Nitrogen-doped holey graphene nanoscrolls for high-energy and high-power supercapacitors

Porous structure and heteroatom doping are two key parameters for significantly boosting the capacitive performance of graphene-based materials.Herein,we report a facile approach to prepare onedimensional(ID) nitrogen-doped holey graphene nanoscrolls(NHGNSs) through cold quenching treatment of two-dimensional graphene oxide sheets,followed by thermal annealing in the successive atmosphere of NH_3 and air.Benefiting from the synergy of the unique 1D tubular morphology,abundant nanoholes and nitrogen doping,the NHGNSs exhibit a high specific capacitance of 126 F/g at 1 A/g in ionic liquid electrolyte and excellent rate capability with 81% of the capacitance retained at 20 A/g.Furthermore,the fabricated symmetric supercapacitors based on NHGNSs achieve both high energy density of 53.5 Wh/kg at 875 W/kg and high power density of 17.5 kW/kg at 43.4 Wh/kg.The simple synthetic process and superior electrochemical performance suggest the great potential of NHGNSs for supercapacitor application.     

Enhanced electrochemiluminescence based on Ru(bpy)32+-doped silica nanoparticles and graphene composite for analysis of melamine in milk

A sensitive electrochemiluminescence (ECL) sensor for melamine analysis was fabricated based on Ru(bpy)₃²⁺-doped silica (Ru(bpy)₃²⁺@SiO₂) nanoparticles and graphene composite. Spherical Ru(bpy)₃²⁺@SiO₂ nanoparticles with uniform size about 55 nm were prepared by the reverse microemulsion method. Since per Ru(bpy)₃²⁺@SiO₂ nanoparticle encapsulated a great deal of Ru(bpy)₃²⁺, the ECL intensity has been greatly enhanced, which resulted in high sensitivity. Due to its extraordinary electric conductivity, graphene improved the conductivity and accelerated the electron transfer rate. In addition, graphene could work as electronic channel improving the efficient luminophor amount participating in the ECL reaction, which further enhanced the ECL signal. This proposed sensor was used to melamine analysis and the ECL intensity was proportional to logarithmic melamine concentration range from 1 × 10⁻¹³ M to 1 × 10⁻⁸ M with the detect limit as low as 1 × 10⁻¹³ M. In application to detect melamine in milk, satisfactory recoveries could be obtained, which indicated this sensor having potential application in melamine analysis in real samples.     

Synergistic effect between expandable graphite and ammonium polyphosphate on flame retarded polylactide

Synergistic effect was observed between expandable graphite (EG) and ammonium polyphosphate (APP) on flame retarded polylactide (PLA) in this paper using limiting oxygen index (LOI), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray spectroscopy (XPS) and cone calorimeter tests etc. In the experiments, PLA composites with 15 wt% of APP/EG(1:3) combinations showed a LOI value of 36.5 and V-0 rating in UL-94 tests, greatly improved flame retardant properties from composites with APP or EG alone. Results from TGA and cone calorimeter demonstrated that APP/EG combination could retard the degradation of polymeric materials above the temperature of 520 °C by promoting the formation of a compact char layer. This char layer protects the matrix effectively from heat penetrating inside and prevents its further degradation, resulting in lower weight loss rate and better flame retarded performance.     

High voltage supercapacitors using hydrated graphene film in a neutral aqueous electrolyte

The potential stability windows of chemical converted graphene in different aqueous electrolyte solutions were investigated for the first time. Based on this result, a supercapacitor with a high voltage and long cycle-life was prepared with the hydrated graphene films in the neutral aqueous solution at the maximum voltage of 1.6 and even 1.8 V. The electrochemical performance of the obtained sample was systematically investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the cyclic voltammetry, hydrated graphene film can still retain rectangular shape at the high scan rate of 0.5 V/s in the neutral aqueous electrolyte. At a galvanostatic charge/discharge rate of 1 or 200 A/g, the specific capacitance of 202.3 or 138.1 F/g was delivered, respectively. Furthermore, the EIS results also confirm its fast neutral ion diffusion and high operating frequency of 9.34 Hz.     

Hydrothermal synthesis of reduced graphene sheets/Fe2O3 nanorods composites and their enhanced electrochemical performance for supercapacitors

Reduced graphene nanosheets/Fe₂O₃ nanorods (GNS/Fe₂O₃) composite has been fabricated by a hydrothermal route for supercapacitor electrode materials. The obtained GNS/Fe₂O₃ composite formed a uniform structure with the Fe₂O₃ nanorods grew on the graphene surface and/or filled between the graphene sheets. The electrochemical performances of the GNS/Fe₂O₃ hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests in 6 M KOH electrolyte. Comparing with the pure Fe₂O₃ electrode, GNS/Fe₂O₃ composite electrode exhibits an enhanced specific capacitance of 320 F g⁻¹ at 10 mA cm⁻² and an excellent cycle-ability with capacity retention of about 97% after 500 cycles. The simple and cost-effective preparation technique of this composite with good capacitive behavior encourages its potential commercial application.     

Surface modulated hierarchical graphene film via sulfur and phosphorus dual-doping for high performance flexible supercapacitors

The steam-assistant heteroatoms of sulfur and phosphorus dual-doped graphene film fabricated via an ice-template and thermal-activation approach demonstrates an excellent pseudocapacitive behavior in flexible electrochemical capacitors.     

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

The ease of undesirable agglomeration and a low efficiency are two problems that restrict the application of graphite nanoplatelets (GNPs) in epoxy resins (EP). Herein, a new strategy with melamine (MEL) as the precursor to functionalize GNPs chemically, which form a bonding layer that is compatible with epoxy matrix, is reported. The MEL fragments with secondary amine groups were grafted uniformly on the GNPs surface by covalent junctions to exploit the diazonium chemistry. This behavior led to a better dispersion and a stronger interaction with the epoxy matrix and resulted in an enhanced glass transition temperature and bending strength, compared with the pure EP. When only 1 wt% functionalized GNPs (f‐GNPs) was used, the Tg of the modified EP raised of about 15°C compared with pure EP, and the bending strength increased by approximately 39%. The dielectric constant of the EP with f‐GNPs was impacted slightly, and the dielectric loss decreased. At 10⁵ Hz, the dielectric loss of the EP with 1 wt% f‐GNPs decreased by approximately 11% compared with pure EP. Therefore, diazotization modification of the GNPs is a useful approach to improve the compatibility in nanoparticle networks.     

A liquid phosphorous flame retardant combined with expandable graphite or melamine in flexible polyurethane foam

A systematic series of flexible polyurethane foams (FPUF) with different concentrations of flame retardants, bis([dimethoxyphosphoryl]methyl) phenyl phosphate (BDMPP), and melamine (MA) or expandable graphite (EG) was prepared. The mechanical properties of the FPUFs were evaluated by a universal testing machine. The pyrolysis behaviors and the evolved gas analysis were done by thermogravimetric analysis (TGA) and TGA coupled with Fourier-transform infrared (TG-FTIR), respectively. The fire behaviors were studied by limiting oxygen index (LOI), UL 94 test for horizontal burning of cellular materials (UL 94 HBF), and cone calorimeter measurement. Scanning electronic microscopy (SEM) was used to examine the cellular structure's morphology and the postfire char residue of the FPUFs. LOI and UL 94 HBF tests of all the flame retarded samples show improved flame retardancy. BDMPP plays an essential role in the gas phase because it significantly reduces the effective heat of combustion (EHC). This study highlights the synergistic effect caused by the combination of BDMPP and EG. The measured char yield from TGA is greater than the sum of individual effects. No dripping phenomenon occurs during burning for FPUF-BDMPP-EGs, as demonstrated by the result of the UL 94 HBF test. EG performs excellently on smoke suppression during burning, as evident in the result of the cone calorimeter test. MA reduces the peak heat release rate (pHRR) significantly. The synergistic effect of the combination of BDMPP and EG as well as MA offers an approach to enhance flame retardancy and smoke suppression.     

Surface modification by graphene oxide:An efficient strategy to improve the performance of activated carbon based supercapacitors

An efficient and cost-effective strategy to modificate the surface of active carbon (AC), form a 3D-conductive network, and therefore improve the electrochemical performance of AC based supercapacitor was developed.     

Synthesis and characterization of expandable graphite-poly(methyl methacrylate) composite particles and their application to flame retardation of rigid polyurethane foams

The expandable graphite (EG) is well proved to be a good intumescent flame retardant for rigid polyurethane foam (RPUF), however, as it is pulverized into fine particles (pEG) for the purpose of improving the mechanical properties of the foam composite, the flame-retardant properties of pEG-filled RPUF (pEG/RPUF) are deteriorated. To improve both the mechanical properties and flame-retardant performance of pEG/RPUF composite, the pEG particles were encapsulated with a layer of polymer, poly(methyl methacrylate) (PMMA). The Fourier transform infrared spectroscopy (FTIR) examination, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) observation well demonstrated that the pEG-PMMA particles were successfully synthesized via emulsion polymerization, with 22.09 wt% PMMA. In contrast to the pEG, the addition of 10 wt% of pEG-PMMA particles into RPUF led to a considerable increase of the compressive strength and modulus and flame retardancy (limiting oxygen index, horizontal and vertical burning rates). The improvement of mechanical properties and flame-retardant behavior of pEG-PMMA particles filled RPUF was attributed to the desirable dispersion of pEG in PU matrix without destroying the integrality of the RPUF cell system, the good interfacial adhesion between PMMA and RPUF, and sealing the fine EG particles without losing oxidant, hence, to increase their expanded volume as exposed to fire.     

Free-standing nitrogen doped graphene/Co(OH)_2 composite films with superior catalytic activity for aprotic lithium-oxygen batteries

The recent boom in large-scale energy storage system promotes the development of lithium-oxygen batteries because of their high theo retical energy density.However,their applications are still limited by the sluggish kinetic,insoluble discharge product deposition and the undesired parasitic reaction.Herein,the free-standing nitrogen doped reduced graphene oxide/Co(OH)_2(NRGO/Co(OH)_2) composite films were prepared by a facile hydrothermal method,The NRGO/Co(OH)_2 composite films display interconnected three-dimensional conductive network,which can not only promote the diffusion of O_2 and the transport of electrolyte ions,but also provide abundant storage space for discharge products.Moreover,the introduction of nitrogen-containing functional groups results in improved conductivity and electron adsorption ability,which can facilitate electron transport and enhance the surface catalytic activity.Combining with excellent catalytic performance,the lithium-oxygen batteries with NRGO/Co(OH)_2 composite film cathodes deliver low charge overpotential and excellent cycling performance.     

聚苯胺改性氮掺杂碳纳米管制备及其超级电容器性能

利用苯胺原位化学聚合合成聚苯胺包覆碳纳米管(CNTs), 再炭化处理制备氮掺杂碳纳米管(NCNTs).激光拉曼(Raman)光谱和X射线光电子谱(XPS)分析及透射电镜(TEM)观察表明, 苯胺包覆碳纳米管经炭化处理后, 得到以碳纳米管为核、氮掺杂碳层为壳, 具有核-壳结构的氮掺杂碳纳米管, 而碳纳米管本征结构未遭破坏. 研究表明, 随着苯胺用量的增大, 氮掺杂碳纳米管的氮掺杂碳层变厚, 氮含量从7.06%(质量分数)增加到8.64%, 而作为超级电容器电极材料, 随着氮掺杂碳层厚度降低, 氮掺杂碳纳米管在6 mol·L^-1氢氧化钾电解液中的比容量从107 F·g^-1增大到205 F·g^-1, 远高于原始碳纳米管10 F·g^-1的比容量, 且聚苯胺改性氮掺杂碳纳米管表现出较好的充放电循环性, 经1000次充放电循环后仍保持初始容量的92.8%~97.1%, 表明氮掺杂碳纳米管不仅通过表面氮杂原子引入大的法拉第电容和改善亲水性使电容量显著增大, 其具有的核壳结构特征也使循环稳定性增强。     

Green synthesis of graphene nanosheets/ZnO composites and electrochemical properties

A green and facile approach was demonstrated to prepare graphene nanosheets/ZnO (GNS/ZnO) composites for supercapacitor materials. Glucose, as a reducing agent, and exfoliated graphite oxide (GO), as precursor, were used to synthesize GNS, then ZnO directly grew onto conducting graphene nanosheets as electrode materials. The small ZnO particles successfully anchored onto graphene sheets as spacers to keep the neighboring sheets separate. The electrochemical performances of these electrodes were analyzed by cyclic voltammetry, electrochemical impedance spectrometry and chronopotentiometry. Results showed that the GNS/ZnO composites displayed superior capacitive performance with large capacitance (62.2 F/g), excellent cyclic performance, and maximum power density (8.1 kW/kg) as compared with pure graphene electrodes. Our investigation highlight the importance of anchoring of small ZnO particles on graphene sheets for maximum utilization of electrochemically active ZnO and graphene for energy storage application in supercapacitors.     

耦合氧化石墨烯的N掺杂Bi_2O_2CO_3微球光催化性能增强机制(英文)

光催化作为一种环境友好技术,在解决环境污染和能源匮乏问题方面展现出巨大应用潜力.TiO_2因其化学稳定性、无毒和低成本被广泛应用于能源转换和污染物降解等领域,但其快速的电子-空穴复合与低太阳能利用率等限制了其在光催化中的潜在应用.因此,寻找新的有优越可见光活性的催化剂是一个挑战.最近,(BiO)_2CO_3因其独特的形貌、化学稳定性和较高的催化效率成为有前景的光催化剂.然而,(BiO)_2CO_3较大的带隙限制了对太阳光的利用,快速的电子-空穴复合阻碍了光催化性能的提高.因此,提高(BiO)_2CO_3的光催化效率是当务之急.近期研究表明,通过与氧化石墨烯杂交提高载流子的分离能力,可有效增强光催化性能.基于此,我们设计并合成了一种氮掺杂的(BiO)_2CO_3与氧化石墨烯(GO)耦合的新型光催化剂(N-BOC-GO).首先,通过一步水热法合成了N-BOC-GO微球.N-BOC-GO光催化剂对NO可见光光催化去除性能达到62%.采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis)和光致发光光谱(PL)等表征手段研究了N-BOC-GO的光催化性能增强机制.从N-BOC-GO的XRD谱中没有发现GO的衍射峰,说明加入的GO分散度高;N-BOC-GO中的BOC晶格参数没有发生变化,说明GO没有进入BOC晶格,但加入GO增强了N-BOC的结晶度.XPS结果表明,与N-BOC相比,N-BOC-GO的峰位置发生了明显位移,表明N-BOC和GO之间存在强相互作用.此外,FT-IR和拉曼光谱证明了在复合物中存在GO.SEM表明,N-BOC规则地团聚成微球,且微球被固定在有褶皱的GO片上.这说明GO与N-BOC的作用是静电作用或物理作用,在光激发过程中有利于N-BOC微球上的电子转移到GO片上.UV-Vis图谱中,N-BOC-GO表现出明显增强的可见光吸收,说明加入GO会明显提高N-BOC的吸收能力.此外,3D分层结构会通过SSR效应提高光吸收.从PL图可以发现,N-BOC-GO的电子-空穴复合明显下降,说明GO可以转移电子从而提高光催化性能.结合前面的分析,我们提出了N-BOC-GO光催化剂3D分层结构的形成和性能增强机制.在水热过程中,通过分子间相互作用使N-BOC自组装成块,随后在表面能最小化的作用下转化成3D微球.加入GO后,N-BOC和GO通过物理吸附使得N-BOC微球均匀分散在GO上,最后N-BOC-GO的形貌类似于玫瑰花和其叶子的组合.在可见光照射下,N-BOC产生电子-空穴对,电子从N-BOC表面转移到GO表面,表明GO可作为电子的收集者和传递者以有效分离电子-空穴对,延长载流子寿命.N-BOC价带上的空穴可以直接氧化NO或产生?OH氧化NO.此外,由于GO独特的特征,光催化反应发生在N-BOC催化剂表面和GO片上,从而提高了反应空间位点.故引入GO于N-BOC体系中可有效分离光生载流子和提高反应活性位点,从而显著提高可见光催化性能.     

Design and construction of three-dimensional graphene/conducting polymer for supercapacitors

Three-dimensional graphene/conducting polymer(3DGCP) composites have received significant attention in recent years due to their unique structures and promising applications in energy storage.With the structural diversity of graphene and π-functional conducting polymers via rich chemical routes,a number of 3DGCP composites with novel structures and attractive performance have been developed.Particularly,the hierarchical porosity,the interactions between graphene and conducting polymers as well as the their synergetic effects within 3DGCP composites can be well combined and elaborated by various synthetic methods,which made 3DGCP composites show unique electrochemical properties and significantly improved performance in energy storage fields compared to other graphenebased composites.In this short review,we present recent advances in 3DGCP composites in developing effective strategies to prepare 3DGCP composites and exploring them as a unique platform for supercapacitors with unprecedented performance.The challenges and future opportunities are also discussed for promotion of further study.     

Facile synthesis of cobalt oxide/reduced graphene oxide composites for electrochemical capacitor and sensor applications

Reduced graphene oxide sheets decorated with cobalt oxide nanoparticles (Co₃O₄/rGO) were produced using a hydrothermal method without surfactants. Both the reduction of GO and the formation of Co₃O₄ nanoparticles occurred simultaneously under this condition. At the same current density of 0.5 A g⁻¹, the Co₃O₄/rGO nanocomposites exhibited much a higher specific capacitance (545 F g⁻¹) than that of bare Co₃O₄ (100 F g⁻¹). On the other hand, for the detection of H₂O₂, the peak current of Co₃O₄/rGO was 4 times higher than that of Co₃O₄. Moreover, the resulting composite displayed a low detection limit of 0.62 μM and a high sensitivity of 28,500 μA mM⁻¹cm⁻² for the H₂O₂ sensor. These results suggest that the Co₃O₄/rGO nanocomposite is a promising material for both supercapacitor and non-enzymatic H₂O₂ sensor applications.     

Synthesis of zeolitic imidazolate framework-67 nanocube wrapped by graphene oxide and its application for supercapacitors

Journal of Solid State Electrochemistry - In this study, a nanocube of zeolitic imidazolate framework-67 (ZIF-67) was prepared by blending cobalt nitrate hexahydrate and 2-methylimidazole together...     

组氨酸和五乙烯六胺功能化掺硼石墨烯量子点的合成及荧光检测中草药中姜黄素

Citric acid,histidine,pentaethylenehexamine and boric acid were mixed and pyrolyzed to prepare histidine and pentaethylenehexamine-functionalized and boron-doped graphene quantum dots （HPB-GQD）. The resulting HPB-GQD was composed of graphene sheets with size of 4.17±0.12 nm, and also with rich functional groups at the edges of graphene sheets. The fluorescence emission of HPB-GQD depended on the excitation wavelength. Ultraviolet excitation at 375 nm produced the strongest blue fluorescence emission. The fluorescence quantum yield was 87.4%, which was significantly better than that of traditional GQD,and single histidine, pentaethylenehexamine or boric acid-functionalized GQD,showing that introduction of histidine, pentaethylenehexamine and boron can significantly improve the luminescence efficiency. Based on the fluorescence quenching by the interaction between curcumin and HPB-GQD, a method for fluorescence determination of curcumin was established. The linear range and detection limit were 0.05-20.0 μmol/L and 0.017 μmol/L,respectively. The proposed method has been successfully applied to the fluorescence detection of curcumin in Chinese herbal medicine. The results were basically consistent with those of liquud chromatographymass spectrometry（LC-MS）and the recoveries were in the range of 96.0%-104.0%. © 2023 The Authors.     

氮掺杂石墨烯的制备及其超级电容性能

以氧化石墨烯(GO)为原料, 尿素为还原剂和氮掺杂剂, 采用水热法合成了氮掺杂石墨烯. 利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外(FTIR)光谱、X 射线衍射(XRD)、X 射线光电子能谱(XPS)、氮气吸脱附分析、电导率和电化学测试对样品的形貌、结构、组成以及电化学性质进行表征. 结果表明:水热条件下尿素能有效地化学还原GO并对其进行氮掺杂; 通过调节原料与掺杂剂的质量比, 可以得到不同氮掺杂含量的石墨烯, 氮元素含量范围为5.47%-7.56% (原子分数); 在6 mol·L^-1的KOH电解液中, 氮元素含量为7.50%的掺杂石墨烯的超级电容性能最优, 即在3 A·g^-1电流密度下首次恒流充放电比电容可达184.5 F·g^-1, 经1200次循环后的比电容为161.7 F·g^-1, 电容保持率为87.6%.     

UPLC-MRM法测定饲料中的三聚氰胺

提出了一种UPLC-MRM测定饲料中微量三聚氰胺的分析方法. 饲料经10 g/L三氯乙酸溶液提取和22 g/L乙酸铅溶液沉淀蛋白质, 过混合型阳离子交换柱(MCX)纯化, 离心后用0.45 μm滤膜过滤, 用超高效液相色谱-质谱-质谱联用仪(UPLC-MS-MS)分析测定, 以三聚氰胺母离子126.9 (m/z)和子离子67.5与84.6 (m/z)定性、定量目标物. 饲料样品加标回收率(n=6)为84.5%, 检测限0.01 μg/L, 相对偏差(RSD) 6.5%.