NiO nanosheets grown on graphene nanosheets as superior anode materials for Li-ion batteries

This paper reports a hydrothermal preparation of NiO-graphene sheet-on-sheet and nanoparticle-on-sheet nanostructures. The sheet-on-sheet nanocomposite showed highly reversible large capacities at a common current of 0.1 C and good rate capabilities. A large initial charge capacity of 1056 mAh/g was observed for the sheet-on-sheet composite at 0.1 C, which decreased by only 2.4% to 1031 mAh/g after 40 cycles of discharge and charge. This cycling performance is better than that of NiO nanosheets, graphene nanosheets, NiO-graphene nanoparticle-on-sheet, and previous carbon/carbon nanotube supported NiO composites. It is believed that the mechanical stability and electrical conductivity of NiO nanosheets are increased by graphene nanosheets (GNS), the aggregation or restacking of which to graphite platelets are, on the other hand, effectively prevented by NiO nanosheets.     

Mechanisms of dyes adsorption on titanium oxide– graphene oxide nanocomposites

Graphene oxides (GOs), synthesized with different oxidation degrees and associated with Titanium dioxide (TiO₂) nanoparticles show efficient adsorption processes for dye molecules in solution. The structural, morphology, electronic and optical features of the nanocomposites were investigated by dedicated methods. Water remediation was investigated through the adsorption efficiency of methylene blue (MB) dye as a function of the nanocomposites concentration from 1 to 5 g/L in solutions. While pristine TiO₂ showed a maximum removal of ∼44%, the incorporation of the GO ensures the fast and complete elimination of MB within 9 min. The ball milling process contributed to the increase in the number of defects and surface area in the nanocomposites, which was demonstrated by I_D/I_G ratios by Raman spectroscopy and surface areas by BET. Pseudo-second-order and mechanistic kinetic models were considered, and the performed analysis points out the relevance of the pseudo-second-order model to account for the adsorption kinetics. The Langmuir and Freundlich isotherm models were applied to the experimental data to find an adequate model to describe the adsorption equilibrium, as well as the intra-particle diffusion model during the different adsorption stages involved in the TiO₂/GO nanocomposites. The role of the oxidation degree of GO was clarified through their respective efficiency in the removal of the dyes.     

Effects of humic acid on copper adsorption onto few-layer reduced graphene oxide and few-layer graphene oxide

The effects of humic acid (HA) on copper (Cu(II)) adsorption onto few-layer reduced graphene oxide (FRGO) and few-layer graphene oxide (FGO) were investigated using a batch equilibration method, micro-Fourier transform infrared spectroscopy, and extended X-ray absorption fine structure spectroscopy (EXAFS). The results showed that HA was adsorbed on FRGO through π–π interaction. The adsorbed HA introduced O-containing functional groups and negative charges to FRGO surfaces, increasing Cu(II) adsorption through chemical complexation and electrostatic attraction. In contrast, HA was adsorbed onto FGO mainly through polar interactions, due to its rich O-containing functional groups. The adsorbed HA had little effect on Cu(II) adsorption onto FGO because the shielding effect of HA on Cu(II) adsorption was offset by newly introduced adsorption sites of HA on FGO. EXAFS results suggested that Cu(II) was adsorbed on FRGO and FGO mainly through the coordination with their O-containing functional groups. When HA was added at pH 4.0 and 6.0, more Cu(II) was adsorbed on HA-coated FRGO. At pH 8.0, a portion of Cu(II) in solution precipitated on FRGO surface, while the presence of HA led to the formation of FRGO-HA-Cu ternary surface complexes instead of Cu(II) precipitation.     

Carbon nanotubes grown in situ on graphene nanosheets as superior anodes for Li-ion batteries

Graphene and carbon nanotubes are intriguing alternative anode materials for lithium ion batteries. The prevention of graphene restacking and facilitation of lithium diffusion into CNTs with large aspect ratio are highly desirable for the performance enhancements including capacity, cycliability and rate capability. In this work, we demonstrated that a multilayered graphene-CNT hybrid nanostructure was able to hold such merits. GNS were separated and stabilized by CNTs grown in situ on GNS surface. The length of CNTs was found to be a key factor to the electrochemical performances. The GNS-CNT composite with the shortest CNT decoration displayed highly reversible capacities of 573 mAh g(-1) at a small current of 0.2C and 520 mAh g(-1) at a large current of 2C. The growth and lithium storage mechanism for graphene-CNT composite was also proposed.     

Reduced graphene oxide with superior cycling stability and rate capability for sodium storage

Sodium ion battery is a promising electrical energy storage system for sustainable energy storage applications due to the abundance of sodium resources and their low cost. In this communication, the electrochemical properties of sodium ion storage in reduced graphene oxide (RGO) were studied in an electrolyte consisting of 1 M NaClO₄ in propylene carbonate (PC). The experimental results show that the RGO anode allowed significant sodium ion insertion, leading to higher capacity at high current density compared to the previously reported results for carbon materials. This is due to the fact that RGO possesses higher electrical conductivity and is a more active host, with large interlayer distances and a disordered structure, enabling it to store a higher amount of Na ions. RGO anode exhibits high capacity combined with long-term cycling stability at high current densities, leading to reversible capacity as high as 174.3 mAh g⁻¹ at 0.2 C (40 mA g⁻¹), and even 93.3 mAh g⁻¹ at 1 C (200 mA g⁻¹) after 250 cycles. Furthermore, RGO could yield a high capacity of 141 mAh g⁻¹ at 0.2 C (40 mA g⁻¹) over 1000 cycles.     

Preparation of manganese monoxide@reduced graphene oxide nanocomposites with superior electrochemical performances for lithium-ion batteries

Manganese monoxide (MnO) nanowire@reduced graphene oxide (rGO) nanocomposites are synthesized using a simple hydrothermal method combined with a calcination process. The structural and morphological characterization of the composites indicates that the MnO nanowires homogeneously anchor on both sides of the cross-linked rGO. The nanocomposites exhibit a high surface area of 126.5?m² g^?1. When employed as an anode material for lithium-ion batteries, the nanocomposites exhibit a reversible capacity of 1195 mAh g^?1 at a current density of 0.1?A?g^?1, with a high charge-discharge efficiency of 99.2% after 150 cycles. The three-dimensional architecture of the present materials exhibits high porosity and electron conductivity, significantly shortening the diffusion path of lithium ions and accelerating their reaction with the electrolyte, which greatly improves the lithium-ion storage properties. These excellent electrochemical performances make the composite a promising electrode material for lithium-ion batteries.     

氧化铁/石墨烯原位复合物对铬酸钾吸附性能研究

采用共沉淀法制备Fe_3O_4磁性纳米颗粒以及通过原位生长法制备Fe_3O_4与氧化石墨烯的复合物,并加入十六烷基三甲基溴化铵形成共价键交联反应化合物。采用X射线衍射仪和透射电子显微镜表征样品的形貌与尺寸,并以铬酸钾为吸附对象,研究吸附温度、吸附时间和溶液p H值对Fe_3O_4吸附性能的影响。结果表明,椭圆形颗粒的Fe_3O_4尺寸约(10~15)nm,与氧化石墨烯复合后,分散性明显提高;在室温和p H=3.5条件下,以Fe_3O_4与氧化石墨烯的质量比2∶1复合物作为吸附剂对铬酸钾的吸附效果达到最佳,每克的吸附容量可达251 mg;复合物经过磁分离、反复吸附循环实验6次后,对铬酸钾的吸附率仅下降10个百分点。     

氧化程度对氧化石墨烯吸附亚甲基蓝性能的影响

基于改进Hummers法,调控氧化剂KMnO₄用量制备了不同含氧官能团含量的氧化石墨烯（GOs）。采用XRD、XPS、AFM和FTIR分析了KMnO₄用量对GOs的结构特征、含氧官能团类型及含量的影响,研究了氧化程度对GOs吸附亚甲基蓝（MB）性能的影响。结果表明：KMnO₄用量对GOs-n（n=2,3,4（的含氧官能团类型和含量有显著影响;MB最大饱和吸附量依次为728.44、965.63和807.29 mg·g^-1,与Langmuir模型单分子层饱和吸附量的标准差为3.6%、3.7%和4.2%,吸附动力学过程符合准二级动力学模型,R²> 0.99。以GOs结构层上去质子化的羟基（-C-O^-）和羧基（-COO^-）为主要活性位点与MB发生化学控速的单分子层放热吸附,吸附热在20~27 kJ·mol^-1之间;低氧化程度的GOs以离子交换吸附为主导,吸附性能与GOs结构中-C-O（H（和-COO（H（的总量呈正相关。随氧化程度加深,GOs结构中环氧基（C-O-C）和羰基（C═O）以氢键作用吸附MB对吸附量的影响凸显。     

氧化石墨烯生长钨基氧化物酸环境电催化析氢

以磷钨酸为钨源,单层氧化石墨烯(GO)为载体,引入碳纳米管(CNTs),通过一步水热法和在空气中煅烧制备了纳米异质结(WO3-rGO-CNTs).通过FTIR、XRD、XPS、TG、SEM、EDS、TEM和BET对其进行了表征,利用线性伏安法和循环伏安法对其进行了电催化析氢(HER)反应测试.结果表明,WO3晶体粒子均...     

活化氧化石墨烯的制备及对甲基橙的吸附

为了提高氧化石墨烯(GO)的比表面积和吸附性能,采用氢氧化钾对GO进行高温固相活化,制备出活化氧化石墨烯(GOKOH),并将其用于对水中阴离子染料甲基橙(MO)的吸附研究。结果表明,GOKOH的比表面积可达672.48 m2/g。GOKOH能在较宽的p H范围内实现对MO的高效去除,去除率高达94.87%,吸附平衡时间约为150 min。准一级和准二级动力学拟合的理论平衡吸附容量分别为549.87 mg/g和549.45 mg/g,Langmuir模型的饱和吸附容量为632.91 mg/g。该吸附过程受边界层扩散与颗粒内扩散两个步骤控制,符合二级动力学模型和Langmuir模型,并主要以化学吸附为主。     

Biodistribution of PEGylated graphene oxide nanoribbons and their application in cancer chemo-photothermal therapy

To use graphene oxide nanoribbons (GONRs) in combination with chemo-photothermal therapy, we modified GONRs with phospholipid-polyethylene glycol (PL-PEG) to prepare PEGylated GONRs (PL-PEG-GONRs), followed by investigation of the short-term in vivo biodistribution of ^99mTc-labeled PL-PEG-GONRs and their excretion in mice. The ^99mTc-labeled PL-PEG-GONRs demonstrated a unique biodistribution pattern of rapid accumulation in and excretion from the liver. Moreover, we determined that the PL-PEG-GNORs were excreted from the body through the renal route in urine, and we used hematological analysis to show that the PL-PEG-GNORs were not toxic in vivo. Furthermore, doxorubicin-loaded PL-PEG-GONRs had IC₅₀ values for chemo-photothermal therapy toward U87 glioma cells that were 6.7-fold lower than the IC₅₀ values in traditional chemotherapy. With these advantages, PL-PEG-GONRs could be used as drug nanocarriers to develop an efficient cancer-therapy strategy that would not only improve the efficacy of the therapy, but would also reduce the risk of side effects of the nanocarrier in the body.     

Improving the field emission of graphene by depositing zinc oxide nanorods on its surface

Zinc oxide (ZnO) nanorods were vertically grown on the surface of graphene sheets by chemical vapor deposition, and their use in a field emission device was demonstrated. In comparison with pristine graphene, the graphene/ZnO nanorod hybrid structure exhibited efficient field emission with low turn-on field, low threshold field, high emission spot density, high field enhancement factor and excellent emitting stability. It is proposed that the introduction of mid-density ZnO nanorods on the surface of graphene sheets can increase the number of emitters, enhance tunneling probability, and lead to optimized field emission for the hybrid emitters. The results showed that the field emission properties of graphene can be tailored by growing various ZnO nanostructures on its surface.     

Polymer brushes on graphene oxide for efficient adsorption of heavy metal ions from water

The pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface-initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g⁻¹ for Pb(II), 258.6 mg g⁻¹ for Ag(I), 192.2 mg g⁻¹ for Cu(II), and 167.9 mg g⁻¹ for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer brushes in water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48156.     

Sacrificial template-directed synthesis of mesoporous manganese oxide architectures with superior performance for organic dye adsorption

Mesoporous MgO architectures were successfully synthesized by the direct thermal transformation of the sacrificial oxalate template. The as-prepared mesoporous architectures were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption-desorption techniques. The MgO architectures showed extraordinary adsorption capacity and rapid adsorption rate for removal of Congo red (CR) from water. The maximum adsorption capacity of the MgO architectures toward CR reached 689.7 mg g(-1), much higher than most of the previously reported hierarchical adsorbents. The CR removal process was found to obey the Langmuir adsorption model and its kinetics followed pseudo-second-order rate equation. The superior adsorption performance of the mesoporous MgO architectures could be attributed to the unique mesoporous structure, high specific surface area as well as strong electrostatic interaction.     

ZIF-8负载海藻酸钠/氧化石墨烯基底用于吸附盐酸四环素

为了解决金属-有机骨架材料ZIF-8在水溶液中难以回收的问题，以海藻酸钠（SA）为基础材料，采用直接滴加法将SA和氧化石墨烯（GO）混合溶胶滴入Ca2+溶液中，交联形成SA/GO凝胶基底，再将ZIF-8原位生长在SA/GO基底上，制得SA/GO/ZIF-8复合吸附剂用于去除环境废水中盐酸四环素（TC）。XRD、TEM和SEM表征结果证明ZIF-8在SA/GO凝胶基底上均匀生长，且经计算得ZIF-8的负载率高达34.21%。当温度为25 ℃、pH=7及TC浓度为50 mg/L时，30 mg SA/GO/ZIF-8复合吸附剂对TC的平衡吸附容量可达125.37 mg/g。吸附动力学和等温线结果表明SA/GO/ZIF-8对TC的吸附过程受化学活性位点控制，属于活性位点均匀的单层吸附。在循环吸附6次后，SA/GO/ZIF-8复合吸附剂对TC的去除率仍在85%以上。这种易于分离和高负载ZIFs的SA/GO/ZIF-8复合吸附剂有望成为去除废水中抗生素的理想选择。     

氧化石墨烯生长钨基氧化物酸环境电催化析氢

为了解决商用铂碳电极在电催化析氢反应（HER）领域生产成本高、催化剂使用周期短等问题，利用磷钨酸提供钨源，以单层氧化石墨烯（GO）作为载体，引入利于电子传输轨道的碳纳米管（CNTs），通过一步水热法和空气中煅烧制备得到WO3-rGO-CNTs纳米异质结电催化剂。利用FT-IR、XRD、XPS、TG、SEM、EDAX、TEM和BET对WO3-rGO-CNTs的化学结构和物理形貌进行了表征。结果表明，在单层GO表面均匀生长WO3晶体，并引入CNTs后，纳米异质结WO3-rGO-CNTs在酸性电解质中表现出优异的HER催化活性。利用线性伏安法（LSV）和循环伏安法（CV）对WO3-rGO-CNTs进行HER测试，当电流密度为10 mA/cm2时，其过电势为218 mV；塔菲尔斜率为130.5 mV/dec。当过电势为-0.5 V vs. RHE时，其阻抗值为8.2 Ω。同时，WO3-rGO-CNTs纳米异质结可以在218 mV（电流密度为10 mA/cm2）过电势下，保持50 h的稳定性和耐久性；其双层电容值为1.2 mF/cm2。电化学数据表明，WO3与GO和CNTs间由于异质结构的存在，产生了协同效应：GO为WO3晶体提供了广阔的金属反应活性位点，而CNTs则提供了利于电子传输的活性轨道。     

Synthesis of NiMoO4 nanorods on graphene and superior electrochemical performance of the resulting ternary based composites

NiMoO₄ nanorods have been directly synthesised on graphene sheet using a facile solvothermal method with subsequent calcination treatment. As an electrode for electrochemical capacitors, the graphene-NiMoO₄ composite electrode prepared at a mass ratio of 1:8 exhibited a specific capacitance of 670 F/g at 0.3 A/g and good rate capability. When cycled at 0.5 A/g for 3000 cycles, it retained 88% of its initial capacitance with a Coulombic efficiency of ~ 80%. This study presents a pungent and environmental benign research strategy for the development of graphene-NiMoO₄ ternary based electrochemical capacitors.     

氧化石墨烯吸附不同离子型染料对比研究

采用优化的Hummers法制备氧化石墨烯(GO),选取碱性紫5BN、阳离子红GTL、酸性橙8和直接红23这4种商业染料模拟染料废水,通过吸附剂用量和溶液pH值等因素研究GO对不同离子型染料的脱色效果.FT-IR和XRD表征显示该方法制备的GO结构中存在大量含氧基团,层间距明显扩大,从0.348 nm增加至0.876 n...