石墨烯基TiO_2光催化剂的制备及其研究进展

石墨烯作为一种新型二维碳质纳米材料,与TiO_2复合可制得石墨烯基TiO_2光催化材料。介绍了石墨烯的结构与性质,概述了石墨烯及石墨烯基TiO_2光催化剂的制备方法,并总结了石墨烯基TiO_2复合材料在光催化分解水制氢、光催化还原CO_2、光催化降解有机污染物等领域的应用及未来的发展方向。     

石墨烯复合材料的应用进展

从石墨烯发现至今,人们开发出了多种多样的石墨烯复合材料并取得了一系列的研究进展,为石墨烯复合材料的进一步发展提供了技术、理论支持。本文综述了石墨烯基复合材料在超级电容器、电池、光催化材料、污染物处理、材料增强增韧、传感器等领域的应用现状,指出当前研究的不足之处,并指明石墨烯复合材料未来发展方向。     

石墨烯基异质结光催化复合材料的研究进展

石墨烯具有低成本、高电子迁移率、透光率、比表面积与稳定性的特点,近年来在光催化领域作为助催化剂研究广泛。随着研究人员对石墨烯性质的深入研究,基于不同电子结构设计不同石墨烯基异质光催化复合材料,正成为光催化领域所关注的热点,但各类异质结的设计较不明朗。基于异质结设计理论与石墨烯电子结构,本文主要综述了石墨烯基肖特基异质结、II型异质结、Z-Scheme异质结、面内异质结几种光催化复合材料的研究进展,总结了石墨烯基异质光催化复合材料的设计方法与存在的问题,讨论了基于第一性原理的计算理论在石墨烯基异质结光催化复合材料设计中的作用,并展望了未来的发展方向。     

硅藻土基光催化复合材料研究进展

介绍了硅藻土结构及物理和化学性质,综述了现阶段国内外通过溶胶-凝胶法、溶剂热法、液相沉积法制备硅藻土基光催化复合材料的研究进展;对硅藻土光催化机理、硅藻土金属氧化物复合催化机理及硅藻土石墨烯复合催化机理进行了介绍,并综述了硅藻土光催化复合材料在降解印染污染物、甲醛和处理重金属离子废水领域的应用,提出了硅藻土基光催化复合材料现阶段发展存在的问题与今后的研究方向。     

ZnO-石墨烯复合材料光催化降解污染物研究进展

Zn O-石墨烯纳米复合材料能促进电子-空穴的有效分离,有较大的表面积,有利于污染物和自由基的扩散和传质,电子可从Zn O的空穴高能导带直接转移到石墨烯,可提高复合材料在紫外或可见光下的光催化性能,因而Zn O-石墨烯纳米复合材料在光催化领域中被广泛研究。综述了Zn O-石墨烯纳米复合材料的制备,及其在光催化降解污染物应用中的最新研究进展。     

石墨烯/TiO_2复合材料光催化降解有机污染物的研究进展

石墨烯是一种新型的碳纳米材料,具有超大的比表面积和优良的导电性能,将石墨烯与TiO_2复合可显著提高复合材料的光催化性能,在光催化领域具有广泛的应用前景。主要介绍了石墨烯/TiO_2复合纳米材料的制备方法以及在光催化降解有机污染物方面的应用,并分析了石墨烯/TiO_2复合材料促进光催化机理,最后对石墨烯/TiO_2复合光催化剂未来的发展趋势提出了展望。     

石墨烯/TiO2复合材料光催化降解有机污染物的研究进展

石墨烯是一种新型的碳纳米材料,具有超大的比表面积和优良的导电性能,将石墨烯与TiO₂复合可显著提高复合材料的光催化性能,在光催化领域具有广泛的应用前景。主要介绍了石墨烯/TiO₂复合纳米材料的制备方法以及在光催化降解有机污染物方面的应用,并分析了石墨烯/TiO₂复合材料促进光催化机理,最后对石墨烯/TiO₂复合光催化剂未来的发展趋势提出了展望。     

超声一步制备CeO2/石墨烯复合材料及其高效光催化性能

本文采用超声法一步合成了CeO_2/石墨烯复合材料光催化剂。XRD分析表明,合成的样品中CeO_2为立方相,晶粒尺寸为5-10nm左右。TEM分析进一步证明合成的样品为CeO_2/石墨烯复合材料,且复合均匀。采用染料RHB为目标污染物进行光催化性能测试。结果表明,合成的纳米CeO_2/石墨烯复合材料光催化剂具有优异的光催化活性,在最佳负载条件下,能在5分钟之内达到90%的光催化降解效果。     

ZnSn(OH)_6/石墨烯复合材料的制备及其光催化性能的研究

采用水热法制备出Zn Sn(OH)6/石墨烯复合光催化材料,利用XRD、FT-IR、UV-vis DRS和BET对样品的结构和形貌进行了表征。以亚甲基蓝为模拟污染物考察了复合材料的光催化性能。结果表明,当石墨烯质量分数为3%时,Zn Sn(OH)6/石墨烯复合材料的光催化性能最优,紫外照射100 min后,对亚甲基蓝降解率达到98.1%,比纯Zn Sn(OH)6光催化活性提高了1.74倍。经过5次循环使用后依然有96.4%的降解率。Zn Sn(OH)6/石墨烯复合光催化材料对工业染料分散黄、活性红和酸性蓝也有很好的降解活性,说明Zn Sn(OH)6/石墨烯复合材料具有很好的普适性。     

石墨烯基催化剂的研究进展

近年来,二维石墨烯由于其独特的热、电和光学性能而引起极大的关注。理论上,石墨烯具有高的比表面积,使其非常适于用作许多材料的理想载体。石墨烯是非常受欢迎的纳米材料,研究人员利用石墨烯非凡的性质将其与不同材料进行复合得到性质各异的复合材料并应用于各个领域。本文阐述了石墨烯基复合材料在催化领域的研究进展概况,特别是在光催化和电催化领域,介绍了近三年石墨烯基复合材料在催化方面取得的成果,分析了其特性、制备方法及物质间的相互作用等因素对催化性能的影响。指出了石墨烯基复合材料目前在催化领域存在的问题及未来发展的方向,期望为石墨烯基材料在催化剂方面的应用提供参考。     

石墨烯在光催化水解制氢中的应用

由于石墨烯优异的电子结构和电子传输性能,使得其在光催化领域的研究得到了广泛的关注。本文简要介绍了最新以石墨烯为基础的复合光催化剂的制备方法及其在催化水分解制氢方面的应用,重点评述了石墨烯及其氧化物、TiO2与石墨烯类复合物、CdS与石墨烯类复合物、含氧金属酸盐与石墨烯类复合物等的光催化性能,简要说明了光敏化、贵金属负载、非金属掺杂等对复合物光催化性能的影响。最后,指出对于石墨烯与纳米材料复合物的结构及光催化作用的机理都有待于进一步的研究,以便充分利用石墨烯的二维平面结构制得具有较高光催化水解制氢活性的催化剂。     

Glucose sensing,photocatalytic and antibacterial properties of graphene–ZnO nanoparticle hybrids

A simple and efficient approach was developed to uniformly decorate graphene nanosheets with zinc oxide (ZnO) nanoparticles. A single source precursor, zinc benzoate dihydrazinate complex, has been used for the in situ generation of ZnO nanoparticles onto graphene at a relatively low temperature, 200 °C. Physico chemical analyses such as X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy revealed that ZnO nanoparticles were finely dispersed on the surface of graphene. ZnO–graphene hybrids were further characterized by Raman spectroscopy and ultraviolet visible spectroscopy and room-temperature photoluminescence. The materials exhibited excellent photocatalytic activity as evident from the degradation of methylene blue in ethanol under UV irradiation. An electrochemical glucose biosensor was fabricated by immobilization of glucose oxidase on the ZnO–graphene hybrids. This biosensor showed improved sensitivity towards glucose as compared to graphene. Also, the hybrids showed significant antibacterial activity against E. coli, gram negative bacteria. This simple and economical preparation strategy may be extended for the preparation of other graphene-based hybrids.     

Surfactant-free synthesis of homogeneous nano-grade cadmium sulfide grafted reduced graphene oxide composite as a high-activity photocatalyst in visible light

Zero-dimensional cadmium sulfide (CdS) nanoparticles with small size (∼50 nm) were grafted on the two-dimensional reduced graphene oxide (RGO) nanosheet via a facile hydrothermal method without any surfactant to synthesize CdS@RGO nanocomposites in this paper. The structural analysis confirms the strong attachment and interaction between CdS and RGO in CdS@RGO photocatalyst, which leads to a higher photocatalytic efficiency (95.3%) with superior anti-corrosion stability (almost no change of efficiency over three repeated experiments) to that of pure CdS in visible light. The unique hybrid nanostructure of CdS@RGO can effectively prevent the self-corrosion of CdS and facilitate the separation of electron-hole pairs. Consequently, these outstanding photocatalytic performances of CdS@RGO endow it with a promising prospect for the degradation of organic pollutants and this work can be extended to other graphene-based inorganic semiconductor composites.     

Innovative synthesis of a novel ZnO/ZnBi2O4/graphene ternary heterojunction nanocomposite photocatalyst in the presence of tragacanth mucilage as natural surfactant

Developing interfacial connections is one of the breakthrough strategies to improve the photocatalytic activity of graphene/p-n heterojunction systems. Herein, natural tragacanth mucilage, for the first time, was employed as cost-effective and ecofriendly surfactant to prepare highly efficient ZnO–ZnBi₂O₄/graphene hybrid photocatalyst. The results indicated that the methylene blue (MB) photocatalytic degradation efficiency of ZnO–ZnBi₂O₄/graphene-mucilage heterojunction, containing 10 wt% ZnBi₂O₄ and 1 wt% graphene, was ～1.2, 1.4, 3.1 and 8.3 times higher than that of ZnO–ZnBi₂O₄/graphene, ZnO–ZnBi₂O₄, ZnBi₂O₄ and ZnO samples, respectively. This significant improvement in the photocatalytic performance could be mainly ascribed to the desirable advantages of using natural mucilage as surfactant, including uniform distribution of ZnO–ZnBi₂O₄ nanoparticles on the surface of graphene sheets, increasing of the effective surface area, and improving of the charge carriers separation. Based on the trapping experiments, electron spin resonance and photoelectrochemical Mott-Schottky tests, direct Z-Scheme charge transfer mechanism with hydroxyl radicals as main active species was suggested for photocatalytic degradation of MB on the ZnO–ZnBi₂O₄/graphene-mucilage nanocomposite. This study provides a new insight to fabricate more homogeneous and close contact interfaces in graphene-based hybrid photocatalytic systems for environmental remediation.     

Graphene as initiator/catalyst in polymerization chemistry

One of the most important applications of graphene-based materials is the formation of nanocomposite materials, where graphene in the bulk-polymer matrix transfers its properties onto the polymeric material. Control of the polymer/graphene interface by attached polymeric interlayers is essential to generate nanocomposites, thus avoiding the aggregation of graphene nanoparticles. Among all graphene materials graphene oxide (GO) and reduced graphene oxide (r-GO) can be prepared on large scales useful for mass production graphene/polymer composites. The direct use of graphene materials as both, the polymerization initiator or catalyst and additive not only diminishes the agglomeration of particles in composites but also reduces the process of composite production to one facile step, which in turn avoids further purification regarding to strong acid initiators and metal particles catalysts. Here, literature activities within the past ∼10 years using graphene-based materials either as initiator or catalyst in different polymerization reactions are reviewed.     

The role of microwave absorption on formation of graphene from graphite oxide

By means of manipulating the oxygen content in graphite oxides (GO) and/or graphene-based materials, we demonstrate that the microwave absorption capacity of carbon materials is highly dependent on their chemical composition and structure. The increase of oxygen in GO remarkably decreases its microwave absorption capacity due to the size decrease of the π–π conjugated structure in these materials, and vice versa. It was revealed that graphene is an excellent microwave absorbent while GO with poor microwave absorption capacity, the unoxidized graphitic region “impurities” in GO act as the microwave absorbents to initiate the microwave-induced deoxygenation. The addition of a small amount graphene to GO leads to avalanche-like deoxygenation reaction of GO under microwave irradiation (MWI) and graphene formation, which was used for electrode materials in supercapacitors. The interaction between microwaves and graphene or graphene-based materials may be used for the fabrication of a variety of graphene-based nanocomposites with exceptional properties and a wealth of practical applications.     

Graphene-based membranes for molecular and ionic separations in aqueous environments

Graphene-based laminar materials open up to new applications for molecular and ionic separations in aqueous environments due to the atomic thickness,mechanical strength, chemical stability and other fantastic properties.Recent advances on controlling the structure and chemical functionality of graphene-based membranes can potentially lead to new classes of tools for desalination, dehydration, toxicant rejection, specific ionic separation and so on. The recent developments of graphene-based membranes prepared by using a concept to form interlayer space between graphene sheets and creating nanoscale or sub-nanoscale pores in a graphene lattice, together with their mass-transfer mechanisms and potential applications in aqueous environments are reviewed. A summary and outlook is further provided on the opportunities and challenges in this arising field. This article is expected to address the intricate details of mass transport through two distinct graphene-based membranes in aqueous environment and to optimize the fabrication of graphene-based membranes as a fascinating separation system for a wide range of applications.     

Surfactant-free synthesis of a novel octahedral ZnFe2O4/graphene composite with high adsorption and good photocatalytic activity for efficient treatment of dye wastewater

Recently, significant effort has been made toward the development of graphene-based visible-ligh-responsive photocatalysts and their application to dye wastewater treatment. Herein, a series of octahedral ZnFe₂O₄/graphene (ZnFe₂O₄-G) nanocomposites were synthesized using a one-pot solvothermal reaction without the need of a surfactant as novel bifunctional materials exhibiting both high adsorption and good visible-light-responsive photocatalyst properties. The crystal structure, morphology and photocatalytic degradation properties, as well as adsorption behavior, of the octahedral ZnFe₂O₄/graphene composites were investigated in detail. The adsorption capacity and UV–vis spectrometry results indicate that the dye removal efficiency over the samples followed the order of: methylene blue (MB) > rhodamine B (RhB) > methyl orange (MO). The ZnFe₂O₄-G materials exhited enhanced photocatalytic degradation properties for cationic dyes (MB and RhB) compared to those for the anionic dye (MO). In addition, the experimental results indicate that the ZnFe₂O₄-G materials can decompose H₂O₂ in the visible-light photocatalytic process to form hydroxyl radicals (•OH), which are mainly responsible for the photodegradation of the organic contaminants.     

Facile synthesis and enhanced field emission properties of Cu nanoparticles decorated graphene-based emitters

Cu nanoparticles (Cu NPs) were decorated on the surface of graphene films to form composite emitters. The graphene films were deposited by electrophoretic deposition and subsequently coated with Cu NPs via electrochemical reduction. The Cu NPs decorated graphene films exhibited lower turn-on field, lower threshold field and larger field enhancement factor compared with those of the pristine films. The Cu NPs decorated graphene films also showed good emission stability. The field emission properties of Cu NPs decorated graphene films were tunable through adjusting decoration time. This graphene-based composite could be used as a possible candidate for vacuum electron source.     

Graphene-based flexible and stretchable thin film transistors

Graphene has been attracting wide attention owing to its superb electronic, thermal and mechanical properties. These properties allow great applications in the next generation of optoelectronics, where flexibility and stretchability are essential. In this context, the recent development of graphene growth/transfer and its applications in field-effect transistors are involved. In particular, we provide a detailed review on the state-of-the-art of graphene-based flexible and stretchable thin film transistors. We address the principles of fabricating high-speed graphene analog transistors and the key issues of producing an array of graphene-based transistors on flexible and stretchable substrates. It provides a platform for future work to focus on understanding and realizing high-performance graphene-based transistors.