ZnCo2O4及ZnCo2O4/rGO复合材料的制备与电化学性能

采用一步水热法制备尖晶石型钴酸锌(ZnCo_2O_4)及钴酸锌/石墨烯(ZnCo_2O_4/rGO)复合材料,通过XRD,SEM和RST5000电化学工作站对材料的组分、表面形貌及电化学性能进行表征。通过改变水热温度,制备出具有辐射状花簇团结构、褶皱片层结构和表面光滑的球体结构的ZnCo_2O_4电极材料。结果表明:加入石墨烯后,ZnCo_2O_4呈规则的多边形结构,附着在石墨烯片上,两者的协同作用可有效改善电极材料的电化学性能;钴酸锌与氧化石墨烯的质量比为6∶1时得到的ZnCo_2O_4/rGO复合材料的比电容为205F/g,比纯ZnCo_2O_4的比电容提升了约114%。     

3D Printed Mechanically Robust Graphene/CNT Electrodes for Highly Efficient Overall Water Splitting

3D printing of graphene electrodes with high mechanical strength has been a growing interest in the development of advanced energy, environment, and electronic systems, yet is extremely challenging. Herein, a 3D printed bioinspired electrode of graphene reinforced with 1D carbon nanotubes (CNTs) (3DP GC) with both high flexural strength and hierarchical porous structure is reported via a 3D printing strategy. Mechanics modeling reveals the critical role of the 1D CNTs in the enhanced flexural strength by increasing the friction and adhesion between the 2D graphene nanosheets. The 3DP GC electrodes hold distinct advantages: i) an intrinsically high flexural strength that enables their large-scale applications; and ii) a hierarchical porous structure that offers large surface area and interconnected channels, endowing fast mass and/or charge and ions transport rate, which is thus beneficial for acting as an ideal catalyst carrier. The 3DP GC electrode integrated with a NiFeP nanosheets array exhibits a voltage of 1.58 V at 30 mA cm⁻² as bifunctional electrode for water splitting, which is much better than most of the reported Ni-, Co-, and Fe-based bifunctional electrocatalysts. Importantly, this study paves the way for the practical applications of 3D printed graphene electrodes in many energy conversion/storage, environmental, and electronic systems where high flexural strength is preferred.     

A facile approach to the synthesis of graphene nanosheets under ultra-low exfoliation temperature

High specific surface area graphene nanosheets have been obtained from graphite oxide by using an effective modified exfoliation method under vacuum, the exfoliation temperature (135 degrees C) is much lower than that conventionally applied (1050 degrees C) to obtain monolayer graphene sheets via rapid thermal shock. These products have fluffy and highly porous structure and with a lateral size typically of a few micrometers. Transmission electron microscopy (TEM) observation shows that it looks like a wrinkled transparent ultrathin film consisting of single or few-layer graphene sheets, and their Brunauer-Emmett-Teller surface area is as large as 750 m2/g. Simultaneously, X-ray photoelectron spectroscopy analysis revealed that considerable amount of oxygen-containing groups (C/O ratio, 5:1) retained on the graphene sheets after exfoliation process, which would provide convenience for further modification of the surface properties and chemistry of graphene sheets. This work offers a facile and scalable approach to fabricate graphene oxide and opens up a new vista of various potential applications electronics and composite materials.     

Oriented Arrangement: The Origin of Versatility for Porous Graphene Materials

Macroscopic porous graphene materials composed of graphene sheets have demonstrated their advantageous aspects in diverse application areas. It is essential to maximize their excellent performances by rationally controlling the sheet arrangement and pore structure. Bulk porous graphene materials with oriented pore structure and arrangement of graphene sheets are prepared by marrying electrolyte‐assisted self‐assembly and shear‐force‐induced alignment of graphene oxide sheets, and the super elasticity and anisotropic mechanical, electrical, and thermal properties induced by this unique structure are systematically investigated. Its application in pressure sensing exhibits ultrahigh sensitivity of 313.23 kPa^?1 for detecting ultralow pressure variation below 0.5 kPa, and it shows high retention rate for continuously intercepting dye molecules with a high flux of ≈18.7 L m^?2 h^?1 bar^?1 and a dynamic removal rate of 510 mg m^?2 h^?1.     

Preparation of a Cu<Subscript>2</Subscript>O/rGO porous composite through a double-sacrificial-template method for non-enzymatic glucose detection

We report a double-sacrificial-template method for the fabrication of a Cu₂O and a reduced graphene oxide (rGO) porous nanocomposite (Cu₂O/rGO), which has great potential in non-enzymatic glucose detection. Firstly, an aqueous graphene oxide (GO) solution was dispersed in a polystyrene (PS)/cyclohexane (CH) solution to prepare a water-in-oil emulsion at 50 °C. Then, the emulsion was cast onto a glass substrate to evaporate solvents and cooled down to room temperature. During that time, the self-assembly of the GO sheets and the PS chains takes place at the interface. The cooling of the emulsion below the θ temperature of the system PS/CH (34.5 °C) facilitates the precipitation of the PS chains at the interface to form microcapsules. A sponge-like PS/GO composite film was thus obtained after complete evaporation of solvents, where the water droplets in the emulsion served as the first sacrificial template. The PS/GO composite was loaded with copper compounds and was then carbonized to remove the second template of the polymer. In this manner, a free-standing porous nanocomposite of Cu₂O/rGO was fabricated, and its structure was carefully characterized. The composite was applied as the working electrode in order to take advantages of its porous microstructure, the conductivity of rGO, and the electrochemical performance of crystalline nano-Cu₂O. The electrochemical responses of the composite to glucose were evaluated at glucose concentration ranging from 20 to 1000 μM. The results evidence that the porous nanocomposite of Cu₂O/rGO exhibits fast and linear amperometric responses to glucose with excellent sensitivities. Moreover, the stability of the Cu₂O/rGO composite in the electrolyte solution and its selective response to glucose have been demonstrated to indicate its practical potential.     

Flexible,Stretchable, and Transparent Planar Microsupercapacitors Based on 3D Porous Laser‐Induced Graphene

The graphene with 3D porous network structure is directly laser‐induced on polyimide sheets at room temperature in ambient environment by an inexpensive and one‐step method, then transferred to silicon rubber substrate to obtain highly stretchable, transparent, and flexible electrode of the all‐solid‐state planar microsupercapacitors. The electrochemical capacitance properties of the graphene electrodes are further enhanced by nitrogen doping and with conductive poly(3,4‐ethylenedioxythiophene) coating. With excellent flexibility, stretchability, and capacitance properties, the planar microsupercapacitors present a great potential in fashionable and comfortable designs for wearable electronics.     

三维石墨烯-碳纳米管复合材料的制备及其氧还原催化性能研究

采用化学气相沉积法（CVD）制备了硼、氮共掺杂三维石墨烯与碳纳米管复合的非金属电催化材料（B-N-G-CNT）。利用扫描电子显微镜（SEM）、能谱仪（EDS）、透射电子显微镜（TEM）对B-N-G-CNT的形貌、结构及成分进行了表征,结果显示：三维石墨烯－碳纳米管呈有序多孔网状结构,石墨烯与碳纳米管形成稳定的化学结合,具有质量高、缺陷少等优点。运用循环伏安法（CV）、旋转圆盘电极（RDE）、电流时间曲线（i-t curve）等手段测试了B-N-G-CNT在碱性介质中的氧还原电化学性能,结果表明：在浓度为0.1 mol·L-1 的KOH溶液中,B-N-G-CNT复合材料具有比 B-N-G更高的起始电位和半波势能,其电子转移数接近4电子;同时B-N-G-CNT比商业Pt/C具有更高的稳定性。     

3D composites of ZnSnO<Subscript>3</Subscript> nanoplates/reduced graphene oxide aerogels as an advanced lithium-ion battery anode

Zinc-based bimetal oxides have received considerable attention as anode for lithium-ion batteries (LIBs). A one-pot self-assembly hydrothermal method is developed for the fabrication of 3D hierarchical structure aerogels from zinc stannate (ZnSnO₃) and reduced graphene oxide (rGO). 3D interconnected porous structure with ZnSnO₃ hexagon nanoplates uniformly dispersed on graphene sheets has been constructed successfully, in which the crystalline hexagon nanoplates ZnSnO₃ are firstly used to prepare ZnSnO₃-based anode materials for LIBs. The as-prepared ZnSnO₃ nanoplates/reduced graphene oxide aerogels (ZnSnO₃–rGAs) electrode demonstrates an excellent reversible capacity (780 mAh g^?1) after 200 cycles at a certain current density (100 mA g^?1) and still delivers a specific capacity of 460 mAh g^?1 even at 1000 mA g^?1. The superior performance of lithium storage is attributed to the 3D porous hierarchical structure and the synergistic effects of uniform hexagon nanoplates ZnSnO₃ and rGO sheets.     

Graphene enhances Li storage capacity of porous single-crystalline silicon nanowires

We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO3 etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g(-1) that is much higher than the 1256 mAh g(-1) of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphene with the porous Si 1D nanostructure.     

磁性多孔RGO@Ni复合材料的制备和吸波性能

以氧化石墨烯和乙酰丙酮镍为原料,用溶剂热法合成了三维多孔RGO@Ni纳米复合材料。采用X射线衍射(XRD)和X射线光电子能谱(XPS)表征了材料的晶体结构和组成,根据拉曼谱分析了材料内部的石墨化程度和结构缺陷,用扫描电镜(SEM)和透射电镜(TEM)观察了材料的形貌和微观结构。结果表明,当RGO@Ni纳米复合材料的填充量(质量分数)为25%时在最小反射损耗(RL_min)和最大有效吸收带宽(EAB)方面显示出优异的EMW吸收性能;厚度为2.2 mm的RGO@Ni纳米复合材料其RL_min为-61.2 dB,而在2.5 mm匹配厚度下覆盖的EAB范围最广,为6.6 GHz(10.5~17.1 GHz)。这种复合材料优异的微波吸收性能,归因于协同效应的增强和特殊的多孔结构。     

Few layers of graphene as transparent electrode from botanical derivative camphor

Here, we report synthesis of large area graphene sheets by control pyrolysis of solid botanical derivative camphor (C₁₀H₁₆O) and fabrication of transparent electrodes. Raman study shows highly ordered graphene sheet with minimum defects. Second order Raman spectrum shows that graphene layers are more than single layer and can be controlled with amount of camphor pyrolyzed. Transmission electron microscopic images show presence of 4 layers for thinner and 13 layers for thicker graphene sheets. Transferred graphene sheets on glass substrates show very good transparency in wide range of wavelength (0.3-2 μm). Electrical measurements of the graphene sheets show thickness dependent sheet resistance. A sheet resistance of 203 Ω/sq is obtained at a transmittance of 63.5% of the graphene sheet. The technique to fabricate few layer of graphene as transparent electrode from camphor is both viable and scalable for potential large area optoelectronic applications.     

Freestanding Lamellar Porous Carbon Stacks for Low‐Temperature‐Foldable Supercapacitors

High‐performance supercapacitors (SCs) are important energy storage components for emerging wearable electronics. Rendering low‐temperature foldability to SCs is critically important when wearable devices are used in a cold environment. However, currently reported foldable SCs do not have a stable electrochemical performance at subzero temperatures, while those that are performing are not foldable. Herein, a freestanding pure‐carbon‐based porous electrode, namely, lamellar porous carbon stack (LPCS), is reported, which enables stable low‐temperature‐foldable SCs. The LPCS, which is fabricated with a simple vacuum filtration of a mixture of carbon fibers (CFs), holey reduced graphene oxides (HRGOs), and carbon nanotubes (CNTs), possesses a lamellar stacking of porous carbon thin sheets, in which the CFs act as the skeleton and the HRGOs and CNTs act as binders. The unique structure leads to excellent compression resilience, high foldability, and high electronic and ionic conductivity. SCs made with the LPCS electrodes and ionic liquid electrolyte show a high energy density (2.1 mWh cm^?2 at 2 mA cm^?2), low‐temperature long lifetime (95% capacity after 10 000 cycles at ?30 °C), and excellent low‐temperature foldability (86% capacity after 1000 folding cycles at ?30 °C).     

锂离子电池硅/碳纳米管/石墨烯自支撑负极材料研究

通过真空驱动自组装法及蒸汽处理得到结构疏松的硅/碳纳米管/石墨烯自支撑负极材料(Si/CNTs/GP)。纳米硅颗粒(50 nm)为活性物质, 均匀分布在石墨烯片层结构中间; 石墨烯作为碳基体, 通过自组装构筑形成二维导电网络; 碳纳米管(CNTs)具有超高导电性和良好的力学强度, 它通过吸附作用均匀分布在石墨烯基体上形成导电的支撑网络结构。经过蒸汽处理后, 石墨烯层间距明显增大, 层与层之间不再是紧密堆叠的结构, 而是形成一种疏松、褶皱、内部空隙丰富的片层结构。Si/CNTs/GP负极材料中丰富的内部空穴和贯穿孔洞, 提供了材料很高的比表面积, 能有效提高电解液对材料的浸润性, 极大缩短了离子传输距离。同时这些内部空穴也有效缓冲硅充放电时的体积膨胀, 提高了材料的结构稳定性和电化学性能。该负极材料在4 A/g的大电流密度下容量维持在600 mAh/g, 表现出良好的大电流循环稳定性能。     

Porous Hybrid Network of Graphene and Metal Oxide Nanosheets as Useful Matrix for Improving the Electrode Performance of Layered Double Hydroxides

Mesoporous hybrid network of reduced graphene oxide (rG‐O) and layered MnO₂ nanosheets could act as an efficient immobilization matrix for improving the electrochemical activity of layered double hydroxide (LDH). The control of MnO₂/rG‐O ratio is crucial in optimizing the porous structure and electrical conductivity of the resulting hybrid structure. The immobilization of Co‐Al‐LDH on hybrid MnO₂/rG‐O network is more effective in enhancing its electrode activity compared with that of on pure rG‐O network. The Co‐Al‐LDH?rG‐O?MnO₂ nanohybrid deliveres a greater specific capacitance than does MnO₂‐free Co‐Al‐LDH?rG‐O nanohybrid. The beneficial effect of MnO₂ incorporation on the electrode performance of nanohybrid is more prominent for higher current density and faster scan rate, underscoring the significant enhancement of the electron transport of Co‐Al‐LDH?rG‐O. This is supported by electrochemical impedance spectroscopy. The present study clearly demonstrates the usefulness of the porously assembled hybrid network of graphene and metal oxide nanosheets as an effective platform for exploring efficient LDH‐based functional materials.     

Holey graphene hydrogel with in-plane pores for high-performance capacitive desalination

Capacitive deionization is an attractive approach to water desalination and treatment.To achieve efficient capacitative desalination,rationally designed electrodes with high specific capacitances,conductivities,and stabilities are necessary.Here we report the construction of a three-dimensional (3D) holey graphene hydrogel (HGH).This material contains abundant in-plane pores,offering efficient ion transport pathways.Furthermore,it forms a highly interconnected network of graphene sheets,providing efficient electron transport pathways,and its 3D hierarchical porous structure can provide a large specific surface area for the adsorption and storage of ions.Consequently,HGH serves as a binder-free electrode material with excellent electrical conductivity.Cyclic voltammetry (CV) measurements indicate that the optimized HGH can achieve specific capacitances of 358.4 F.g-1 in 6 M KOH solution and 148 F.g-1 in 0.5 M NaC1 solution.Because of these high capacitances,HGH has a desalination capacity as high as 26.8 mg.g-1 (applied potential:1.2 V;initial NaCl concentration:～5,000 mg.L-1).     

Vertically Aligned Graphene–Carbon Fiber Hybrid Electrodes with Superlong Cycling Stability for Flexible Supercapacitors

Graphene electrode–based supercapacitors are in high demand due to their superior electrochemical characteristics. A major bottleneck of using the supercapacitors for commercial applications lies in their inferior electrode cycle life. Herein, a simple and facile method to fabricate highly efficient supercapacitor electrodes using pristine graphene sheets vertically stacked and electrically connected to the carbon fibers which can result in vertically aligned graphene–carbon fiber nanostructure is developed. The vertically aligned graphene–carbon fiber electrode prepared by electrophoretic deposition possesses a mesoporous 3D architecture which enabled faster and efficient electrolyte‐ion diffusion with a gravimetric capacitance of 333.3 F g^?1 and an areal capacitance of 166 mF cm^?2. The electrodes displayed superlong electrochemical cycling stability of more than 100 000 cycles with 100% capacitance retention hence promising for long‐lasting supercapacitors. Apart from the electrochemical double layer charge storage, the oxygen‐containing surface moieties and α‐Ni(OH)₂ present on the graphene sheets enhance the charge storage by faradaic reactions. This enables the assembled device to provide an excellent gravimetric energy density of 76 W h kg^?1 with a 100% capacitance retention even after 1000 bending cycles. This study opens the door for developing high‐performing flexible graphene electrodes for wearable energy storage applications.     

Hydrogen adsorption on boron doped graphene: an ab initio study

(i)?The electronic and structural properties of boron doped graphene sheets, and (ii)?the chemisorption processes of hydrogen adatoms on the boron doped graphene sheets have been examined by ab initio total energy calculations. In (i)?we find that the structural deformations are very localized around the boron substitutional sites, and in accordance with previous studies (Endo et al 2001 J.?Appl.?Phys. 90 5670) there is an increase of the electronic density of states near the Fermi level. Our simulated scanning tunneling microscope (STM) images, for occupied states, indicate the formation of bright (triangular) spots lying on the substitutional boron (center) and nearest-neighbor carbon (edge) sites. Those STM images are attributed to the increase of the density of states within an energy interval of 0.5?eV below the Fermi level. For a boron concentration of ～2.4%, we find that two boron atoms lying on the opposite sites of the same hexagonal ring (B1-B2 configuration) represents the energetically most stable configuration, which is in contrast with previous theoretical findings. Having determined the energetically most stable configuration for substitutional boron atoms on graphene sheets, we next considered the hydrogen adsorption process as a function of the boron concentration, (ii). Our calculated binding energies indicate that the C-H bonds are strengthened near boron substitutional sites. Indeed, the binding energy of hydrogen adatoms forming a dimer-like structure on the boron doped B1-B2 graphene sheet is higher than the binding energy of an isolated H(2) molecule. Since the formation of the H dimer-like structure may represent the initial stage of the hydrogen clustering process on graphene sheets, we can infer that the formation of H clusters is quite likely not only on clean graphene sheets, which is in consonance with previous studies (Hornek?r et al 2006 Phys.?Rev.?Lett. 97 186102), but also on B1-B2 boron doped graphene sheets. However, for a low concentration of boron atoms, the formation of H dimer structures is not expected to occur near a single substitutional boron site. That is, the formation (or not) of H clusters on graphene sheets can be tuned by the concentration of substitutional boron atoms.     

掺氮石墨烯的制备及其ORR催化性能的研究

由于掺氮石墨烯具有优异的电化学性能,受到研究者的关注,然而在石墨烯掺氮的方法中大部分（热解法、烧结法）需要过高的温度（500-900℃）和较长的反应时间（2-3 h）[1-3]。采用微波等离子体对氧化石墨进行还原改性制备掺氮石墨烯,在低功率条件下反应时间只需20 min就得到了催化活性良好的掺氮石墨烯。掺氮石墨烯的表征技术主要包括Raman和TEM,并使用电化学工作站对掺氮石墨烯进行ORR催化性能评估。     

新型多孔导电陶瓷负载银阴极在锌空气电池中的应用

锌空气电池具有能量密度高、成本低及环保等优势, 其空气电极的优劣对电池的输出性能起到决定性的作用。本研究采用一种新型的多孔钙钛矿氧化物La_0.7Sr_0.3CoO_3-δ(LSC)作为陶瓷基底, 负载银纳米颗粒作为催化剂, 研究其作为锌空电池空气电极的性能。β通过调整制备过程中造孔剂(淀粉)的含量, 优选出性能最佳的Ag-LSC空气电极(阴极), 与锌阳极组装成锌空气电池, 进行电化学性能测试。β结果表明, 当LSC基底的孔隙率为~32%且银含量30 mg/cm²时, 制备的多孔陶瓷负载银阴极组装的锌空气电池功率密度最高(141 mW/cm²)。β在Ag-LSC空气电极表面涂一层聚四氟乙烯(PTFE)疏水材料后, 锌空气电池的使用寿命得到显著延长。     

Organic-acid-assisted synthesis of a 3D lasagna-like Fe-N-doped CNTs-G framework: An efficient and stable electrocatalyst for oxygen reduction reactions

The scalable preparation of multi-functional three-dimensional (3D) carbon nanotubes and graphene (CNTs-G) hybrids via a well-controlled route is urgently required and challenging.Herein,an easily operated,oxalic acid-assisted method was developed for the in situ fabrication of a 3D lasagna-like Fe-N-doped CNTs-G framework (LMFC) from a precursor designed at the molecular level.The well-organized architecture of LMFC was constructed by multi-dimensionally interconnected graphene and CNTs which derived from porous graphene sheets,to form a fundamentally robust and hierarchical porous structure,as well as favorable conductive networks.The impressive oxygen reduction reaction (ORR) performances in both alkaline and acidic conditions helped confirm the significance of this technically favorable morphological structure.This product was also the subject of research for the exploration of decisive effects on the performance of ORR catalysts with reasonable control variables.The present work further advances the construction of novel 3D carbon architectures via practical and economic routes.