N-doped graphene quantum dot-decorated N-TiO2/P-doped porous hollow g-C_(3)N_(4) nanotube composite photocatalysts for antibiotic photodegradation and H2 production

Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

La内嵌graphene/MoS_(2)层的储氢性能研究

运用密度泛函理论研究了La内嵌graphene/MoS_(2)层的储氢性能.由于La的内嵌graphene/MoS_(2)异质结的层间距被拉大.详细研究了氢气分子在La内嵌的graphene/MoS_(2)结构上的吸附行为.结果表明,一个La原子最多可以吸附六个氢气分子,采用GGA/PBE泛函计算得到氢气分子的平均吸附能为0.198 eV.合适的吸附能使得设计材料能够在温和条件下实现可逆存储.重要的是,La原子能够分散地内嵌在graphene/MoS_(2)异质结中,这将为氢气分子提供更多吸附位.研究表明理论上预测La内嵌graphene/MoS_(2)材料是一种潜在的储氢材料.

Hierarchical Reduced Graphene Oxide-MnO_(2)@Polypyrrole Coaxial Nanotube Composite Hydrogel as a Potential Adsorbent for Cr(Ⅵ)Removal

A hierarchical reduced graphene oxide-MnO_(2)@polypyrrole coaxial nanotube composite hydrogel was prepared via oxidative polymerization of pyrrole in the presence of MnO_(2)nanotubes,followed by the hydrothermal treatment of graphene oxide and MnO_(2)@polypyrrole coaxial nanotubes.The stable composite hydrogel with a hierarchical network was composed of one-dimensional MnO_(2)@polypyrrole coaxial nanotube and two-dimensional graphene nanosheet and characterized by scanning electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,Brunauer-Emmett-Teller surface,and X-ray photoelectron spectroscopy measurements.The composite hydrogel can be used as an efficient adsorbent for Cr(Ⅵ)removal due to the synergistic interaction between graphene and MnO_(2)@polypyrrole and the hierarchical structure of the hydrogel.Moreover,the composite hydrogel is easily separated because of its stable monolith,and it is reusable(76.8%of removal ability remaining after five adsorption-desorption cycles).The simple fabrication and cost-effective separation process together with the excellent absorption performance endow the composite hydrogel with great potential for practical wastewater treatment.

Regulation of interlayer channels of graphene oxide nanosheets in ultra-thin Pebax mixed-matrix membranes for CO_(2) capture

For the application of carbon capture by membrane process,it is crucial to develop a highly permeable CO_(2)-selective membrane.In this work,we reported an ultra-thin polyether-block-amide(Pebax)mixedmatrix membranes(MMMs)incorporated by graphene oxide(GO),in which the interlayer channels were regulated to optimize the CO_(2)/N_(2) separation performance.Various membrane preparation conditions were systematically investigated on the influence of the membrane structure and separation performance,including the lateral size of GO nanosheets,GO loading,thermal reduction temperature,and time.The results demonstrated that the precisely regulated interlayer channel of GO nanosheets can rapidly provide CO_(2)-selective transport channels due to the synergetic effects of size sieving and preferential adsorption.The GO/Pebax ultra-thin MMMs exhibited CO_(2)/N_(2) selectivity of 72 and CO_(2) permeance of 400 GPU(1 GPU=106 cm^(3)(STP)·cm^(2)·s^(-1)·cmHg^(-1)),providing a promising candidate for CO_(2) capture.

Fabrication of a novel electrochemical sensor based on MnFe_(2)O_(4)/graphene modified glassy carbon electrode for the sensitive detection of bisphenol A

Manganese ferrite(MnFe_(2)O_(4))has the advantages of simple preparation,high resistivity,and high crystal symmetry.Herein,we have developed an electrochemical sensor utilizing graphene and MnFe_(2)O_(4) nanocomposites modified glassy carbon electrode(GCE),which is very efficient and sensitive to detect bisphenol A(BPA).MnFe_(2)O_(4)/graphene(GR)was synthesized by immobilizing the MnFe_(2)O_(4) microspheres on the graphene nanosheets via a simple one-pot solvothermal method.The morphology and structure of the MnFe_(2)O_(4)/GR nanocomposite have been characterized through scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).In addition,electrochemical properties of the modified materials are comparably explored by means of cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and differential pulse voltammetry(DPV).Under the optimal conditions,the proposed electrochemical sensor for the detection of BPA has a linear range of 0.8-400μmol/L and a detection limit of 0.0235μmol/L(S/N=3)with high sensitivity,good selectivity and high stability.In addition,the proposed sensor was used to measure the content of BPA in real water samples with a recovery rate of 97.94%-104.56%.At present,the synthesis of MnFe_(2)O_(4)/GR provides more opportunities for the electrochemical detection of BPA in practical applications.

基于石墨烯/WS_(2)可饱和吸收体的中红外Er^(3+):ZBLAN锁模激光器及其波长可调谐性能

石墨烯与过渡金属硫化物WS_(2)具有稳定的化学性质和宽带吸收光谱,可以实现中红外波段激光的脉冲运转。本文报道了石墨烯/WS_(2)作为可饱和吸收体在中红外波段锁模激光器中的应用,实验证明石墨烯/WS_(2)复合材料具有更好的非线性吸收特性,锁模调制时表现出低的锁模阈值和高的材料损伤阈值。当泵浦功率为5 W时,激光器在2781.7 nm处得到了脉冲宽度为24.04 ps的锁模脉冲,激光器的最大平均输出功率为237.7 mW,峰值功率为395.5 W。最后,通过光栅实现了激光器的波长可调谐输出,将石墨烯/WS_(2)锁模激光器的输出波长范围拓宽为2730~2810 nm。

MnFe_(2)O_(4)/graphene的制备及其超级电容性能

采用水热法制备了MnFe_(2)O_(4)/石墨烯(MFO/graphene)复合材料。利用XRD、SEM、EDS、循环伏安、计时电位等手段对MFO/graphene的物理与化学性能进行了表征。结果表明:产物为直径约100 nm的MFO颗粒均匀分布于graphene的片层上;MFO/graphene复合材料在3M KOH溶液中表现较好的超级电容特性。由于graphene的引入,提高了MFO材料导电性,进而改善了复合材料的电化学性能,MFO/graphene电极材料在1 A·g^(-1)的电流密度下展现出600 F·g^(-1)的比容量,与MFO相比,比电容提高了近47.1%。

Reduced graphene oxide aerogel decorated with Mo_(2)C nanoparticles toward multifunctional properties of hydrophobicity,thermal insulation and microwave absorption

Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior microstructure,as well as good compatibility with other electromagnetic(EM)components.Herein,we realized the decoration of rGO aerogel with Mo_(2)C nanoparticles by sequential hydrothermal assembly,freeze-drying,and high-temperature pyrolysis.Results show that Mo_(2)C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio.The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo_(2)C nanoparticles,and more importantly,these nanoparticles regulate the EM properties of the rGO aerogel to a large extent.Although more Mo_(2)C nanoparticles may decrease the overall attenuation ability of the rGO aerogel,they bring much better impedance matching.At a molar ratio of 1:1,a desirable balance between attenuation ability and impedance matching is observed.In this context,the Mo_(2)C/r GO aerogel displays strong reflection loss and broad response bandwidth,even with a small applied thickness(1.7 mm)and low filler loading(9.0wt%).The positive effects of Mo_(2)C nanoparticles on multifunctional properties may render Mo_(2)C/r GO aerogels promising candidates for high-performance EWAMs under harsh conditions.

Mixed‑Dimensional Assembly Strategy to Construct Reduced Graphene Oxide/Carbon Foams Heterostructures for Microwave Absorption,Anti‑Corrosion and Thermal Insulation

Considering the serious electromagnetic wave(EMW)pollution problems and complex application condition,there is a pressing need to amalgamate multiple functionalities within a single substance.However,the effective integration of diverse functions into designed EMW absorption materials still faces the huge challenges.Herein,reduced graphene oxide/carbon foams(RGO/CFs)with two-dimensional/three-dimensional(2D/3D)van der Waals(vdWs)heterostructures were meticulously engineered and synthesized utilizing an efficient methodology involving freeze-drying,immersing absorption,secondary freeze-drying,followed by carbonization treatment.Thanks to their excellent linkage effect of amplified dielectric loss and optimized impedance matching,the designed 2D/3D RGO/CFs vdWs heterostructures demonstrated commendable EMW absorption performances,achieving a broad absorption bandwidth of 6.2 GHz and a reflection loss of-50.58 dB with the low matching thicknesses.Furthermore,the obtained 2D/3D RGO/CFs vdWs heterostructures also displayed the significant radar stealth properties,good corrosion resistance performances as well as outstanding thermal insulation capabilities,displaying the great potential in complex and variable environments.Accordingly,this work not only demonstrated a straightforward method for fabricating 2D/3D vdWs heterostructures,but also outlined a powerful mixeddimensional assembly strategy for engineering multifunctional foams for electromagnetic protection,aerospace and other complex conditions.

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.

Graphene-based electrodes and catalysts for electroreduction of CO_(2)to low-carbon alcohols

The electrochemical reduction of CO_(2)(CO_(2)ER)into the renewable and sustainable green fuels,such as low-carbon alcohols,is one of several workable strategies.CO_(2)ER can be combined with renewable electricity to transform intermittent energy sources(such as wind,hydro,and solar)into a fuel that can be stored until it is ready to be used.The intrinsic characteristics of the employed catalyst have a significant and substantial effect on the efficiency of CO_(2)ER and the ensuing economic viability.The paradigmatic multicarbon alcohol catalysts should increase the concentration of*CO in the reaction environment,stabilize the key intermediate products during the reaction,and facilitate the C-C coupling interaction.Since graphene has a large surface area and exceptional conductivity,it has been used as a support for active phases(nanoparticles or nanosheets).It is possible for graphene to enhance charge transport and accelerate CO_(2)conversion through its electronic and structural coupling effects.At the interface,a synergy can be produced that improves CO_(2)ER by increasing*CO adsorption,intermediate binding,and stability.This article focuses on recent advancements in graphene-based catalysts that promote CO_(2)ER to alcohols.Likewise,this paper also describes and discusses the key role graphene plays in catalyzing CO_(2)ER into alcohols.Finally,we hope to provide future ideas for the design of graphene-based electrocatalysts.

Supplementary Materials: Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

1. The transient absorption spectra of the WS2 monolayer sample.In the measurement of the transient absorption spectra of the WS2 monolayer sample, A 400-nm (3.1eV) pump pulse with a peak fluence of about 10μJ/cm2excites the electrons from the valence band into the conduction band,the

Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

Using dual graphene–WS2 quadrilayer heterostructures as an example, we find that the ultrafast transfer of electrons from WS2 to graphene takes place within 114 fs, and the Coulomb field of the charge can effectively affect the interlayer electron transfer. This effect illustrates that the charge transfer in such van der Waals heterostructures may be controlled by an externally applied electric field for promising applications in photoelectric devices.

Graphene/ZrO_2复合陶瓷材料的热导性能研究

采用3Y-ZrO_2粉体和石墨烯(Graphene)为原料,利用放电等离子体烧结技术(SPS),烧结制备了Graphene/ZrO_2复合陶瓷材料。利用SEM、HRTEM、XRD、激光热导仪等研究了烧结温度和石墨烯含量对Graphene/ZrO_2复合陶瓷材料的显微结构、物相和热传导性能的影响。研究结果表明,引入石墨烯不但可以抑制ZrO_2晶粒的生长,而且对复合材料的热传导性有着显著的影响;相对于单相ZrO_2陶瓷,随着石墨烯的引入,Graphene/ZrO_2复合陶瓷材料扩散系数反而降低,其原因可以归结于三个方面:首先,石墨烯含量比较低(0.5~1.5wt%),其次,石墨烯与Zr O晶粒界面处产生的强声子散射作用导致热导下降,最后是Graphene/ZrO_2复合陶瓷材料没有完全致密。

锂离子负极材料NiFe_2O_4/Graphene复合材料的制备和电化学性能

通过水热法合成了NiFe2O4/Graphene纳米复合材料,采用XRD和SEM对其晶相结构和形貌进行了表征,并将其作为锂离子电池活性材料组装成模拟电池,考查电化学性能。结果表明NiFe2O4/Graphene复合材料在100mA/g的电流密度下首次放电容量达970mAh/g,循环20次后,容量保持在668mAh/g,相比纯的NiFe2O4,具有较好的循环稳定性,这种优异的电化学性能归因于复合材料的纳米结构和NiFe2O4与Graphene的协同作用。

Sb_(2)S_(3)/石墨烯负极材料的制备及其储钠性能研究

钠离子电池(sodium-ion batteries,SIBs)具有成本低的潜在优势,有望成为替代锂离子电池(lithium ion batteries,LIBs)的储能设备。为提升钠离子电池的性能,开发出适应钠离子脱嵌的负极材料尤为重要。硫化锑(Sb_(2)S_(3))因其理论比容量高被认为是较好的钠离子电池负极材料。本文使用简单水热法将Sb_(2)S_(3)与石墨烯复合,制备Sb_(2)S_(3)/石墨烯复合材料(Sb_(2)S_(3)/Gr)。结果表明:Sb_(2)S_(3)/Gr作为钠离子电池负极时,不仅表现出良好的电导率(3.5×10~(-3)S/cm)和钠离子扩散速率(4.853×10~(-13)cm~2/s),而且在0.5 A/g的电流密度下,首圈库伦效率为76.27%,经150次循环后的比容量稳定在488 m A·h/g,表现出较高的比容量。Sb_(2)S_(3)/Gr复合材料表现出了极大的应用潜力,为高性能钠离子电池负极材料的研发提供了一定的参考价值。

GQDs/WS_(2)/Fe_(3)O_(4)磁分离适配体荧光传感器构建及其在甲胎蛋白中的应用

以聚乙二醇化石墨烯量子点标记的适配体(GQDs-PEG-Apt)作为甲胎蛋白(AFP)的特异性识别分子和能量供体,以WS_(2)/Fe_(3)O_(4)纳米复合物为单一能量受体,构建磁分离适配体荧光传感器并用血清AFP定量检测。样本中没有AFP时,能量供体与受体间π-π堆积作用和非辐射共振能力转移(FRET)令GQDs-PEG-Apt荧光猝灭;存在AFP时,GQDs-PEG-Apt与靶标结合并从WS_(2)/Fe_(3)O_(4)纳米复合物表面脱离,体系荧光强度得以恢复;经过磁性分离后,传感体系上清液487 nm处荧光强度随AFP浓度增大而增强;浓度在5~1000 ng/mL范围内,传感体系荧光相对恢复值与AFP浓度呈现良好的线性关系,线性相关系数为0.989。构建的传感器具有良好的特异性,可实现血清AFP定量检测,其检测限(LOD)为0.5 pg/mL,相对标准偏差(RSD)为3.32%~6.41%,回收率为91.92%~99.28%。

Graphene Quantum Dot‑Mediated Atom‑Layer Semiconductor Electrocatalyst for Hydrogen Evolution

The hydrogen evolution reaction performance of semiconducting 2H-phase molybdenum disulfide(2H-MoS_(2))presents a significant hurdle in realizing its full potential applications.Here,we utilize theoretical calculations to predict possible functionalized graphene quantum dots(GQDs),which can enhance HER activity of bulk MoS_(2).Subsequently,we design a functionalized GQD-induced in-situ bottom-up strategy to fabricate near atom-layer 2H-MoS_(2) nanosheets mediated with GQDs(ALQD)by modulating the concentration of electron withdrawing/donating functional groups.Experimental results reveal that the introduction of a series of functionalized GQDs during the synthesis of ALQD plays a crucial role.Notably,the higher the concentration and strength of electron-withdrawing functional groups on GQDs,the thinner and more active the resulting ALQD are.Remarkably,the synthesized near atom-layer ALQD-SO_(3)demonstrate significantly improved HER performance.Our GQD-induced strategy provides a simple and efficient approach for expanding the catalytic application of MoS_(2).Furthermore,it holds substantial potential for developing nanosheets in other transition-metal dichalcogenide materials.

Porous heterostructure of graphene/hexagonal boron nitride as an efficient electrocatalyst for hydrogen peroxide generation

Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous carbon materials composed of abundant graphene/hexagonal boron nitride(G/h-BN)heterostructures.Metal Ni powder and nanoscale h-BN sheets are used as a catalytic substrate/hard template and“nucleation seed”for the formation of the heterostructure,respectively.As-prepared G/h-BN heterostructures exhibit enhanced electrocatalytic activity toward H_(2)O_(2) generation with 86%-95%selectivity at the range of 0.45-0.75 V versus reversible hydrogen electrode(RHE)and a positive onset potential of 0.79 versus RHE(defined at a ring current density of 0.3 mA cm^(-2))in the alkaline solution.In a flow cell,G/h-BN heterostructured electrocatalyst has a H_(2)O_(2) production rate of up to 762 mmol g_(catalyst)^(-1) h^(-1) and Faradaic efficiency of over 75%during 12 h testing,superior to the reported carbon-based electrocatalysts.The density functional theory simulation suggests that the B atoms at the interface of the G/h-BN heterostructure are the key active sites.This research provides a new route to activate carbon catalysts toward highly active and selective O_(2)-to-H_(2)O_(2) conversion.

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。