Wood Pulp Fiber Wrapped by Fish-Scale Graphene as Flexible and Free-Standing Supercapacitor Electrode

Poplar wood pulp was adopted as both frame and precursor for the synthesis of pulp fiber (PF)/reduced graphene oxide composite via a simple and low-cost method. In this method, the PF based on graphene (PFG) composite film electrode was prepared by a simple vacuum filtration process with various ratios (PF: reduced graphene oxide (RGO)?=?5:1, PF:RGO?=?5:2, PF:RGO?=?5:3, PF:RGO?=?5:4, PF:RGO?=?5:5). In terms of special structures, the PFG can be used as electrodes without metal-collector, adhesives, and additives. The optimal ratio (PF:RGO?=?5:4) film electrode displayed a high areal-specific capacitance of 683 mF/cm² at 1?mA/cm² with a mass of 5.3?mg/cm² (specific capacitance of 129?F/g) and good cycling stability (87.5% capacitance retention after 10,000 cycles at 5?mA/cm²) as well as excellent rate capability and high flexibility (suitable for any angle, even 180°). Moreover, the device could possess a maximum energy density of 47.71?μWh/cm² and a maximum power density of 1251?μW/cm². These results suggest that the composite PGF film is a promising electrode material.     

葡萄柚皮多孔碳高性能对称性超级电容器电极材料的制备及性能

以柚子皮为碳源(GC),高温氧化碳化(GCO)处理后采用K₂CO₃活化制得GCO600,最佳优化产物GCO600-14具有丰富的网状孔隙,其比表面积达661.7 m²/g。三电极体系中,在1 A/g时,GCO600-14的比电容为413 F/g,电流密度扩大30倍后仍可达到2 896 F/g,为原先的70%;循环5 000圈后比电容仍未原来值的96%。构建的对称性电容器GCO600-14//GCO600-14能量密度为26、20.2 (W·h)/kg时,相应的功率密度分别为720、20 800 W/kg。说明GCO600-14作为新型的、环境友好的储能材料具有潜在的应用前景。     

Porous Carbon Spheres Derived from Hemicelluloses for Supercapacitor Application

With the increasing demand for dissolving pulp, large quantities of hemicelluloses were generated and abandoned. These hemicelluloses are very promising biomass resources for preparing carbon spheres. However, the pore structures of the carbon spheres obtained from biomass are usually poor, which extensively limits their utilization. Herein, the carbon microspheres derived from hemicelluloses were prepared using hydrothermal carbonization and further activated with different activators (KOH, K₂CO₃, Na₂CO₃, and ZnCl₂) to improve their electrochemical performance as supercapacitors. After activation, the specific surface areas of these carbon spheres were improved significantly, which were in the order of ZnCl₂ > K₂CO₃ > KOH > Na₂CO₃. The carbon spheres with high surface area of 2025 m²/g and remarkable pore volume of 1.07 cm³/g were achieved, as the carbon spheres were activated by ZnCl₂. The supercapacitor electrode fabricated from the ZnCl₂-activated carbon spheres demonstrated high specific capacitance of 218 F/g at 0.2 A/g in 6 M KOH in a three-electrode system. A symmetric supercapacitor was assembled in 2 M Li₂SO₄ electrolyte, and the carbon spheres activated by ZnCl₂ showed excellent electrochemical performance with high specific capacitance (137 F/g at 0.5 A/g), energy densities (15.4 Wh/kg), and good cyclic stability (95% capacitance retention over 2000 cycles).     

富氮多孔碳纤维的制备及其在超级电容器中的应用

以聚丙烯腈（PAN）为前驱体,制备具有发达三维网络结构的大/中孔PAN纤维,采用水合肼和盐酸羟胺处理使PAN纤维在产生交联反应的同时进一步引入氮原子,制备了富氮多孔碳纤维,并考察了富氮多孔碳纤维的形貌结构、孔结构特征及电化学性能。结果表明：富氮多孔碳纤维中的N和O原子含量分别为13.53%和8.01%,在电流密度为0.1 A/g时,比电容为222 F/g,比表面电容达0.80 F/m²。     

水热法制备Mn_3O_4/石墨烯复合材料及其电化学性能

采用水热法制备Mn3O4/石墨烯复合材料。石墨烯的含量对产物的形貌和结构有决定性的影响。当石墨烯与MnO2质量比1∶3时,制备得到MnOOH/石墨烯复合材料,当石墨烯与MnO2质量比1∶1时,制备得到Mn3O4/石墨烯复合材料。石墨烯与Mn3O4复合可使Mn3O4更大可能地释放赝电容,在电流密度2 A/g时,Mn3O4/石墨烯的比电容值为297.14 F/g。     

多孔碳纳米线/MnO_2复合材料的制备及其在电化学超级电容器中的应用研究

采用化学气相沉积法(CVD),以1,2-邻二氯苯和二茂铁为前驱体批量制备高纯度多孔碳纳米线(PCNF)。采用微波法将MnO2负载在多孔碳纳米线上从而构筑MnO2/PCNF复合材料。用SEM、TEM、XRD和TGA等测试手段对所得材料进行形貌及结构分析,采用循环伏安和恒流充放电测试检测MnO2/PCNF复合材料的电容特性。实验结果表明,该复合材料比电容较高,循环性能良好,在1000圈循环测试(2A·g-1)后电容保持率为89.3%。     

基于微喷技术的氧化石墨烯基层层自组装电极涂层

改变以传统浸涂法为基础的层层自组装成膜,进一步结合规模化、可控性和均匀性超声雾化微喷技术,在柔性聚酰亚胺基底表面成功制备以静电相互作用力为驱动力的氧化石墨烯基层层自组装(GO–NH2/GO–COOH)n电极涂层,进而通过加热还原处理获取(RGO–NH2/RGO–COOH)n,提升电极涂层导电性。结果表明,基于超声雾化微喷技术的层层自组装导电薄膜可被规模化均匀制备,且随着薄膜层数的增加导电性增强。另外,与浸涂法层层自组装成膜相比,在n=20时,还原后的薄膜方阻由(923.3±29.3)kΩ/sq明显降低至(227.7±12.1)kΩ/sq。因此,进一步改善还原条件后,其未来可被潜在应用于一系列柔性电子器件。     

纳米氧化铜/石墨烯修饰电极的制备及对H_2O_2的检测

采用电化学方法在玻碳电极上修饰石墨烯及纳米氧化铜,制备了纳米氧化铜/石墨烯修饰电极(nanoCuO/ERGO/GCE)。研究了纳米氧化铜/石墨烯修饰电极的电化学性质。该修饰电极在氢氧化钠溶液中,低电位下(0.08V)可催化氧化过氧化氢。在2.3×10-5~3.0×10-3mol/L和3.0×10-3~8.3×10-3mol/L浓度范围内,过氧化氢的响应电流与浓度呈良好的线性关系,线性相关系数分别为0.9943和0.9972,检测限为6.96×10-6mol/L(三倍噪音法)。     

介孔CoMn2O4/还原氧化石墨烯复合材料的制备及其超级电容性能

采用共沉淀法制备了CoMn₂O₄/还原氧化石墨烯(CoMn₂O₄/rGO)复合电极材料,并研究了石墨烯含量对CoMn₂O₄/rGO复合材料形貌、微观结构及电化学性能的影响。结果表明:CoMn₂O₄纳米颗粒沉积在石墨烯纳米片的表面,随着石墨烯含量的增加,CoMn₂O₄纳米颗粒在r GO表面的分布逐渐均匀,聚集现象消失。CoMn₂O₄/rGO具有高的比表面积及优良的电化学性能,其中CoMn₂O₄/rGO20 (rGO质量分数为20%)电容性能最好,在电流密度1 A/g时具有1 420 F/g的比电容。CoMn₂O₄/rGO30(rGO质量分数为30%)的倍率性能和循环稳定性能最好。2 000次充放电后,样品CoMn₂O₄/rGO30在5 A/g时的比电容保持率为94%,样品CoMn₂O₄的比电容保持率为78%。     

Porous Polyimide and Carbon Nanotubes: Solvent Vapor–Induced Transformation in the Nanochannels of Anodic Aluminum Oxide Templates

Polyimides (PIs) have attracted wide attention because of their exceptional thermal stability and applications in areas such as printed circuit boards and multichip modules. It remains a great challenge, however, to control the morphologies and properties of PI‐based nanomaterials, especially porous PI‐based nanotubes. In this work, a versatile method to fabricate porous PI nanotubes via the template method is developed, with a solvent vapor–induced transformation process. First, polyamic acid (PAA) solutions are used as precursors and infiltrated into the nanochannels of anodic aluminum oxide templates, forming PAA nanotubes. After the samples are annealed in tetrahydrofuran or dimethylformamide vapors, depression of the PAA tubes occurs, causing the formation of pores. The porous PAA nanotubes can be further converted to porous PI and carbon nanotubes by imidization and carbonization processes, respectively. The pore sizes of the porous nanomaterials can be controlled by changing the type of the annealing solvent and the solvent annealing time.     

Hybrid Carbon Supports Composed of Small Reduced Graphene Oxide and Carbon Nanotubes for Durable Oxygen Reduction Catalysts in Proton Exchange Membrane Fuel Cells

We demonstrated highly active and durable hybrid catalysts (HCs) composed of small reduced graphene oxide (srGO) and carbon nanotubes (CNTs) for use as oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells. Pt/srGO and Pt/CNTs were prepared by loading Pt nanoparticles onto srGO and CNTs using a polyol process, and HCs with different Pt/CNT and Pt/srGO ratios were prepared by mechanically mixing the two components. The prepared HCs consisted of Pt/CNTs well dispersed on Pt/srGO, with catalyst HC55, which was prepared using Pt/srGO and Pt/CNTs in a 5:5 ratio, exhibiting excellent oxygen reduction performance and high stability over 1000 cycles of the accelerated durability test (ADT). In particular, after 1000 cycles of the ADT, the normalized electrochemically active surface area of Pt/HC55 decreased by 11.9%, while those of Pt/srGO and Pt/C decreased by 21.2% and 57.6%, respectively. CNTs have strong corrosion resistance because there are fewer defect sites on the surface, and the addition of CNTs in rGO further improved the durability and the electrical conductivity of the catalyst. A detailed analysis of the structural and electrochemical properties of the synthesized catalysts suggested that the synergetic effects of the high specific surface area of srGO and the excellent electrical conductivity of CNTs were responsible for the enhanced efficiency and durability of the catalysts.     

Fabrication of Cellulose Nanofiber/Reduced Graphene Oxide/Nitrile Rubber Flexible Films Using Pickering Emulsion Technology for Electromagnetic Interference Shielding and Piezoresistive Sensor

With the rapid development of flexible electronics, the demand for flexible electromagnetic interference (EMI) shielding materials is increasing. This study develops a new green and effective strategy, consisting of graphene oxide (GO) and cellulose nanofibrils (CNF) co-stabilized Pickering emulsion combined with hot-pressing technology, to prepare flexible and conductive nitrile rubber (NBR) composite films. The composite films consist of a 3D network conductive skeleton structure of reduced GO (RGO) and an isolated NBR structure. This specific design results in a maximum high conductivity of 99 S m⁻¹, which is higher by an order of magnitude compared with that of the composites obtained using the traditional solution blending method, and a stable EMI shielding effectiveness of 25.81 dB in the X band. The introduction of the flexible NBR results in the excellent flexibility and structural strength of the composite film, and exhibits a decrease of 2.51% in the EMI shielding efficacy after 5000 cycles. As a piezoresistive sensor for wearable devices, the CNF-RGO/NBR flexible film can hold precise current signals and respond to finger motion. The findings of this study can provide new insights for the design of conductive and flexible composites as wearable and portable medical equipment and electronic devices.