NIWO4.docx

2.1. Synthesis of NiWO4 Nanostructure. All reagents were ofanalytical grade and directly used without any purification. NiWO4nanostructure was prepared via a simple coprecipitation method bymixing Na2WO42H2O and NiCl26H2O in a flask under mild stirring. Ina typical synthesis, 4.0 mmol of NiCl26H2O was dissolved in 50 mL ofdistilled water and stirred at 70 C for about 10 min. Then, 20 mL ofdistilled water containing 4.0 mmol of Na2WO42H2O was addeddropwise. The adding process was maintained for 30 min, and theresulting suspension was further stirred at 70 C for 3 h. Finally, theprecipitate was separated by centrifugation, rinsed with large amounts ofwater to remove the remaining reagents, and vacuum-dried at 60 C forfurther characterization. Similarly, a series of NiWO4 samples was alsoprepared at different reaction temperatures (25, 40, 55, and 85) anddenoted as NiW- x, where x represents the reaction temperatures.Furthermore, in order to increase the crystallinity of the as-preparedsamples, the obtained NiW-70 was subsequently calcined at 600 C for 1h and denoted as NiW-600.2.2. Material Characterizations. The morphology and microstructure of the samples were characterized by field-emission scanningelectron microscopy (FESEM, JSM-6701F, JEOL, Japan), transmissionelectron microscopy (TEM, JEM-2010, JEOL, Japan), Raman spectroscopy (Renishaw, In Via, UK, with 633 nm line of Ar ion laser as anexcitation source), N2 adsorption desorption isotherms (MicromeriticsASAP 2020 analyzer, USA), X-ray diffraction patterns (XRD, Rigaku D/MAX 2400 diffractometer, Japan) using Cu K radiation, = 1.5406 ,operating at 40 kV and 60 mAy, and X-ray photoelectron spectrometry(XPS, ESCALAB 210, VG Scientific, UK) using Mg K radiation undera pressure of 5 10 9 Torr.2.3. Electrochemical Measurements. Commercial AC (FujianXinsen Carbon Co. Ltd., China, with a specific surface area of 2000 m2g1) was used as received without further treatment. The workingelectrodes were prepared by pressing mixtures of the electroactivematerial, acetylene black, conducting graphite, and polytetrafluoro-ethylene (PTFE) binder (weight ratio of 80:7.5:7.5:5) onto a nickelfoam current collector. The electrochemical measurement of theindividual electrode was performed in a three-electrode system, in whichPt foil and Ag/AgCl electrodes were used as counter and referenceelectrodes, respectively. Each working electrode contained about 4.0 mgof electroactive material and had a geometric surface area of about 1 cm2.The asymmetric supercapacitor was assembled by separating the NiW-70 and AC electrodes with a separator (Figure 1) and performed in a Figure 1 . Schematic illustration of the assembled asymmetricsupercapacitor by using NiWO4 as cathode and AC as anode in aqueousKOH electrolyte.two-electrode system without the removal of oxygen from the solution.The loading mass ratio of active materials (NiW-70/AC) was estimatedto be 0.70 based on the cell voltage, and the specific capacitances werecalculated from galvanostatic discharging curves in a three-electrodesystem. Therefore, the weights of cathode and anode were calculated tobe 4.0 and 5.7 mg, respectively. Cyclic voltammetry (CV), galvanostaticcharge discharge, and electrochemical impedance spectroscopy (EIS)measurements were carried out in these three-electrode and two-electrode systems. EIS measurement was tested at the frequency rangeof 100 kHz to 10 mHz with an AC amplitude of 5 mV under an openF i g u r e 1 . Schematic illustration of the assembled asymmetricsupercapacitor by using NiWO4 as cathode and AC as anode in aqueousKOH electrolyte.ACS Applied Materials & Interfaces Research Article8045 /10.1021/am402127u | ACS Appl. Mater. Interfaces 2013, 5, 8044 8052circuit potential of 0.3 V. All of the above electrochemical measurementswere carried out on a CHI 660C (Shanghai, China) electrochemicalworkstation at room temperature by using 2 M KOH solution as theaqueous electrolyte. The cyclic stability of the electrode was alsoevaluated by a Land Battery Test System (Wuhan Kingnuo ElectronicCompany, CT2001A, China)NiWO4纳米结构的合成。所有试剂均为分析品位和直接使用没有任何净化。NiWO4纳米结构通过一个简单的共沉淀法制备混合Na2WO42水和NiCl26水在瓶在轻微的搅拌。在一个典型的合成、4.0中毒NiCl26水溶解在50毫升蒸馏水,搅拌在70C约10分钟。然后,20毫升蒸馏水包含4.0中毒Na2WO42水补充道一滴一滴地。添加过程维持30分钟,导致暂停进一步激起了在70C 3 h。最后,沉淀被离心分离,与大量的冲洗水,以消除剩余的试剂,vacuum-dried 60C进一步鉴定。同样,也是一系列NiWO4样品准备在不同反应温度(25岁,40岁,55岁和85年)此类- x,其中x表示的反应温度。此外,为了增加结晶度的准备样本,获得此类- 70随后煅烧在600C此类h和指示为- 600。2.3。电化学测量。商业交流(福建Xinsen碳有限公司、中国、与特定的表面面积2000平方米克1)作为接受没有进一步的治疗。工作电极制备按电活性的混合物材料、乙炔黑、导电石墨和polytetrafluoro-ethylene(PTFE)粘结剂(80:7.5:7.5:5的重量比)到镍泡沫电流收集器。的电化学测试单个电极在三电极体系中,执行中Pt箔和Ag / AgCl电极被用作计数器和参考电极,分别。每一个工作电极含有4.0毫克电活性材料和几何面积约1平方厘米。此类非对称超级电容器的组装是分离的70年和交流电极分隔符(图1),表现在图1。示意图说明组装的不对称超级电容器用NiWO4阴极和交流阳极在水KOH电解液。没有除氧二电极体系的解决方案。活动材料的装载质量比(此类- 70 / AC)估计0.70基于电池电压,具体各三电极恒电流放电曲线的计算系统。因此,阴极和阳极的权重计算分别是4.0和5.7毫克。循环伏安法(CV)、恒电流充电放电和电化学阻抗谱(EIS)在这些频率进行测量和二电极系统。EIS