A novel chemical synthesis and characterization of Mn3O4 thin films for supercapacitor application

Mn₃O₄ thin films have been prepared by novel chemical successive ionic layer adsorption and reaction (SILAR) method. Further these films were characterized for their structural, morphological and optical properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), field emission scanning electron microscopy (FESEM), wettability test and optical absorption studies. The XRD pattern showed that the Mn₃O₄ films exhibit tetragonal hausmannite structure. Formation of manganese oxide compound was confirmed from FTIR studies. The optical absorption showed existence of direct optical band gap of energy 2.30 eV. Mn₃O₄ film surface showed hydrophilic nature with water contact angle of 55°. The supercapacitive properties of Mn₃O₄ thin film investigated in 1 M Na₂SO₄ electrolyte showed maximum supercapacitance of 314 F g⁻¹ at scan rate 5 mV s⁻¹.     

掺杂离子对聚吡咯膜的电化学容量性能的影响

用电化学方法制备了分别以对甲基苯磺酸根(TOS-), 高氯酸根(ClO-4)和氯离子(Cl-)掺杂的聚吡咯(PPy)膜. 用循环伏安(CV)、恒电流充放电和电化学阻抗谱(EIS)等测试了它们的电化学容量性能. 用扫描电镜(SEM)和X射线衍射(XRD)分别研究了这三种PPy膜的形貌和结构. 研究发现, 由于具有疏松多孔的形貌和更有序的分子链结构, PPy-TOS和 PPy-Cl膜具有较好的充放电能力, 在深度充放电时仍具有很小的电化学电阻, 其离子扩散接近理想电容器的离子扩散机理. PPy-Cl(聚合电量2 mAh·cm-2)的比容量在扫描速率为5 mV·s-1时高达270 F·g-1, 扫描速率200 mV·s-1时仍高达175 F·g-1, 特别是, 其比能量高达35.3 mWh·g-1. PPy-TOS由于有质量较大的掺杂离子(TOS-)因而比容量略低(146 F·g-1, 扫描速率5 mV·s-1), 但具有超快速充放电能力, 在扫描速率为200 mV·s-1时, 比容量为123.6 F·g-1, 其比功率高达10 W·g-1. 并且, 两种电极材料均具有稳定的电化学循环性能.     

“Dissolution-reassembly” for N-doped hollow micro/meso-carbon spheres with high supercapacitor performance

N-Doped hollow carbon spheres with mesoporous/microporous shells and outstanding performance in supercapacitor has been prepared by “dissolution-reassembly” method.     

Design and green synthesis of 1-(4-ferrocenylbutyl)piperazine chemically grafted reduced graphene oxide for supercapacitor application

In this paper, we report the green synthesis of 1-(4-ferrocenylbutyl)piperazine chemically grafted rGO (P.Fc/rGO) as a battery-type supercapacitor electrode material. For this purpose, initially, the ability of the aqueous Damson fruit extract is investigated in the reduction reaction of graphene oxide (GO). 1-(4-ferrocenylbutyl)piperazine (P.Fc) is synthesized via nucleophilic substitution reaction of piperazine with as-synthesized 4-chlorobutylferrocene. In continue, P. Fc is incorporated to GO by ring-opening reaction of epoxide groups on the GO surface. In the next step, the modified reduction method by aqueous Damson fruit extract was used to prepare the P.Fc/rGO from P.Fc/GO. The prepared materials were characterized by various techniques including FT-IR, Uv–vis, XRD, SEM, EDX, and BET. N₂ adsorption–desorption data of P.Fc/rGO nanocomposite shows that the surface area is 37.746 m² g⁻¹. The capability of P.Fc/rGO nanocomposite for using as an energy storage electrode material in battery-type supercapacitor was examined by investigation of its electrochemical behavior by CV, EIS, and GCD measurements. The charge storage capacity of 1,102 mAh g⁻¹ is achieved at 2.5 A g⁻¹. This nanocomposite shows 89% retention of charge storage capacity after 2000 CV cycles.     

Analysis of graphene-like activated carbon derived from rice straw for application in supercapacitor

Activated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. A very slack activated carbon with ultra-thin two-dimensional (2D) layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures.     

Longitudinal unzipping of carbon nanotubes and their electrochemical performance in supercapacitors

The capacitive properties of graphene nanoribbons (GNRs) with different reduction levels were investigated. GNRs have been synthesized through thermal reduction of oxidized GNRs in the temperature range 100–400 °C. Oxidized GNRs were synthesized by longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) by means of chemical treatments. Scanning electron microscopy and transmission electron microscopy observations showed, that the efficient tube unzipping yielded improved effective surface area without any tube annihilation by the unzipping process of MWCNTs. Electrochemical studies indicated that through unzipping of MWCNTs, specific capacitance increased from 8 to 28 F g⁻¹ at discharge current density of 0.5 A g⁻¹, confirming increased active surface area and increased defect density in the MWCNTs surface. Unzipping of MWCNTs resulted in decreased rate capability of the electrode because of low electrical conductivity due to oxidization during the unzipping process. Thermal reduction of unzipped sample affected both specific capacitance and rate capability of electrodes. The highest specific capacitance of 62 F g⁻¹ at discharge current density of 0.5 A g⁻¹ was obtained for the sample unzipped and thermally annealed at about 150 °C. The amount of oxygen-containing groups was shown to be an important factor influencing the performance of the GNRs. These results make unzipped MWCNTs promising electrode materials for supercapacitor applications.     

Bamboo-based activated carbon for supercapacitor applications

Bamboo-based activated carbon is synthesized by a simple heat treatment with or without KOH activation, and characterized for possible energy storage applications. The KOH activation introduces a very large surface area of more than 3000 m² g⁻¹ to the bamboo-based activated carbon, resulting in high specific capacitance, energy density, and power density in an aqueous electrolyte. The specific capacitance retention is more than 91% of the original capacitance after 3000 cycles, proving excellent cyclic stability for supercapacitor applications. Our results indicate that the natural resource of common bamboo could be an essential raw material for the energy storage devices.     

氧化钌/石墨纳米片复合阵列电极的制备及其电容性能

通过电化学剥离法在石墨棒表面构筑了层数不等、彼此平行且垂直于基底的二维石墨纳米片(GNS)阵列, 而后采用阴极还原电沉积法在GNSs 表面均匀地包覆了一层氧化钌(RuO₂·xH₂O)薄膜, 形成了RuO₂·xH₂O/GNS 复合阵列电极. 电化学测试表明, RuO₂·xH₂O/GNS 复合阵列电极具有优良的超电容性能, 在0.5mol·L^-1 H₂SO₄电解质溶液中, 扫描速率为5 mV·s^-1, 电位窗口为0.9 V时, 其比电容高达4226 F·m^-2, 并且具有优异的循环性能, 经过20000圈充放电循环后, 电容保持率高达94.18%.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体,水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂）,制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM）,透射电镜（TEM）,X射线衍射（XRD）,热重分析（TGA）对其结构进行表征;采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面,形成多层次结构,并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构;MnO₂纳米片具有典型的K-Birnessite 型晶体结构;复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1;随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极,活性炭（AC）为负极,1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器,发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V,容量可达86F·g^-1,且表现出良好的电容特性和大电流放电性能.     

水热合成部分还原氧化石墨烯-K2Mn4O8超级电容器纳米复合材料

通过控制水热反应温度以及氧化石墨烯(GO)与高锰酸钾的填料比, 合成了两组部分还原的GO-K₂Mn₄O₈纳米复合材料. X射线衍射(XRD)分析说明水热过程中合成了α-MnO₂和一种新的晶相K₂Mn₄O₈.通过X射线光电子能谱(XPS)分析了水热反应前后氧化石墨的含氧官能团的变化. 扫描电子显微镜(SEM)显示样品由片状还原的氧化石墨烯构成, 其表面附有许多小的纳米颗粒, 这种结构有利于储能时电子的传递. 通过这两组复合材料的结构分析, 更好地理解了材料的电化学性能的变化. 利用循环伏安法和恒流充放电测试比较了材料的电容性能. 用1 mol·L^-1的硫酸钠做电解液, 电位范围是0-1 V, 在1 A·g^-1的电流密度下, 测得的样品最佳比电容达到251 F·g^-1, 能量密度为32 Wh·kg^-1, 功率密度为18.2 kW·kg^-1. 并且在5 A·g^-1的电流密度下循环1000次后样品的比电容仍维持在初始比电容的88%.