氧化石墨烯的还原研究进展

石墨烯自首次被Novoselov和Geim等发现和报道后,因其特殊的光、电、热及力学等优异性能而受到广泛研究。在众多制备石墨烯的方法中,还原氧化石墨烯是目前最有希望实现大规模生产石墨烯的方法。鉴于此,重点回顾和比较了国内外氧化石墨烯的还原方法,其间介绍了部分还原机理,并预测了未来发展的趋势。     

选择性还原氧化石墨烯(英文)

还原氧化石墨烯已被广泛用于制备基于石墨烯的材料。目前,还原处理方法均是尽可能地将氧化石墨烯中的功能团去除,恢复石墨烯的电子结构。由于氧化石墨烯中氧基功能团(如羟基、羧基及环氧基)不同的反应活性,氧化石墨烯是可能通过分步的方法进行还原。利用醇溶剂如乙醇、乙二醇、丙三醇还原氧化石墨烯,并采用不同分析手段对样品进行表征。结果发现,在一定条件下这些醇可选择性地还原氧化石墨烯。经这些醇的处理后,氧化石墨烯中环氧功能团被大部分去除,而其他的功能团如羟基和羧基仍被保留。这种选择性去除氧化石墨烯表面功能团的方法可利于有效地控制氧化石墨烯的还原程度、获得具有特定功能团的石墨烯衍生物,从而扩大这类材料的使用范围。     

水合肼还原氧化石墨烯的研究

通过改进的Hummers法制备氧化石墨,将获得的氧化石墨进行热剥离以及超声剥离得到双层甚至单层的氧化石墨烯片.然后采用化学还原-水合肼还原的方法去除氧化石墨烯所含的羧基COOH、羟基OH、羰基C=O和环氧基等化学基团.本实验着重研究了还原剂的用量和反应时间对各个化学基团的影响规律.     

利用维生素C和茶多酚还原氧化石墨烯及其表征

采用改进的Hummers法制备氧化石墨烯(Graphene oxide,GO),以环境友好和具有较强还原能力的茶多酚和维生素C为还原剂还原GO制备还原氧化石墨烯(Reduced graphene oxide,RGO).傅里叶变换红外光谱(FT-IR)测得还原后的RGO的含氧官能团吸收峰明显降低,在X射线衍射图谱(XRD)中观察到还原后的RGO的吸收峰位置的变化,原子力显微镜(AFM)观察到样品的厚度.这些表征数据表明实验采用的两种还原剂成功还原了GO制备出RGO.     

高速剪切辅助氧化还原法制备石墨烯

采用改进的Hummers法制备氧化石墨(GO),氧化石墨经高剪切分散乳化机高速剪切处理后进行超声波处理剥离得到氧化石墨烯,然后经水合肼还原得到石墨烯。利用激光粒度仪、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、热重分析仪(TGA)、激光拉曼光谱仪(Raman)和四探针测试仪等对氧化石墨和石墨烯的形貌及结构进行表征。将高剪切处理制备的石墨烯和未经高剪切处理制备的石墨烯进行对比,结果表明,高速剪切作用对氧化石墨的减薄和剥离有明显促进作用,有利于氧化石墨的还原,提高了石墨烯的制备效率和质量。     

氧化石墨烯/热还原氧化石墨烯改性砂浆的力学/电学性能研究

研究了热还原氧化石墨烯(TRGO)和氧化石墨烯(GO)在水泥砂浆环境下的分散机理,探索了这两种导电相的单掺和复掺对砂浆力学/电学性能的影响。研究表明GO对TRGO在富钙高碱环境下的分散有促进作用,且分散最佳质量比(%)为3∶10;与TRGO单掺相比,复掺GO能促进砂浆水化产物形成片状结构并互相交织,使得力学性能显著提升,当w(GO)∶w(TRGO)=0.3∶1.0时,28 d抗折强度和抗压强度与单掺TRGO相比提升了21.34%和34.52%,随着掺量增加力学性能反而下降;水泥砂浆的电导率随着GO与TRGO导电相的增加而增大,当w(GO)∶w(TRGO)=0.12∶0.4时,28 d龄期试件的电阻率呈现突变现象,表明该体系出现渗滤阈值;保持分散最佳比例下当TRGO大于0.7%(质量分数)之后,增加掺量对电阻率的影响趋于平缓且走低的趋势,表明TRGO掺量0.7%(质量分数)为试件电阻率的添加阈值。     

氧化石墨烯的还原程度对水泥砂浆复合材料性能的影响

该研究制备不同还原程度的还原氧化石墨烯(rGO),研究还原参数对水泥砂浆复合材料的抗折和抗压强度的影响.采用接触角测量仪(CA)、射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)和透射电镜(TEM)对材料结构进行测试和表征.结果表明,rGO的最佳还原参数为0.2?wt％水合肼和15?mi...     

Ni2CoS4/还原氧化石墨烯/多孔还原氧化石墨烯的制备及其在超级电容器中的应用

采用水热法制备Ni_2CoS_4活性材料,通过物理过程和水热反应将其与氧化石墨烯(GO)、水热多孔氧化石墨烯(HHGO)复合得到Ni_2CoS_4/还原氧化石墨烯/多孔还原氧化石墨烯(Ni_2CoS_4/RGO/HRGO)复合电极材料。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、循环伏安测试、恒流充放电测试和交流阻抗测试等,对复合材料的形貌结构、电化学性能进行了表征。研究结果表明:在1 A/g的电流密度下,其比电容为1 684 F/g,在5 A/g的电流密度下循环2 000次后,其比电容保持率为91.8%。Ni_2CoS_4/RGO/HRGO优良的电化学行为归因于这种复合结构使电解液对电极材料的润湿程度提高,进而提高了离子和电荷的传输速率,同时也缓解石墨烯、Ni_2CoS_4的团聚和循环过程中的体积变化。因此,Ni_2CoS_4/RGO/HRGO是一种有良好应用前景的高性能超级电容器电极材料。     

氧化石墨烯的化学还原研究进展

简要介绍了化学法还原氧化石墨烯的主要类型和机理,着重对比了几种常用化学还原法的还原效果,探讨了化学还原法的优缺点,包括还原能力、还原条件及还原机理等方面的内容.认为发挥多种还原剂或制备方法的优势,可以获得性能优异的石墨烯,最后展望了其未来的发展方向及其他潜在应用.     

L-半胱氨酸还原氧化石墨烯的研究

采用改进Hummers法合成氧化石墨,在水中超声分散获得氧化石墨烯水溶胶,并加入L-半胱氨酸于95℃进行回流反应后得到还原氧化石墨烯。采用X射线衍射仪、傅里叶变换红外光谱仪和热重-差热扫描仪等探讨氧化石墨烯还原前后的结构与性能变化。结果表明,L-半胱氨酸能有效还原氧化石墨烯,且还原后的氧化石墨烯在乙醇中有较好的分散性,其所制薄膜的导电率为500S/m。由此法制备的石墨烯有望广泛应用于电子、光电、电容器和传感器等器件中。     

Tailor made exfoliated reduced graphene oxide nanosheets based on oxidative-exfoliation approach

This study presents a versatile and scalable strategy of ‘oxidation controlled exfoliation’ of rGO nanosheets synthesized from both Hummers and modified Hummers method. A co-relation between degree of oxidation of graphite oxide (GO) sheets and exfoliation of resulting synthesized rGO nanosheets has been successfully developed which in turn reflects in various properties of rGO sheets. The extent of exfoliation of rGO sheets has been well analyzed by XRD, SEM, BET and TEM techniques. Moreover, the quantitative analysis of degree of oxidation of GO has been estimated from FTIR spectra using quotient law method. The variations in number of rGO layers, defect density and sp² domain size have been investigated in detail by Raman spectroscopic technique. Both qualitative-quantitative analysis of rGO nanosheets have been discussed from their SAED pattern and HR-TEM images. The optical characterization of GO and corresponding rGO nanosheets has been studied in detail by UV- Vis spectroscopic technique.     

溶剂热法制备Fe_3O_4/氧化石墨烯复合材料及其性能研究

以氧化石墨和二茂铁为原料,采用溶剂热法原位一步合成了Fe3O4/还原氧化石墨烯(Fe3O4/RGO)复合物,通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)、振动样品磁强计(VSM)、循环伏安测试等手段对复合材料的形貌、结构、磁性能和电化学性能进行了表征。结果表明,该方法具有简单、可控的优点,通过调变前驱物中氧化石墨和二茂铁的比例,可以控制复合物中Fe3O4纳米粒子的负载量。所制备Fe3O4/RGO复合材料由平均粒径约20nm的Fe3O4纳米颗粒高度分散在还原氧化石墨烯片层上组成,具有较好的超顺磁性,电化学稳定性和良好的倍率性能。     

Ultrathin Co3O4 nanosheets highly dispersed on reduced graphene oxide: An efficient bi-functional catalyst for Li-O2 battery

Ultrathin Co₃O₄ nanosheets grown on the reduced graphene oxide (Co₃O₄/rGO) was synthesized by a simple hydrothermal method and was investigated as a cathode in a Li-O₂ battery. Benefited from the synergistic effect between Co₃O₄ and rGO, the hybrid exhibits a high initial capacity of 10,528 mAh g^?1 along with a high coulombic efficiency (84.4%) at 100 mA g^?1. In addition, the batteries show an enhanced cycling stability and after 113 cycles, the cut-off discharge voltage remains above 2.5 V. The outstanding performance is intimately related to the high surface area of rGO, which not only provide carbon skeleton for the uniform distribution of Co₃O₄ nanosheets but also facilitate the reversible formation and decomposition of insoluble Li₂O₂. The results of electrochemical tests confirm that the Co₃O₄/rGO hybrid is a promising candidate for the Li-O₂ batteries.     

High-performance asymmetric supercapacitors based on reduced graphene oxide/polyaniline composite electrodes with sandwich-like structure

The sandwich-like structure of reduced graphene oxide/polyaniline(RGO/PANI) hybrid electrode was prepared by electrochemical deposition. Both the voltage windows and electrolytes for electrochemical deposition of PANI and RGO were optimized. In the composites, PANI nanofibers were anchored on the surface of the RGO sheets, which avoids the re-stacking of neighboring sheets. The RGO/PANI composite electrode shows a high specific capacitance of 466 F/g at 2 m A/cm~2 than that of previously reported RGO/PANI composites. Asymmetric flexible supercapacitors applying RGO/PANI as positive electrode and carbon fiber cloth as negative electrode can be cycled reversibly in the high-voltage region of 0–1.6 V and displays intriguing performance with a maximum specific capacitance of 35.5 m F cm~(-2). Also, it delivers a high energy density of 45.5 m W h cm~(-2) at power density of 1250 m W cm~(-2). Furthermore, the asymmetric device exhibits an excellent long cycle life with 97.6% initial capacitance retention after 5000 cycles.Such composite electrode has a great potential for applications in flexible electronics, roll-up display,and wearable devices.     

A low-cost method for preliminary separation of reduced graphene oxide nanosheets

Reduced graphene oxide (RGO) nanosheets were produced by chemical reduction of exfoliated graphite oxide. Atomic force microscopy (AFM) images show that the obtained RGO nanosheets vary greatly in lateral-dimensional sizes, ranging from less than 100  100 nm to more than 2000  2000 nm. In order to separate these nanosheets, one simple and low-cost method mainly based on magnetic-stirring and centrifugation treatments was proposed. Preliminary statistical analysis of RGO nanosheets, based on AFM images, shows that the dot-like RGO nanosheets (with lateral dimensions less than 100  100 nm) and leaf-like RGO nanosheets (with lateral dimensions more than 500  500 nm) were effectively separated by this simple method.     

Facile and size-controllable preparation of graphene oxide nanosheets using high shear method and ultrasonic method

ABSTRACT

The lateral size of the graphene oxide (GO) nanosheets could be controlled by preparation method, and a simple and effective strategy to adjust the lateral size of GO nanosheets by selecting suitable method is presented. The high shear method was introduced to produce GO nanosheets, and the GO nanosheets (few micrometres) prepared by high shear method is about one order of magnitude larger than GO nanosheets (few hundred nanometres) obtained by ultrasonic method, as evidenced by atomic force microscopy. The FTIR, XPS and Raman analysis revealed that there are no distinct differences in composition and functional groups between the GO nanosheets produced by high shear method and ultrasonic method. The cavitation in the procedure of ultrasonic method is favourable for GO exfoliation, but it also could result in damage to GO nanosheets. The shearing force in the process of high shear method is effective for GO delamination with minimal fragmentation. The results indicated that the high shear method proposed in this paper is an efficient exfoliation means to produce single-layer GO nanosheets.     

爆炸法合成石墨烯

以石墨氧化物为前躯体,采用爆炸法合成石墨烯.利用XRD,SEM,XPS,TEM,SAED和Raman等测试手段对石墨烯的形貌,成份和结构进行表征.结果表明,石墨氧化物在爆炸产生的热量和冲击波的作用下发生完全剥离并被还原成石墨烯.新合成的石墨烯呈透明褶皱状,含有2层～5层石墨层,并具有较好的晶体结构.

Abstract：

Graphene nanosheets were synthesized using graphite oxide as a precursor by detonation. The composition,and structure of graphene nanosheets were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,scanning and transmission electron microscopy,selected area electron diffraction,and Raman spectroscopy. Results indicated that the as-prepared material was transparent and wrinkled,and comprised 2-5 graphenes with a highly crystalline structrue. The exfoliation and reduction of graphite oxide to graphene nanosheets was induced by the self-generated thermal energy and shockwave of detonation.     

Ambient flash sintering of reduced graphene oxide/zirconia composites:Role of reduced graphene oxide

Fabrication of graphene/ceramic composites commonly requires a high-temperature sintering step with long times as well as a vacuum or inert atmosphere,which not only results in property degradation but also significant equipment complexity and manufacturing costs.In this work,the ambient flash sintering behavior of reduced graphene oxide/3 mol% yttria-stabilized ZrO₂(rGO/3 YSZ) composites utilizing rGO as both a composite component and a conductive additive is reported.When the sintering condition is carefully optimized,a dense and conductive composite can be achieved at room temperature and in the air within 20 s.The role of the rGO in the FS of the rGO/3 YSZ composites is elucidated,especially with the assistance of a separate investigation on the thermal runaway behavior of the rGO.The work suggests a promising fabrication route for rGO/ceramic composites where the vacuum and furnace are not needed,which is of interest in terms of simplifying the fabrication equipment for energy and cost savings.     

石墨烯纳米片/环氧树脂复合材料的制备与介电性能研究

以天然鳞片石墨为原料,通过Hummers法制备氧化石墨,微波热解剥离制备出少层数的石墨烯纳米片。以硅烷偶联剂KH-560为改性剂,超声共混制备石墨烯纳米片/环氧树脂复合材料。采用FT-IR和SEM分析样品的微观结构和形貌,测试其介电性能。结果表明,随着石墨烯纳米片添加量的增加,复合材料介电常数呈现先增大后减小的趋势,当石墨烯纳米片含量为0.3%(质量分数)时,介电常数达到最大;石墨烯纳米片对复合材料介电损耗的影响与之相反;偶联改性使复合材料的介电常数增大,介电损耗减小。     

Spectroscopic studies of large sheets of graphene oxide and reduced graphene oxide monolayers prepared by Langmuir-Blodgett technique

Graphene oxide (GO) sheets prepared by chemical exfoliation were spread at the air-water interface and transferred to silicon substrates by Langmuir-Blodgett technique as closely spaced monolayers of 20-40 μm size. Hydrazine exposure followed by annealing in vacuum and argon ambient results in the formation of reduced graphene oxide (RGO) monolayers, without significantly affecting the overall morphology of the sheets. The monolayer character of both GO and RGO sheets was ascertained by atomic force microscopy. X-ray photoelectron spectroscopy supported by Fourier transform infrared spectroscopy revealed that the reduction process results in a significant decrease in oxygen functionalities, accompanied by a substantial decrease in the ratio of non-graphitic to graphitic (sp² bonded) carbon in the monolayers from 1.2 to 0.35. Raman spectra of GO and RGO monolayers have shown that during the reduction process, the G-band shifts by 8-12 cm^− 1 and the ratio of the intensities of D-band to G-band, I(D)/I(G) decreases from 1.3 ± 0.3 to 0.8 ± 0.2, which is in tune with the smaller non-graphitic carbon content of RGO monolayers. The significant decrease in I(D)/I(G) has been explained by assuming that substantial order is present in precursor GO monolayers as well as RGO monolayers obtained by solid state reduction.