Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur(Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice.One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide(CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and-50°C. The synthesized laminar CC-rGO composite is mixed with acetylene black(AB) and coated on a commercial polypropylene(PP) membrane, resulting in a separator(CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Three-dimensional MoS_2/reduced graphene oxide aerogel as a macroscopic visible-light photocatalyst

Photocatalysis is regarded as an ideal technology for solving the urgent environmental and energy issues that we face today.Among the reported photocatalysts,molybdenum disulfide（MoS2） is very promising for applications in hydrogen production and pollutant photodegradation.However,its lack of active sites and the difficulty of recovering catalysts in powder form have hindered its wide application.Here,we report the successful preparation of a macroscopic visible-light responsive MoS2/reduced graphene oxide（MoS2/RGO） aerogel.The obtained MoS2/RGO aerogel exhibits enhanced photocatalytic activity towards hydrogen production and photoreduction of Cr（Ⅵ） in comparison with the MoS2 powder.In addition,the low density（56.1 mg/cm^3） of the MoS2/RGO aerogel enables it to be used as an efficient adsorption material for organic pollutants.Our results demonstrate that this very promising multifunctional aerogel has potential applications in environmental remediation and clean energy production.

Enabling High-Performance Sodium Battery Anodes by Complete Reduction of Graphene Oxide and Cooperative In-Situ Crystallization of Ultrafine SnO_(2)Nanocrystals

The main bottleneck against industrial utilization of sodium ion batteries(SIBs)is the lack of high-capacity electrodes to rival those of the benchmark lithium ion batteries(LIBs).Here in this work,we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few-layer graphene sheets loaded with ultrafine SnO_(2)nanocrystals,using short exposure of microwave to xerogel of graphene oxide(GO)and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO(RGO).The resultant nanocomposites(SnO_(2)@MWG)enabled significantly quickened redox processes as SIB anode,which led to remarkable full anode-specific capacity reaching 538 mAh g^(−1)at 0.05 A g^(−1)(about 1.45 times of the theoretical capacity of graphite for the LIB),in addition to outstanding rate performance over prolonged charge–discharge cycling.Anodes based on the optimized SnO_(2)@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g^(−1),and capacity retention of over 70.4%was maintained at a high areal loading of 3.4 mg cm^(−2),highly desirable for high energy density SIBs to rival the current benchmark LIBs.

Enhanced cycle performance of Li/S battery with the reduced graphene oxide/activated carbon functional interlayer

The high-energy lithium/sulfur(Li/S) battery has become a very popular topic of research in recent years due to its high theoretical capacity of 1672 m Ah/g. However, the polysulfide shuttle effect remains of great concern with a great number of publications dedicated to its mitigation. In this contribution, a three-dimensional(3D) reduced graphene oxide/activated carbon(RGO/AC) film, synthesized by a simple hydrothermal method and convenient mechanical pressing, is sandwiched between the separator and the sulfur-based cathode, acting as a functional interlayer to capture and trap polysulfide species. Consequently, the Li/S cell with this interlayer shows an impressive initial discharge capacity of 1078 m Ah/g and a reversible capacity of 655 m Ah/g even after 100 cycles. The RGO/AC interlayer impedes the movement of polysulfide while providing unimpeded channels for lithium ion mass transfer. Therefore, the RGO/AC interlayer with a well-designed structure represents strong potential for high-performance Li/S batteries.

Structural and optical properties of thermally reduced graphene oxide for energy devices

Natural intercalation of the graphite oxide, obtained as a product of Hummer＇s method, via ultra-sonication of water dispersed graphite oxide has been carried out to obtain graphene oxide（GO） and thermally reduced graphene oxide（RGO）.Here we report the effect of metallic nitrate on the oxidation properties of graphite and then formation of metallic oxide（MO） composites with GO and RGO for the first time. We observed a change in the efficiency of the oxidation process as we replaced the conventionally used sodium nitrate with that of nickel nitrate Ni（NO_3）_2, cadmium nitrate Cd（NO_3）_2,and zinc nitrate Zn（NO_3）_2. The structural properties were investigated by x-ray diffraction and observed the successful formation of composite of MO–GO and MO–RGO（M = Zn, Cd, Ni）. We sought to study the effect on the oxidation process through optical characterization via UV-Vis spectroscopy and Fourier Transform Infrared（FTIR） spectroscopy.Moreover, Thermo Gravimetric Analysis（TGA） was carried out to confirm 〉 90% weight loss in each process thus proving the reliability of the oxidation cycles. We have found that the nature of the oxidation process of graphite powder and its optical and electrochemical characteristics can be tuned by replacing the sodium nitrate（NaNO_3） by other metallic nitrates as Cd（NO_3）_2, Ni（NO_3）_2, and Zn（NO_3）_2. On the basis of obtained results, the synthesized GO and RGO may be expected as a promising material in antibacterial activity and in electrodes fabrication for energy devices such as solar cell, fuel cell,and super capacitors.

Synergistic Effects of Carbon Nanotube(CNT)and Reduced Graphene Oxide(RGO)on Mechanical and Thermal Properties of ZK61 Alloy

The hybrid of carbon nanotube(CNT)and reduced graphene oxide(RGO)reinforced ZK61 composite was fabricated by a hot extrusion process.Compared with the raw ZK61 alloy and single-reinforced composites,the hybrid-reinforced by RGO+CNT complex exhibited significant enhancements both in mechanical and thermal performance.By adjusting the proportion of RGO and CNT in ZK61 alloy,the obtained optimum ZK61/(0.06 wt%RGO+0.54 wt%CNT)composite exhibited increase of 25.4%in yield strength,26.5%in ultimate tensile strength,104%in failure strain and 30.4%in thermal conductivity,respectively,in comparison with ZK61 alloy.The superior properties of the nano-hybrid composite are attributed to the synergetic effects of RGO and CNT,leading to a uniform dispersion and integrated structure as well as the enhanced interfacial bonding with matrix.The strengthening ability of RGO and CNT was calculated to quantify their individual contribution to the improvement in mechanical and thermal properties of the ZK61 matrix composite.The RGO+CNT hybrids provide a promising way to develop Mg matrix composites with impressive performances.

Highly aligned reduced graphene oxide in alumina composites for strengthening,toughening,and electromagnetic interference shielding

Engineering ceramics with high strength,toughness and electromagnetic interference(EMI)shielding effectiveness(SE)are highly desirable as electromagnetic protecting material in harsh environment.Herein,we show that both excellent mechanical and EMI shielding performance can be realized in alumina composites embedded with highly aligned reduced graphene oxide(RGO),which are readily prepared via sintering of core-shell structured RGO@Al_(2)O_(3)nanoplates with pressure.Compared to monolithic Al_(2)O_(3),the highly aligned RGO/Al_(2)O_(3)composites show simultaneously improved strength and toughness up to~26.1%and~60.2%,respectively.The steeply rising R-curve behavior proves the better crack tolerance in the highly aligned structure with respect to randomly oriented one.Moreover,the RGO/Al_(2)O_(3)composites also exhibit a high specific EMI SE reaching~34 dB/mm in K band,due to the reflection and highly enhanced absorption after percolation in the out-of-plane direction.These findings provide a novel strategy of designing mechanically reliable engineering ceramic for EMI shielding.

Increased utilization and mass activity of PtRu on reduced graphene oxide by heat treatment of its aerogel followed by composite with nanomaterials

The method to increase PtRu utilization and its catalytic activity of PtRu nanoparticles supported on reduced graphene oxide(RGO)by avoiding its restacking was proposed with the aim of developing an active catalyst for a direct methanol fuel cell.The heat treatment at 200◦C of the GO aerogel(GOA)prepared by freeze drying of GO ice was introduced to weaken the attractive force of the hydrogen bonding between the GO sheets followed by the composite with the nanoparticles,i.e.,ketjenblack(KB),TiO_(2)and Ti_(4)O_(7),at different weight ratios.The catalyst supported on the heat-treated GOA(RGOA),PtRu/RGOA,improved the PtRu utilization to some extent and also increased the ECSA and mass activity compared to that of PtRu/RGO.RGOA had fewer oxygen functional groups,especially the epoxy groups.Due to the treatment and composite,the PtRu utilization was increased from 66.5%for PtRu/RGO to 128.6%for PtRu/RGOA+Ti_(4)O_(7)(4:1)and the mass activity was improved from 50.7 A/g-PtRu for PtRu/RGO to 130.5 A/g-PtRu for PtRu/RGOA+Ti_(4)O_(7)(1:1).The Ti_(4)O_(7)nanoparticles showed the best catalytic performance for the composite suggesting that the strong interaction between Ti_(4)O_(7)and the Pt nanoparticles was effective due to its high electronic conductivity.

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 ZrO_(2)(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.

Synthesis of hydrophobic carbon nanotubes/reduced graphene oxide composite films by flash light irradiation

Carbon nanotubes/graphene composites have superior mechanical, electrical and electrochemistry prop- erties with carbon nanotubes as a hydrophobicity boosting agent. Their extraordinary hydrophobic performance is highly suitable for electrode applications in lithium ion batteries and supercapacitors which often employ organic electrolytes. Also the hydrophobic features enable the oil enrichment for the crude oil separation from seawater. The ever reported synthesis routes towards such a composite either involve complicated multi-step reactions, e.g., chemical vapor depositions, or lead to insufficient extru- sion of carbon nanotubes in the chemical reductions of graphene oxide, e.g., fully embedding between the compact graphene oxide sheets. As a consequence, the formation of standalone carbon nanotubes over graphene sheets remains of high interests. Herein we use the facile flash light irradiation method to induce the reduction of graphene oxides in the presence of carbon nanotubes. Photographs, micrographs, X-ray diffraction, infrared spectroscopy and thermogravimetric analysis all indicate that graphene oxides has been reduced. And the contact angle tests confirm the excellent hydrophobic perfor- mances of the synthesized carbon nanotube/reduced graphene oxide composite films. This one-step treatment represents a straightforward and high efficiency way for the reduction of carbon nanotubes/graphene oxides composites.

A review article based on composite graphene@tungsten oxide thin films for various applications

Graphene and its derivatives are the hot topics of research during this decade due to their excellent thermal conductivities,mechanical strength,current densities,electron motilities,and large surface area.This review article explores the outstanding applicability and features of graphene derivatives.The transition metal oxides(TMOs)have also gained considerable research attention due to their unique physicochemical properties in photocatalytic,self-cleaning,and gas sensing applications.Among TMOs,tungsten metal oxides have received a tremendous response as they are naturally abundant,low in cost,less toxic,environmental friendly,and can be manufactured using various physical and chemical methods.It exhibits a cubic perovskite-like structure based on the corner-sharing of regular octahedra with the oxygen atoms at the corner and the tungsten atoms at the centre of each octahedron.It also shows structural polymorphism and sub stoichiometric phase transitions,which attracted the attention of researchers over the past few years to explore their potential in various applications.Pairing graphene and its derivatives with tungsten oxide(WO_(3))to create heterojunction could be an auspicious tool to improve photocatalysis,energy storage,medical,electrochromism,and energy efficiency conversion.In addition,composite exhibits significantly higher efficiency than either individual material due to their well-matched band edge positions,efficient charge separation,and light-harvesting abilities.The morphology and heterojunction were found to be quite beneficial in improving the overall performance of the composite.In this review article,the noteworthy endeavors and turning points are accomplished utilizing heterojunction between WO_(3)and graphene derivatives for different applications.This review article will also provide the research gap and excite new ideas for further improvement of graphene-based tungsten oxide nanocomposites.Conclusively,the scope of future research work to design the ternary composite with high efficiency utilizing WO_(3)and graphene is also explored.

Synthesis of iron oxide cubes/reduced graphene oxide composite and its enhanced lithium storage performance

Fe_(3)O_(4) is considered as a promising electrode material for lithium-ion batteries(LIBs) due to its low cost and high theoretical capacity(928 mAh/g).Nevertheless,the huge volume expansion and poor conductivity seriously hamper its practical applications.In this study,we use a facile hydrothermal reaction together with a post heat treatment to construct the three-dimensional heterostructured composite(Fe_(3)O_(4)/rGO) inwhich reduced graphene oxide sheets wraped the Fe_(3)O_(4) submicron cubes as the conductive network.The electric conduction and electrode kinetics of lithium ion insertion/extraction reaction of the composite is enhanced due to the assist of conductive rGO,and thus the Listorage performance is obviously improved.The composite exhibits a reversible charge capacity of772.1 mAh/g at the current density of 0.1 A/g,and the capacity retention reaches 70.3% after400 cycles at0.5 A/g,demonstrating obviously higher specific capacity and rate capability over the Fe_(3)O_(4) submicron cubes without rGO,and much superior cycling stability to the parent Fe_2 O_3 submicron cubes without rGO.On the other hand,as a synergic conductive carbon support,the flexible rGO plays an important role in buffering the large volume change during the repeated discharge/charge cycling.

Flexible and disposable paper-based gas sensor using reduced graphene oxide/chitosan composite

Nitrogen dioxide(NO_(2))is a representative toxicant in air pollution that mostly arises from the exhaust gas released by automobiles.It is related to various respiratory diseases such as pneumonia and sudden infant death syndrome.Additionally,because the toxicity of nitrogen dioxide is high in overpopulated areas(i.e.,a capital or metropolis),the development of simple,practical,and facile sensors is highly needed.This work presents a flexible and disposable paper-based NO_(2)sensor based on a reduced graphene oxide/chitosan(r GO/CS)composite.The synthesized r GO/CS composite can be easily flexed and deformed into various shapes,which are attributed to chitosan molecules that function as a dispersion and reduction agent and support material.In addition,this composite can be attached to paper owing to its adhesive property;hence it can be utilized in versatile applications in a disposable manner.By analyzing the conductive change of the r GO/CS composite when it reacts with NO_(2),we can detect nitrogen dioxide in a concentration range of 0–100 ppm with a detection limit of 1 ppm.Moreover,we performed NO_(2)detection in the exhaust gas released by automobiles using the r GO/CS composite for practical application.The results indicated that the r GO/CS composite has the potential to be used in feasible gas sensing as a facile and disposable sensor under various conditions.

Efficient removal of chlorophenols from water with a magnetic reduced graphene oxide composite

A magnetic reduced graphene oxide composite(MRGO) was successfully prepared by a simple and green method. MRGO was then used as an adsorbent and found to exhibit enhanced removal efficiency for various chlorophenols(CPs) from water compared with its precursors, graphene oxide(GO) and reduced graphene oxide. The CPs were o-chlorophenol, p-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Among them, 2,4,6-trichlorophenol, which exhibited the lowest water solubility and highest molecular weight, most easily bound to MRGO. The preferential interactions between MRGO and CPs were hydrophobic interactions(?-? stacking and hydrophobic effect). This result was confirmed by the equilibrium adsorption behavior in which isotherms were all well described by Freudlich model, indicating heterogeneous and multilayer adsorption. Therefore, CP adsorption was more favored under neutral and acidic conditions, and the decreased removal efficiency of MRGO at higher p H levels was due to the improved hydrophilicity of CPs for deprotonation effect. Moreover, MRGO showed fast removal of each CP, achieving adsorption equilibrium within 10.0 min, presented efficient separation from water under an external magnetic field, and was easily regenerated using dilute Na OH aqueous solution after reaching saturated adsorption. Adsorption capacity of the regenerated MRGO had almost no loss until after five cycles. In summary, MRGO was an efficient adsorbent for the removal of various CPs and had considerable application potential in water treatment.

Reduced Graphene Oxide/Carbon Fiber Composite Membrane for Self-floating Solar-thermal Steam Production

Solar-thermal water evaporation has attracted increasing attention owing to the promising potential to solve the global clean water and energy crisis.But,the development of this strategy is limited by the lack of materials with high solar-thernal conversion efficiency,local heating of superficial water,easy preparation and low cost.Herein,we proposed a facile strategy to prepare a reduced graphene oxide/carbon fiber composite membrane,denoted as RGO/CF membrane.The surface of the RGO/CF membrane was highly hydrophobic,endowing the composite membrane with the self-floating ability on the water without any assistance.The light absorbance ability achieved as high as ca.98%in the wavelength range of 300-1200 nm.The steam evaporation efliciency under the illumination of3-sun was 97%,generating water steam at a rate of 4.54 kg·m^-2·h^-1.Moreover,the solar-thermal steam production rate showed high stability during successive 30 cvcle tests.

Hybrid CuO-Co_(3)O_(4)nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries

Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully applied as enhanced anodes for lithium-ion batteries(LIBs).The CuO-Co_(3)O_(4)-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^(-1)after 200 cycles’cycling at 100 mA·g^(-1)with a capacity retention of 79%.The CuO-Co_(3)O_(4)-RGO compounds show superior electrochemical properties than the comparative CuO-Co_(3)O_(4),Co_(3)O_(4)and CuO anodes,which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages;the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co_(3)O_(4) nanospheres;the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.

PEO/rGO复合电热膜的制备及电热性能研究

采用导电性能优异的还原氧化石墨烯(rGO)为导电填料,以高分子聚合物聚氧化乙烯(PEO)为粘结剂,以N-甲基-2-吡咯烷酮(NMP)为溶剂配制成导电浆料,通过刮涂法高温固化得到聚氧化乙烯/还原氧化石墨烯(PEO/rGO)复合电热膜。通过X射线衍射仪、扫描电子显微镜、傅里叶变换红外光谱仪对复合电热膜进行分析表征,并测试了其电学特性和电加热性能。结果表明:PEO/rGO复合电热膜的方阻随着rGO含量的增加而逐渐下降,且方阻的下降速度由快到慢;PEO/rGO复合电热膜的升温速度随着导电填料rGO含量的增加逐渐变缓;当rGO含量较多、PEO含量较少时,会造成升温速率下降,也会造成电热平台不稳定;当rGO质量分数为20%时,在施加18V直流电压下复合电热膜可快速升温至43℃,并且表现出平稳的电热平台和较高的电加热效率,能够满足低温高效率复合电热膜的使用要求。

TiO_(2)/石墨烯基复合材料的制备及光催化降解染料研究

采用改进Hummers法制备氧化石墨烯(GO)和水解法制备的TiO_(2)及溶剂热法制备了还原氧化石墨烯(rGO)和一系列不同浓度的rGO/TiO_(2)纳米复合材料(0、5%、10%、15%、20%质量分数),并对合成产物进行SEM、XRD、XPS、DRS、Raman等表征,研究不同实验条件下纯TiO_(2)和rGO/TiO_(2)复合催化剂对亚甲基蓝染液(MB)的降解效果。结果表明,复合光催化剂中TiO_(2)主要为锐钛矿相,溶剂热合成引入的还原氧化石墨烯(rGO)对TiO_(2)的物相没有产生影响,rGO的引入使得rGO/TiO_(2)吸收带发生一定红移,TiO_(2)禁带宽度由3.23降低至3.09 eV;合成的(15%质量分数)rGO/TiO_(2)具有最佳的光催化效果,光催化活性最高,在100 W高压汞灯照射下70 min对20 mg/L的亚甲基蓝染料的降解率达97.6%;在500 W氙灯光源下照射70 min对20 mg/L亚甲基蓝染料的降解率达到93.2%,(15%质量分数)rGO/TiO_(2)复合光催化剂具有良好的光催化降解性及循环稳定性,5次循环光催化降解后,rGO/TiO_(2)有86.1%的降解效率。表现出了优异的吸附和光催化性能,这可为光催化处理废液提供了一种有效的方法。

磁性CoFe/Ni_(4)Zn/FeO/rGO复合材料的制备及电磁波吸收性能

创新的微观结构设计和合适的多组分策略对于具有强吸收和宽有效吸收带宽(EAB)的先进电磁吸波材料(EAM)仍然具有挑战性。采用简单的水热还原与高温煅烧制备了磁性CoFe/Ni_(4)Zn/FeO/还原氧化石墨烯(rGO)(MR)复合吸波材料,MR复合材料具有丰富的异质界面与多孔结构,通过引入磁性颗粒调节电磁参数、提高阻抗匹配和衰减能力,在12.88GHz时最小反射损耗可以达到-46.15dB,有效吸收带宽高达约6.1GHz(10.64~16.72GHz)。MR复合材料优异的电磁吸波性能归因于三维多孔结构的多重反射、散射和弛豫过程以及界面基质的强界面极化。磁/介电性的多组分复合材料MR具备多种损耗机制,其协同作用能够进一步增强材料的吸波性能。

用于钎焊C/C复合材料的稀土改性还原氧化石墨烯增强AgCuTi复合钎料

为了解决钎焊接头中脆性化合物的形成问题,我们设计了一种创新性的稀土改性还原氧化石墨烯增强AgCuTi复合钎料,进而获得了以Ag-Cu共晶为主要组织且脆性化合物生成量合适的钎焊接头。对比分析了有无稀土Ce改性的复合钎料的成分和显微组织,结果表明,经Ce改性后的还原氧化石墨烯在钎料中更加均匀分散。比较了分别采用有无Ce改性的钎料钎焊C/C复合材料-C/C复合材料接头的界面微观结构,并研究了石墨烯含量对接头组织和性能的影响。结果表明,由于经Ce改性的钎料中的还原氧化石墨烯分散性更好,从而细化了焊缝组织,且物相分布更均匀,使得接头的剪切强度明显提高。当石墨烯含量为0.5 wt.%时,使用Ce改性的钎料所得钎焊接头的平均剪切强度最高,为31.82 MPa,提高了50%。