氧化石墨烯的可控还原及结构表征

采用氧化还原法, 通过控制还原时间制备了不同还原程度的石墨烯; 用红外光谱、 紫外光谱、 拉曼光谱、 X射线衍射、 热重分析、 电导率测量等多种手段系统研究了不同还原程度石墨烯的结构与性能; 采用透射电子显微镜、 扫描电子显微镜和原子力显微镜比较了氧化石墨烯和石墨烯的形貌. 结果表明, 随着还原程度的增加, 石墨烯中含氧基团减少, 紫外吸收峰逐渐红移, D带与G带的强度比增加, 热稳定性和导电性提高. 微观结构表征说明石墨烯比氧化石墨烯片的厚度增加, 褶皱增多.     

石墨烯的氧化还原法制备及结构表征

采用改进的Hummers法对天然鳞片石墨进行氧化处理制备氧化石墨,经超声分散,然后在水合肼的作用下加热还原制备了在水相条件下稳定分散的石墨烯。用红外光谱、拉曼光谱、扫描探针显微镜和ζ电位仪对样品进行了结构、谱学、形貌和ζ电位分析。结果表明,石墨被氧化后形成以C=O、C-OH、-COOH和C-O-C等官能团形式的共价键型石墨层间化合物;还原氧化石墨后形成的石墨烯表面的官能团与石墨的相似;氧化石墨烯和石墨烯在碱性条件下可形成稳定的悬浮液;氧化石墨烯和石墨烯薄片厚度为1.0nm左右。考察并讨论了还原过程中水合肼用量,体系反应温度、反应时间和pH值对石墨烯还原程度和稳定性的影响,水合肼用量和反应时间是影响石墨烯还原程度的主要因素;pH值对石墨烯稳定性影响较大。     

水溶液体系中氧化石墨烯的γ射线辐射还原

石墨烯是一种碳原子以二维蜂窝状晶格结构构成的单片层材料,由于其具有优异的电传导性、力学性能和热传导性近年来受到广泛关注.本文采用γ射线辐射技术分别处理水溶液和对苯二胺(PPD)水溶液中的氧化石墨烯(GO),得到辐照还原氧化石墨烯(RGO)和胺基化修饰的还原氧化石墨烯(RGON).通过傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、拉曼(Raman)光谱、X射线衍射(XRD)和热失重分析(TGA)等表征分析产物的化学结构和元素组成;通过四探针测试仪和接触角测量仪研究产物的导电性能和亲水性.实验结果表明,在水溶液及PPD水溶液中γ射线辐射均可高效还原GO,还原后得到的RGO和RGON电导率均显著增大.PPD的胺基在辐射还原过程中还可以修饰到石墨烯的表面,因此RGON的亲水性比RGO好,但胺基的存在会干扰石墨烯表面π电子的传导,导致其电导率下降.     

正丁基氯化镁还原氧化石墨烯的表征

采用元素分析、红外光谱(FTIR)、X射线光电子能谱(XPS)、拉曼光谱、X射线衍射(XRD)、固体¹³C核磁共振波谱(¹³C MAS NMR)、热失重分析(TGA)、导电率测试以及原子力显微镜(AFM)等手段对正丁基氯化镁还原的氧化石墨烯进行了系统的表征. 结果表明, 正丁基氯化镁可以有效还原氧化石墨烯, 随着其用量的增加, 氧化石墨烯还原程度增加, 碳/氧摩尔比升高, 片层间距减小, 热稳定性增强, 导电率增大(可达3.6×10² S/m). 还原后部分氧化石墨烯片层发生聚集.     

乙醇胺功能化石墨烯的制备与表征

乙醇胺在温和条件下与氧化石墨烯反应, 然后经水合肼还原得到功能化的石墨烯. 干燥的功能化石墨烯经超声处理后, 可稳定分散于水、乙醇、丙酮和N,N二甲基甲酰胺(DMF)等溶剂中. 原子力显微镜(AFM)、透射电镜(TEM)分析表明功能化石墨烯平均厚度为3～4 nm. 傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、X射线衍射(XRD)对功能化石墨烯的结构分析表明: 乙醇胺与氧化石墨烯发生了化学反应, 并通过共价键连接到石墨烯的六元环上. TG结果表明功能化石墨烯的热稳定性比氧化石墨烯有所提高, 但低于还原氧化石墨烯.     

KH-570功能化石墨烯的制备与表征

采用Hummers法对天然石墨进行氧化处理制备了氧化石墨烯,通过γ-甲基丙烯酰氧丙基三甲氧基硅烷与氧化石墨烯反应得到功能化氧化石墨烯,然后在水合肼的作用下制备了功能化石墨烯。未烘干的功能化石墨烯在超声处理下,能稳定分散在体积比为9∶1(V/V)的乙醇/水、丙酮/水或N,N-二甲基甲酰胺/水的混合溶剂中。用傅立叶变换红外光谱、原子力显微镜、X射线光电子能谱及X射线衍射对样品结构、形貌进行了分析。结果表明,KH-570上的硅氧烷与氧化石墨烯上的羟基发生了反应,经水合肼还原后,功能化石墨烯的无序度增加,层间距也比功能化氧化石墨烯的缩小了。功能化石墨烯在DMF/水中呈高度剥离状态,片层厚度为1.1～2.3 nm。     

氧化石墨烯水热还原前后的发光光谱

分别采用改进Hummers方法和水热还原法制备了氧化石墨烯(GO)和还原氧化石墨烯(RGO)。 GO和RGO经透射电子显微镜(TEM)、紫外-可见吸收光谱(UV-Vis)、红外光谱(IR)、荧光发射和激发光谱(PL、PLE)等技术手段进行了表征。 荧光发射光谱显示,氧化石墨烯(GO)在可见光的激发下可以得到波长在600~800 nm范围内的宽谱近红外荧光。 通过比较氧化石墨烯水热还原前后的光谱变化,发现氧化石墨烯近红外荧光起源于氧化石墨烯的表面含氧基团,如C=O、COOH。 近红外荧光穿透性好、对生物组织损坏小,非常适合于生物成像,预示着氧化石墨烯在生物成像方面的应用潜力。     

氮掺杂还原氧化石墨烯负载铂催化剂的制备及甲醇电氧化性能

采用高温热解聚苯胺修饰的氧化石墨烯（PANI-GO）,得到了氮掺杂的还原氧化石墨烯碳材料（N-RGO）,以其负载Pt 制备了Pt/N-RGO纳米结构电催化剂. 采用透射电镜（TEM）、X射线光电子能谱（XPS）、X 射线衍射（XRD）谱及拉曼光谱等技术对N-RGO和Pt/N-RGO的形貌及结构进行了表征,用循环伏安、计时电流等电化学技术研究了Pt/N-RGO电极催化剂对CO溶出反应和甲醇电氧化反应的催化性能. 结果表明：高温热解PANIGO可同时实现GO的还原及其氮掺杂的过程,氮掺杂引起还原氧化石墨烯碳材料表面缺陷结构和导电性的增加;与相应的未掺杂氮样品Pt/RGO相比较,Pt/N-RGO样品上Pt 颗粒的分散更均匀,显示出更强的抗CO毒化能力和更高的甲醇电氧化催化活性及稳定性.     

自由基反应诱导的溴功能化还原氧化石墨烯的制备

以氧化石墨烯(GO)为原料,N-溴代丁二酰亚胺(NBS)为溴代试剂,硫代硫酸钠为还原剂,通过羧基化、溴化和还原三步法,采用自由基反应的方式制备了溴功能化还原氧化石墨烯(rGOBr).通过X射线衍射、扫描电子显微镜、红外光谱、拉曼光谱以及X射线光电子能谱等手段对rGOBr的结构、微观形貌和元素组成进行了表征.结果表明,溴元素以共价键的形式分布在石墨烯表面.本方法原料来源广泛、操作简单且条件温和,为石墨烯的溴功能化提供了一条新途径.     

氮掺杂还原氧化石墨烯负载铂催化剂的制备及甲醇电氧化性能

采用高温热解聚苯胺修饰的氧化石墨烯(PANI-GO),得到了氮掺杂的还原氧化石墨烯碳材料(N-RGO),以其负载Pt制备了Pt/N-RGO纳米结构电催化剂.采用透射电镜(TEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)谱及拉曼光谱等技术对N-RGO和Pt/N-RGO的形貌及结构进行了表征,用循环伏安、计时电流等电化学技术研究了Pt/N-RGO电极催化剂对CO溶出反应和甲醇电氧化反应的催化性能.结果表明:高温热解PANIGO可同时实现GO的还原及其氮掺杂的过程,氮掺杂引起还原氧化石墨烯碳材料表面缺陷结构和导电性的增加;与相应的未掺杂氮样品Pt/RGO相比较,Pt/N-RGO样品上Pt颗粒的分散更均匀,显示出更强的抗CO毒化能力和更高的甲醇电氧化催化活性及稳定性.     

Experimental study on thermo-physical and rheological properties of stable and green reduced graphene oxide nanofluids: Hydrothermal assisted technique

In this study a dehydration hydrothermal technique has been used to introduce a simple, environmentally friendly and facile method for manufacturing highly dispersed reduced graphene oxide for improving the thermo-physical and rheological properties of heat transfer liquids. The hydrothermal reduction of graphene oxide was verified by various characterizations methods such as UV–visible absorption spectroscopy, Zeta potential, Raman spectroscopy, X-ray photoemission spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. A thorough investigation was conducted on the thermo-physical properties of reduced graphene oxide at concentrations of 0.02, 0.04, 0.06, and 0.08?wt% under different temperatures. Significant improvements in electrical and thermal conductivity were obtained by adding a small amount of hydrothermal-assisted reduced graphene oxide (h-rGO) in the suspension. The viscosity and density remained relatively unchanged with the increase of concentrations where the pH was maintained within the desirable value, despite the fact that no additive was used during the reduction process. It is noteworthy to highlight that the h-rGO aqueous suspensions have shown Newtonian behavior. Results indicated that the h-rGO could be employed as a promising additive for conventional heat transfer liquids for different thermal applications.     

Solvothermal reduction of graphene oxide in dimethylformamide

The reduction of graphene oxide (G-O) is one of the most promising methods for the large scale production of graphene-based materials. In this paper, we report a simple and non-toxic method to produce reduced graphene oxide (rG-O) by refluxing G-O in N, N-dimethylformamide without the aid of a reducing agent. The rG-O materials with high degrees of reduction are prepared and the levels of reduction are controlled using reflux time. Successful reduction is confirmed by combustion-based elemental analysis and X-ray photoelectron and Fourier transform infrared spectroscopy.     

Magnetic property and structural study of nickel supported on reduced graphene oxide prepared by chemical vapor deposition

Nickel supported on reduced graphene oxide was synthesized by chemical vapor deposition technique. The crystal structure and magnetic properties of the prepared sample were studied by means of Raman spectrometry, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), and vibrating sample magnetometry (VSM). The result of Raman spectroscopy revealed the structure of few-layer graphene as the support for Ni nanoparticles. XP spectrum confirmed the presence of metallic Ni on the a few-layer graphene surface. TE micrograph showed that the nickel nanoparticles were sphere shaped and the mean particle size is about 20 nm deposited on the reduced graphene oxide. The magnetic study showed the ferromagnetic behavior of 3.2 wt% nickel over reduced graphene oxide at room temperature.     

Graphene oxide modifications induced by excimer laser irradiations

The properties of graphene oxide foils were modified by excimer laser irradiation at different fluences and times. The irradiations were performed in air and in vacuum using a pulsed UV laser operating at 248-nm wavelength and 23-ns pulse duration. Measurements of ablation yield, microscope surface morphology and Raman spectroscopy were performed. The residual surface shows a significant oxygen reduction due to the removing of functional oxygen groups, a thickness reduction due to the removal of graphene layers depending on the used laser shots and a presence of defects in the graphene sheets as evident by the Raman spectroscopy investigation.     

Preparation of different graphene nanostructures for hydrogen adsorption

In this study, different types of graphene were synthesized to investigate hydrogen adsorption capacity at different pressures (0–34 bar) at room temperature (298 K). Graphene and nanoporous graphene were prepared by Chemical Vapor Deposition (CVD) method, using methane as a carbon source at a temperature of 900 °C over copper plates and nickel oxide nanocatalyst. The nickel oxide nanocatalyst was prepared by sol–gel method, whereas graphene oxide was prepared through modified Hummer's method. The products were characterized by X‐ray diffraction, field emission‐scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller and Raman spectroscopy. The adsorption of hydrogen was done by volumetric method. High adsorption capacity was achieved in nanoporous graphene because of its high pore volume (2.11 cm³/g) and large specific surface area (850 m²/g). Hydrogen adsorption values for nanoporous graphene, graphene and graphene oxide were determined as 2.56, 1.70 and 0.74 wt%, respectively. In addition, the hydrogen adsorption of graphene nanostructures fitted nicely to the selected two‐parameter and three‐parameter adsorption isotherm models. The adsorption isotherm model coefficients have been found for a 0–34 bar pressure range. The parameter values for all adsorbents showed proper conformity to the model and experimental data. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrochemistry at chemically modified graphenes

Electrochemical applications of graphene are of great interest to many researchers as they can potentially lead to crucial technological advancements in fabrication of electrochemical devices for energy production and storage, and highly sensitive sensors. There are many routes towards fabrication of bulk quantities of chemically modified graphenes (CMG) for applications such as electrode materials. Each of them yields different graphene materials with different functionalities and structural defects. Here, we compare the electrochemical properties of five different chemically modified graphenes: graphite oxide, graphene oxide, thermally reduced graphene oxide, chemically reduced graphene oxide, and electrochemically reduced graphene oxide. We characterized these materials using transmission electron microscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, which allowed us to correlate the electrochemical properties with the structural and chemical features of the CMGs. We found that thermally reduced graphene oxide offers the most favorable electrochemical performance among the different materials studied. Our findings have a profound impact for the applications of chemically modified graphenes in electrochemical devices.     

氮掺杂还原氧化石墨烯/四氧化三钴双功能催化剂的制备及表征

采用尿素作为氮源,通过热退火法制备氮掺杂还原氧化石墨烯,然后以乙酰丙酮钴作为钴源通过水热法制备氮掺杂还原氧化石墨烯/四氧化三钴杂化纳米片作为催化氧还原和氧析出反应的双功能催化剂。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线电子能谱仪(XPS)等对其进行形貌结构表征,通过旋转圆盘电极等电化学测试对其电催化性能进行分析,可以看出该催化剂具有良好的氧还原和氧析出催化性能。     

Ultrafast room-temperature reduction of graphene oxide by sodium borohydride,sodium molybdate and hydrochloric acid

Since graphene-based materials have shown great potential in many fields,it is important to explore ultrafast and high-efficient methods to synthesize reduced graphene oxide(rGO) using inexpensive reducing agents under mild conditions.Here,we reported a novel method for the ultrafast chemical reduction of graphene oxide(GO) at room temperature using sodium borohydride(NaBH₄),sodium molybdate(Na₂MoO₄) and hydrochloric acid(HCl).The reduction was carried out within 2 min.A series of characterization results revealed that the obtained reduced graphene oxide has higher reduction degree than that synthesized by NaBH₄ alone at high temperature.Moreover,rGO electrode based on the present reducing method exhibited a superior specific capacitance of 139.8 F/g at a current density of1 A/g,indicating that it can be used as electrode materials for supercapacitors.