脲（TU）分别作硫源制备双壳层NiCo₂S₄纳米材料。其中以TAA为硫源制备的NiCo₂S₄表现出高的比电容（2064F/g,当电流密度为0.5A/g时）,优异的倍率性能（1291F/g,当电流密度为20A/g时）和较好循环稳定性。由动力学机制分析可知,NiCo₂S₄-TAA表面控制电容和扩散控制电容较NiCo₂S₄-TU均有提升。通过实验分析可知,TAA作为硫源合成的NiCo₂S₄是由较小的次级颗粒聚集而成,这有利于电化学过程中电解质离子的扩散。由于较好的导电性能和离子扩散速率,NiCo₂S₄-TAA表现出优异的电化学性能。上述结果表明,在本实验条件下,TAA是制备NiCo₂S₄电容器电极材料的最佳硫源。     

V2O5复合薄膜材料的电子结构研究

采用自洽场离散为分Xα方法对纯V2O5及V2O5复合薄膜不同状态的O1s及V2p轨道电子结合能和键强度等进行了研究。结果表明,V2O5结构中存在4种状态的氧和3种状态的钒,聚合物（PEO）和聚合物（PEO）－Li^2 嵌入V2O5结构主要存在于层间的位置,与双键氧产生弱的键合作用,导致对双键氧与五价钒的含量降低,三键氧与三价、四价的含量增加;纯V2O5层间嵌入的Li^ 与周围氧的共价链与静电力都非常明显,V2O5层间引入PEO后再嵌入Li^ ,Li^ 与周围氧的共价键与静电力都变的非常微弱,说明PEO嵌入V2O5层间使Li^ 具有很好的注和／脱出可逆性。     

Photo-enhanced catalytic decomposition of isopropanol on V2O5

The effect of UV-visible photo irradiation has been investigated on the decomposition of isopropanol over V₂O₅. A 2.5-fold photo-enhancement in the rate of the dehydration (-H₂O) reaction was observed under UV-visible photo irradiation compared to thermal heating of the catalyst. The increase in propene yield under photo irradiation is believed to be initiated from photo excitation (photo-reduction) of the V₂O₅ complex to [-V⁴⁺-O^–] * thus, increasing surface concentration of V⁴⁺ species. The V⁴⁺ active surface species is assumed to serve as the center for adsorption of isopropanol. The observed increase in water formation along with the formation of propene suggests that the rate determining step for the dehydration reaction is desorption of water. Selectivity toward the dehydrogenation (-H₂) reaction has also been measured to be 1% under UV-visible photo irradiation as compared to 15% under thermal heating of the catalyst.     

V2O5/AC催化剂吸附NH3及其选择性还原脱硝活性

在不同活性焦(Activated Coke, AC)载体上以等体积浸渍法负载V2O5,制备出一系列V2O5/AC催化剂. 通过NH3暂态响应实验和NH3穿透时间实验考察了在200℃下V2O5/AC的表面积、灰分、表面官能团和V2O5对NH3的吸附量及NO的选择性催化还原活性的影响. 结果表明,对于载体未经硝酸处理的催化剂,NH3的吸附位主要是V2O5(参与脱硝反应的NH3的吸附量与催化剂上V2O5负载量的比值为1:5),活性焦及其中的灰分对NH3的吸附量很小;硝酸处理在活性焦表面引入的含氧和含氮酸性官能团对参与脱硝反应的NH3的吸附量是V2O5上吸附量的1.3倍,这些官能团不影响V2O5对NH3的吸附;活性焦上吸附的NH3的脱硝活性很低,但可迁移至V2O5上参与脱硝.     

Catalytic decomposition of ethanol on ­V2O5/AlPO4 catalysts

Different ratios of vanadium pentoxide supported on aluminum phosphate (1–30 mol%) have been prepared by an impregnation method. The original and calcined samples were characterized by TG, DTG, DSC, X‐ray diffraction, IR spectra, N₂ adsorption and electrical conductivity measurements. The catalytic decomposition of ethanol has been carried out at 210 °C in a flow system at 1 atm using air as a carrier gas. The results indicate that the catalysts calcined at 400 °C were active and selective towards ethene formation whereas the samples calcined at 600 °C showed a drastic reduction in both activity and selectivity. © 2000 Society of Chemical Industry     

纳米锰氧化物超级电容器电极材料的制备与性能

采用模板和液相沉淀两种方法制备了锰的氧化物,XRD的测试结果表明,两种方法制备的锰氧化物分别为MnO2和Mn3O4。从TEM图可以看出,模板法制备的MnO2为直径为5~8nm左右的颗粒,而用液相沉淀制备的Mn3O4形貌为直径约为10nm左右的纤维棒。循环伏安和充放电测试结果都表明MnO2是更好的超电容器的电极材料。MnO2和Mn3O4在200mA·g-1电流密度下的放电比电容分别为157.5和145.0F·g-1,经过500次充放电后比电容分别为132.5和125.0F·g-1,充放电效率分别为64.9%和63.7%。     

NiMn2O4/还原氧化石墨烯复合材料的制备及其超级电容性能

采用水热法制备了NiMn₂O₄/还原氧化石墨烯（NiMn₂O₄/rGO）复合电极材料,研究了石墨烯对NiMn₂O₄/rGO材料形貌、微观结构及电化学性能的影响。结果表明：NiMn₂O₄纳米片沉积在石墨烯片的表面,聚集现象消失。与纯NiMn₂O₄相比,NiMn₂O₄/rGO具有高的比表面积和优良的电化学性能。在1A/g时具有1375F/g的比电容,而纯NiMn₂O₄的比电容为924F/g。5000次充放电后,NiMn₂O₄/rGO在5A/g时的比电容保留率为90%,而NiMn₂O₄的比电容保留率为78%。NiMn₂O₄/rGO表现出良好的电容性能,作为超级电容器电极材料具有广泛的应用前景。     

制备参数对纳米V2O5颗粒形貌的影响

用透射电子显微镜、微观体视学图象分析系统研究冶金V2O5溶胶中V2O5颗粒的微观形貌,以及制备工艺参数对其微观形貌的影响。结果表明;V2O5颗粒形貌呈现出多样性,既有针状,又有近球状和球状,还有“短棒状”和“椭球状”;近球状V2O5颗粒非常接近于球状;V2O5颗粒的团聚方式也呈现多样性,且团聚时效较快。随着水的体积与冶金五氧化二钒质量之比[简称水钒比,V(w)／m(V)]的降低,V2O5颗粒形状由针状、近球状逐渐过渡到球状。当V(w)／m(V)在40mL／g以下时,颗粒基本上呈球状。熔化温度升高,则V2O5颗粒直径增大。恒温时间延长则V2O5颗粒直径减小。     

絮凝氧化铁悬浮液流变性质研究

应用LVDV-Ⅲ+型可编程流变仪测定了微米级氧化铁悬浮液絮凝处理后的流变特性,考察因素包括悬浮液固相质量浓度、pH值、絮凝剂添加量、搅拌速度。结果表明,悬浮液浓度不同,其流变性能也表现出不同,在相同剪切速率下,高质量分数悬浮液的表观粘度和剪切应力都大于低质量分数悬浮液的表观粘度和剪切应力;pH对絮凝悬浮液流变性有重要的影响。絮凝悬浮液粘度随pH的增加先增大后减小,絮凝剂聚合氯化铝添加量为80 mg的条件下,pH=6.14时表观粘度最大;絮凝剂浓度的不同,对于悬浮液流变性能的影响也不同,在相同剪切速率下,添加高浓度絮凝剂悬浮液的表观粘度和剪切应力都大于添加低浓度絮凝剂悬浮液的表观粘度和剪切应力,增加絮凝剂浓度对提高悬浮液粘着性能具有积极意义;对悬浮液搅拌强度不同其流变性能也表现出不同,在相同剪切速率下,悬浮液的表观粘度和剪切应力随着测试前对它搅拌强度的增加表现出先增大后减小。     

A molecular mechanics study of the adsorption of ethane and propane on V2O5(001) surfaces with oxygen vacancies

Adsorption geometries and energies of ethane and propane physisorbed on the (001) surface of vanadium pentoxide with oxygen vacancies were determined by a molecular mechanics simulation. Three types of oxygen vacancies, built up by removal of vanadyl oxygen, two-fold and three-fold coordinated oxygen, respectively, have been modeled as defects. The energetically most favorable adsorption site is on top of a vacancy of two-fold coordinated oxygen for ethane and propane, respectively. The next favorable site for both alkanes is on top of a vacancy of vanadyl oxygen. Due to the generation of a “van der Waals cage” which traps the hydrocarbon the adsorption on the defect site is favored in comparison with the ideal surface for these two defect types. A vacancy of three-fold coordinated oxygen does not lead to an enhancement of adsorption and pushes the reactant towards the unperturbed surface areas due to the fact, that no energy minimum can be obtained in the vicinity of the defect. This revised version was published online in August 2006 with corrections to the Cover Date.     

超声波一直接沉淀法制备超细氧化铁

将超声波用于以硫酸亚铁铵、草酸为原料的直接沉淀法制备超细氧化铁。对氧化铁的前驱体——草酸亚铁的合成及焙烧工艺进行了详细研究。讨论了反应温度、物料浓度、超声沉淀反应时间以及焙烧温度、焙烧时间对氧化铁粒度的影响。结果发现，在一定的试验条件下，可获得粒度小于40nm的氧化铁。XRD实验表明，所合成的Fe2O3为α型，TEM的测试结果平均粒径为20nm，且分散性好。     

一步法合成二维Ti3C2及其电化学性能研究

二维过渡金属碳/氮化物（MXene）是一种新型二维材料,可通过从MAX相前体中选择性刻蚀 A 原子层获得。在传统制备MXene的方法中,常用的刻蚀剂是氢氟酸。然而高浓度氢氟酸的使用,不可避免会带来安全问题,甚至破坏MXene的晶体结构,从而限制本征物理化学性能。从典型的碳化物前体Ti₃AlC₂出发,使用 NH₄BF₄作为刻蚀剂,有效降低体系中酸的使用量;在反应过程中,刻蚀 A 层的同时,\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}进入堆垛层间,扩大层间距,弱化层间作用力。因此,仅通过简单手摇就可以实现高效剥离,得到具有完整晶体结构的二维Ti₃C₂。进一步测试了Ti₃C₂的电化学性能,结果显示,所得的Ti₃C₂具有优异的性能（扫描速率为5 mV?s^-1时为503 F?g^-1）和循环稳定性（在5 A?g^-1下循环10⁴次后电容保持率为95.8%）。本文为Ti₃C₂纳米片的合成及应用提供了新的思路。     

Reactivity of the V2O5–TiO2-anatase catalyst: role of the oxygen sites

A theoretical DFT-based study combining cluster and periodic models has been performed to elucidate the role of the oxygen sites in the reactivity of the vanadia/titania catalyst. We have focused on the coordination of the oxygen sites that has been directly related to reactivity. First, the reactivity of the active phase vanadia is studied by means of a V₂O₅ cluster model. The support TiO₂-anatase is then modeled by periodic conditions. Finally, a complex model containing vanadia units dispersed on anatase surfaces (100) and (001) is explored. According to our results, reactivity of the catalyst is associated to the presence of V–O–Ti bonds, the vanadyl V = O bonds being too stable to react.