Graphene oxide paper （GOP） can be prepared through simplified filtration of a graphite oxide solution. It possesses similar properties to graphene. In this study, the graphite oxide solution was synthesized from com...Graphene oxide paper （GOP） can be prepared through simplified filtration of a graphite oxide solution. It possesses similar properties to graphene. In this study, the graphite oxide solution was synthesized from commercial graphite by means of Hummer＇s method. It corresponds to the dried GOP that was prepared by deposition on a cellulose filter. It is found that the mesophase of the dried graphene oxide papers obtained from the graphite was thermotropic hexagonal columnar liquid crystal. Its higher temperature transitions were found at 80 ℃, 150 ℃ and 170 ℃-180 ℃. Therefore, it could be used for thermal storage and conductive materials in the future.展开更多
The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries(LIBs).However,traditional recycling methods still have limitations because of such h...The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries(LIBs).However,traditional recycling methods still have limitations because of such huge amounts of spent LIBs.Therefore,we proposed an ecofriendly and sustainable double recycling strategy to concurrently reuse the cathode(LiCoO_(2))and anode(graphite)materials of spent LIBs and recycled LiCoPO_(4)/graphite(RLCPG)in Li^(+)/PF^(-)_(6) co-de/intercalation dual-ion batteries.The recycle-derived dualion batteries of Li/RLCPG show impressive electrochemical performance,with an appropriate discharge capacity of 86.2 mAh·g^(-1) at25 mA·g^(-1) and 69%capacity retention after 400 cycles.Dual recycling of the cathode and anode from spent LIBs avoids wastage of resources and yields cathode materials with excellent performance,thereby offering an ecofriendly and sustainable way to design novel secondary batteries.展开更多
Over the span of years, improvements over various synthesis methods of graphene are constantly pursued to provide safer and more effective alternatives. Though the extraction of graphene through Hummers method is one ...Over the span of years, improvements over various synthesis methods of graphene are constantly pursued to provide safer and more effective alternatives. Though the extraction of graphene through Hummers method is one of the oldest techniques yet it is one of the most suitable methods for the formation of bulk graphene. Graphene can be obtained in the form of reduced Graphite oxide, sometimes also referred as Graphene oxide. The effectiveness of this oxidation process can be evaluated by the magnitude of carbon/oxygen ratio of the obtained graphene. Here, graphene oxide (GO) was prepared by oxidizing the purified natural flake graphite (NFG) by a modified Hummers method. The attempts have been made to synthesize GO having few layers by using a modified Hummers method where the amount of NaNO3 has been decreased, and the amount of KMnO4 is increased. The reaction has been performed in a 9:1 (by volume) mixture of H2SO4/H3PO4. This modification is successful in increasing the reaction yield and reducing the toxic gas evolution while using a varied proportion of KMnO4 and H2SO4 as those required by Hummers method. A new component of K2S2O8 has been introduced to the reaction system to maintain the pH value. Reduced graphene oxide (rGO) was thereafter extracted by thermal modification of GO. Here, GO has been used as a precursor for graphene synthesis by thermal reduction processes. The results of FTIR and Raman spectroscopy analysis show that the NFG when oxidized by strong oxidants like KMnO4 and NaNO3, introduced oxygen atoms into the graphite layers and formed bonds like C=O, C-H, COOH and C-O-C with the carbon atoms in the graphite layers. The structure and morphology of both GO and rGO were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).展开更多
Graphene oxide (GO) was chemically synthesized from natural flake graphite (NFG) using the simplified Hummers method. The synthesis was carried out using two routes. The first route involved stirring the one pot mixtu...Graphene oxide (GO) was chemically synthesized from natural flake graphite (NFG) using the simplified Hummers method. The synthesis was carried out using two routes. The first route involved stirring the one pot mixture continuously for three days at ambient temperature while the second route involved stirring another one pot mixture for six days also at ambient temperature. The two GOs were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-Ray Spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FE-SEM), Raman Spectroscopy and UV-Visible Spectrometry. The FTIR spectra showed introduction of oxygen functionalities in both GO with a higher degree of oxidation in the 6-day synthesized GO while the EDX confirmed the presence of carbon and oxygen in the GOs. The SEM micrograph gave the typical wrinkle and crumpling present in the 3-day synthesized GO while the 6-day synthesized GO showed distortion in structures. The Raman spectra showed a slightly higher ID/IG ratio for the 3-day synthesized GO with the 6-day synthesized GO showing a greater disruption of the sp2 domains. The extended period of stirring and oxidation increased the band gap of the 6-day synthesized GO to 3.0 eV unlike the 3-day synthesized GO where 2.5 eV was observed.展开更多
The graphite oxide(GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene dope...The graphite oxide(GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene doped ZnO, an alternative transparent conducting oxide(TCO) for solar cell applications. The samples were characterized by Raman spectrometer, X-ray diffractometer, Fourier transform infrared spectroscopy and scanning electron microscope, and compared with widely used aluminum doped ZnO(AZO) in resistivity and transmissivity. The results show that the transmissivity of graphene doped ZnO reaches the same level as that of AZO in visible light band. In ultraviolet light wave band, the transmissivity of graphene doped ZnO reaches as high as 50%, exceeding that of AZO which is only 20%. The resistivity of optimized graphene doped ZnO is1.03 × 10-5Ω· m, approaching AZO resistivity which is about 10-4—10-6Ω· m. As a result, graphene doped ZnO may have potential applications in the area of TCO due to its low cost and high performance.展开更多
SnO2/ graphite nanocomposites with different SnO2 contents were successfully prepared by a co-precipitation method.The nanocomposites, used as the anode material for lithium-ion batteries( LIBs),were characterized by ...SnO2/ graphite nanocomposites with different SnO2 contents were successfully prepared by a co-precipitation method.The nanocomposites, used as the anode material for lithium-ion batteries( LIBs),were characterized by X-ray diffraction( XRD),thermogravimetric analysis( TGA), and transmission electron microscopy( TEM). The SnO2 particles had the average size of about 15 nm and their distribution on graphite matrix much depended on the contents of SnO2 in the nanocomposites. The galvanostatic charge-discharge cycles were used to investigate the effects of SnO2 contents on the electrochemical performance of these composites. The results show that the initial specific capacities increase with the SnO2 contents. However,the cyclic stabilities are determined by the distribution of SnO2 particles in composites. For55% by weight SnO2/ graphite composites, the initial specific capacity is 740 m Ah g- 1and 70% of the initial specific capacity( 518 m Ah·g- 1) can still be retained after 50 charge-discharge cycles.展开更多
Graphene oxide was synthesized from graphite flakes using modified Hummers’method.The interlayer spacings of graphite,graphite oxide and graphene oxide were measured using X-ray diffraction technique.The C/O atomic r...Graphene oxide was synthesized from graphite flakes using modified Hummers’method.The interlayer spacings of graphite,graphite oxide and graphene oxide were measured using X-ray diffraction technique.The C/O atomic ratios of graphite oxide and graphene oxide were calculated from XPS measurements.The transformation of graphite to graphite oxide and finally to graphene oxide was clearly observed from the micro-Raman spectroscopy data and was confirmed from the FESEM micrographs.UV-VIS-NIR spectrophotometer was used to study the absorbance of graphene oxide and reduced graphene oxide samples.Finally,the chemically reduced graphene oxide was heat-treated in air to obtain chemically modified graphene.展开更多
Graphene Oxide (GO) was chemically synthesized from Natural Flake Graphite (NFG). The GO was chemically reduced to Reduced Graphene Oxide (RGO) using hydrazine monohydrate. Thin films of GO and RGO were also deposited...Graphene Oxide (GO) was chemically synthesized from Natural Flake Graphite (NFG). The GO was chemically reduced to Reduced Graphene Oxide (RGO) using hydrazine monohydrate. Thin films of GO and RGO were also deposited on sodalime glass substrate using spray pyrolysis technique (SPT). The samples were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDS) facility attached to it, UV-Visible Spectrometry and Four-Point probe. The FTIR spectra showed the addition of oxygen functionality groups in GO while such groups was drastically reduced in RGO. SEM micrograph of GO thin film showed a porous sponge-like structure while the micrograph of RGO thin film showed evenly distributed and well connected graphene structure. The EDX spectrum of RGO showed that there was decrease in oxygen content and increase in carbon content of RGO when compared to GO. The optical analysis of the GO and RGO thin films gave a direct energy bandgap of 2.7 eV and 2.2 eV respectively. The value of sheet resistance of GO and RGO films was determined to be 22.9 × 10<sup>6</sup>Ω/sq and 4.95 × 10<sup>6</sup>Ω/sq respectively.展开更多
The recycling of anode graphite plays a crucial role in the overall recycling process of spent lithium-ion batteries(LIBs).In this study an environmentally friendly and cost-effective recycling method was proposed.The...The recycling of anode graphite plays a crucial role in the overall recycling process of spent lithium-ion batteries(LIBs).In this study an environmentally friendly and cost-effective recycling method was proposed.The spent graphite(SG)from LIBs was used to prepare graphene nanoplates(GNP)materials through a mechanochemical process without any additives.To figure out the mechanochemical mechanism within,we set the control group with pure graphite(PG).Characterization of SG and PG produced materials using XRD,Raman,XPS,IR,and BET analyses revealed the presence of oxygen-containing functional groups on the surface of SG-based GNP materials,along with a high specific surface area of 275.4 m^(2)/g and pore volume of 0.568 cm^(3)/g.Through an in-depth investigation of the electrochemical capacity of the GNP materials fabricated by SG,the specific capacitance per unit area of the graphite material is 10.10μF/cm^(2),revealing the intricate pore structure of GNP materials primarily contributes to the electrochemical capacity.展开更多
With extensive use of lithium ion batteries （LIBs）, amounts of LIBs were discarded, giving rise to growth of resources demand and environmental risk. In view of wide usage of natural graphite and the high content （...With extensive use of lithium ion batteries （LIBs）, amounts of LIBs were discarded, giving rise to growth of resources demand and environmental risk. In view of wide usage of natural graphite and the high content （12%-21%） of anode graphite in spent LIBs, recycling anode graphite from spent LIBs cannot only alleviate the shortage of natural graphite, but also promote the sustainable development of related industries. After calcined at 600°Cfor 1 h to remove organic substances, anode graphite was used to prepare graphene by oxidation-reduction method. Effect of pH and N2H4·H2O amount on reduction of graphite oxide were probed. Structure of graphite, graphite oxide and graphene were characterized by XRD, Raman and FTIR. Graphite oxide could be completely reduced to graphene at pH 11 and 0.25 mL N2H4·H2O. Due to the presence of some oxygen-containing groups and structure defects in anode graphite, concentrated H2SO4 and KMnO4 consumptions were 40% and around 28.6% less than graphene preparation from natural graphite, respectively.展开更多
Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties.With excellent ...Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties.With excellent electrical conductivity of 6000 S/cm, which is independent on chirality, graphene is a promising material for high-performance nanoelectronics, transparent conductor, as well as polymer composites. On account of its Young's Modulus of 1 TPa and ultimate strength of 130 GPa, isolated graphene sheet is considered to be among the strongest materials ever measured. Comparable with the single-walled carbon nanotube bundle,graphene has a thermal conductivity of 5000 W/(m·K), which suggests a potential application of graphene in polymer matrix for improving thermal properties of the graphene/polymer composite. Furthermore, graphene exhibits a very high surface area, up to a value of 2630 m^2/g. All of these outstanding properties suggest a wide application for this nanometer-thick, two-dimensional carbon material. This review article presents an overview of the significant advancement in graphene research: preparation, functionalization as well as the properties of graphene will be discussed. In addition, the feasibility and potential applications of graphene in areas, such as sensors, nanoelectronics and nanocomposites materials, will also be reviewed.展开更多
A one-pot method for the preparation of g-C3N4/reduced graphene oxide(rGO)composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spec...A one-pot method for the preparation of g-C3N4/reduced graphene oxide(rGO)composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spectroscopy,X-ray diffraction,scanning electron microscope,transmission electron microscope,and Mott-Schottky analysis.The valance band(VB)of g-C3N4 exhibits a noticeable positive shift upon hybridizing with rGO,and thus results in a strong photo-oxidation ability.The g-C3N4/rGO composites show a higher photodegradation activity for 2,4-dichlorophenol(2,4-DCP)and rhodamine B(RhB)under visible light irradiation(λ≥420 ran).The g-C3N4/rGO-1sample exhibits the highest photocatalytic activity,which is 1.49 and 1.52 times higher than that of bulk g-C3N4 for 2,4-DCP and 1.52 times degradation,respectively.The enhanced photocatalytic activity for g-C3N4 originates from the improved visible light usage,enhanced electronic conductivity and photo-oxidation ability by the formed strongπ-πstacking interactions with rGO.展开更多
Synthesis of structurally controlled graphene materials is critical for realizing their practical applications.The electrochemical exfoliation of graphite has emerged as a simple method to produce graphene materials.T...Synthesis of structurally controlled graphene materials is critical for realizing their practical applications.The electrochemical exfoliation of graphite has emerged as a simple method to produce graphene materials.This review examines research progress in the last 5 years,from 2015 to 2019.Graphene material synthesis methods generally have a trade‐off between increasing production yield and achieving better material property control.The synthesis conditions for synthesizing pristine graphene,graphene oxide(GO),and graphene composites are significantly different.Thus,in this review,we first discuss synthesis methods for graphene materials with high C/O ratios from four aspects:graphite electrodes,equipment engineering,electrolytes,and additional reduction methods.Next,we survey synthesis methods for GO and examine how the pretreatment of the graphite electrodes,electrolytes,and operation parameters,such as applied voltages,electrolyte temperatures,and mechanical forces,affect the quality of GO.Further,we summarize electrochemical exfoliation methods used to dope graphene materials,introduce covalent functional groups,incorporate various nanoparticles,and assembly of graphene architectures.For all synthesis methods,we compare the properties of resulting graphene materials such as C/O ratios,lateral size,layer numbers,and quality characterized by Raman spectroscopy.Lastly,we propose our perspectives on further research.We hope this review stimulates more studies to realize the on‐demand production of graphene materials with desired properties using electrochemical exfoliation methods.展开更多
Coaly graphite is an important natural graphite resource that derived from coal under a natural process that associated with igneous intrusion.Flake graphite is usually used for the chemical synthesis of graphene oxid...Coaly graphite is an important natural graphite resource that derived from coal under a natural process that associated with igneous intrusion.Flake graphite is usually used for the chemical synthesis of graphene oxide(GO),the main precursor for preparation of graphene,but few papers pay attention to preparing GO using coaly graphite.In this paper,four kinds of natural coaly graphite with different graphitization degrees were exposed to a modified Hummer’s oxidation method to prepare GO.The flake graphite sample was also used for comparison.The results showed that the structural change process from graphite to GO were significantly affected by the graphitization degree of the original coaly graphite.The relationship between yields of GO and graphitization degrees of the coaly graphite was explored.The mechanism of why the graphite with low graphitization degrees cannot be totally oxidized was proposed.Coaly graphite with a graphitization degree of higher than 80% was easier to be oxidized and yielded the same amount of GO as the flake graphite did,suggesting it is the potential substitute for the flake graphite to produce GO in bulk quantities.展开更多
Heteroatom doped graphitic porous carbon is highly desirable for electrochemical applications because of its excellent conductivity and high surface area.In this study,highly uniform Co-Ni oxide nanoparticleloaded B,N...Heteroatom doped graphitic porous carbon is highly desirable for electrochemical applications because of its excellent conductivity and high surface area.In this study,highly uniform Co-Ni oxide nanoparticleloaded B,N-doped hierarchical graphitic porous carbon was prepared through a dual pyrolysis process.Graphene dispersed chitosan hydrogel was first used as a precursor to fabricate the porous carbon(GCS–C)at 700℃.Co and Ni oxide nanoparticles were further anchored on the porous carbon through chemical reduction and calcined at high temperature.The structure of the porous carbon was optimized by the introduction of graphene to the chitosan hydrogel.The graphitic degree of the porous carbon was significantly improved by the Co and Ni species.The heteroatom B and N were found to be well doped in the composite.These features enable the composite to be an excellent candidate for supercapacitor electrodes.The composite demonstrates a high capacitance(1266.7 F g-1 at 1 A g-1)and excellent stability.展开更多
Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process wit...Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process with graphite and graphene oxide,as heterogeneous templates,were investigated.More than 640 hanging drops with different concentrations of Lysozyme(30,50,70,100 mg/mL)and NaCl(0.7,0.9,1.1,1.3,1.5 M)were crystallised at 4 ℃ with or without graphite/graphene oxide templates.The induction times and crystallization process were observed under the microscope.The lysozyme in the solutions with graphite flakes nucleated faster under all the conditions than the lysozyme with equal experimental conditions without templates.The crystals preferred to grow around the edge of graphite flakes than on the flat surfaces.In the droplets with monolayer graphene oxide,more crystals appeared around gra-phene oxide particles,and the faster or slower nucleation processes with templates were dependent on the lysozyme and NaCl concentrations.Graphene oxide templates strongly inhibited nucleation at high lysozyme concentrations but promoted nucleation at low lysozyme concentrations.Both heterogeneous templates changed the crystal morphology and the crystallization kinetics.More crystals were observed in the solution with graphite templatesthan with graphene oxide templates and without any template.展开更多
Advanced membrane systems with excellent permeance are important for controllable separation processes,such as gas separation and water purification.The ideal candidate materials should be very thin to provide high pe...Advanced membrane systems with excellent permeance are important for controllable separation processes,such as gas separation and water purification.The ideal candidate materials should be very thin to provide high permeance,be stiff enough to withstand working under high applied pressure,with a large surface area and micro-or nano-pore structure for excellent selectivity.Graphene oxide(GO)nanosheets are graphene with oxygen-containing functional groups,obtained by treating graphite with strong oxidizers.Graphene-based materials,by virtue of their high mechanical strength,large surface area,singleatom-thick unique two-dimensional honeycomb lattice structure,and narrow pore distribution,provide exciting opportunities to assemble novel types of advanced,ultra-thin,high-efficiency membrane devices.In this contribution,we discuss the progress made in the direction of using graphene oxide as high-efficiency membranes for gas separation and water purification.The primary focus will be on introducing the fabrication processes,exceptional properties,and innovative membrane applications of twodimensional graphene oxide materials for controllable separation processes.This state-of-the-art review will provide a platform for understanding the intricate details of gas and water molecular transport through laminar graphene oxide membranes,as well as a summary of the latest process in the field.展开更多
The advancement of the extraction of uranium(Ⅵ)(U(Ⅵ))from seawater holds significant strategic importance for the sustainable progression of nuclear energy.In this study,the photocatalyst heterojunction of graphene ...The advancement of the extraction of uranium(Ⅵ)(U(Ⅵ))from seawater holds significant strategic importance for the sustainable progression of nuclear energy.In this study,the photocatalyst heterojunction of graphene oxide/graphitic carbon nitride(GO/g-C_(3)N_(4))was encapsulated by the spinning of fiber to obtain a graphene oxide/graphitic carbon nitride/polyamide oxime(GO/g-C_(3)N_(4)/PAO)film with adsorption and photoreduction ability toward U(Ⅵ).The enhanced adsorption capacity of the GO/g-C_(3)N_(4)/PAO nanofiber was achieved through the synergistic effects of the aminoxime group in PAO and the photocatalytic performance of GO/g-C_(3)N_(4).The GO/g-C_(3)N_(4)/PAO composite exhibited an adsorption capacity of 190.7 mg g−1(pH=6,t=600 min,C0=99.9 mg L^(−1),and m/v=0.5 g L^(−1))under light conditions.GO/g-C_(3)N_(4)/PAO showed good recycling reproducibility following five cycles of adsorption.After 30 days of adsorption in natural seawater,the adsorption capacity of GO/g-C_(3)N_(4)/PAO for U(Ⅵ)was 10.39 mg g−1,representing a 38.6%increase compared to its performance in the absence of light.The favorable adsorption characteristics exhibited by the GO/g-C_(3)N_(4)/PAO composite suggest its potential as a viable option for the extraction of uranium from seawater.展开更多
文摘Graphene oxide paper （GOP） can be prepared through simplified filtration of a graphite oxide solution. It possesses similar properties to graphene. In this study, the graphite oxide solution was synthesized from commercial graphite by means of Hummer＇s method. It corresponds to the dried GOP that was prepared by deposition on a cellulose filter. It is found that the mesophase of the dried graphene oxide papers obtained from the graphite was thermotropic hexagonal columnar liquid crystal. Its higher temperature transitions were found at 80 ℃, 150 ℃ and 170 ℃-180 ℃. Therefore, it could be used for thermal storage and conductive materials in the future.
基金the National Natural Science Foundation of China(No.52173246)the Science and Technology Planning Project of Guangzhou City,China(No.2023B03J1278)。
文摘The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries(LIBs).However,traditional recycling methods still have limitations because of such huge amounts of spent LIBs.Therefore,we proposed an ecofriendly and sustainable double recycling strategy to concurrently reuse the cathode(LiCoO_(2))and anode(graphite)materials of spent LIBs and recycled LiCoPO_(4)/graphite(RLCPG)in Li^(+)/PF^(-)_(6) co-de/intercalation dual-ion batteries.The recycle-derived dualion batteries of Li/RLCPG show impressive electrochemical performance,with an appropriate discharge capacity of 86.2 mAh·g^(-1) at25 mA·g^(-1) and 69%capacity retention after 400 cycles.Dual recycling of the cathode and anode from spent LIBs avoids wastage of resources and yields cathode materials with excellent performance,thereby offering an ecofriendly and sustainable way to design novel secondary batteries.
文摘Over the span of years, improvements over various synthesis methods of graphene are constantly pursued to provide safer and more effective alternatives. Though the extraction of graphene through Hummers method is one of the oldest techniques yet it is one of the most suitable methods for the formation of bulk graphene. Graphene can be obtained in the form of reduced Graphite oxide, sometimes also referred as Graphene oxide. The effectiveness of this oxidation process can be evaluated by the magnitude of carbon/oxygen ratio of the obtained graphene. Here, graphene oxide (GO) was prepared by oxidizing the purified natural flake graphite (NFG) by a modified Hummers method. The attempts have been made to synthesize GO having few layers by using a modified Hummers method where the amount of NaNO3 has been decreased, and the amount of KMnO4 is increased. The reaction has been performed in a 9:1 (by volume) mixture of H2SO4/H3PO4. This modification is successful in increasing the reaction yield and reducing the toxic gas evolution while using a varied proportion of KMnO4 and H2SO4 as those required by Hummers method. A new component of K2S2O8 has been introduced to the reaction system to maintain the pH value. Reduced graphene oxide (rGO) was thereafter extracted by thermal modification of GO. Here, GO has been used as a precursor for graphene synthesis by thermal reduction processes. The results of FTIR and Raman spectroscopy analysis show that the NFG when oxidized by strong oxidants like KMnO4 and NaNO3, introduced oxygen atoms into the graphite layers and formed bonds like C=O, C-H, COOH and C-O-C with the carbon atoms in the graphite layers. The structure and morphology of both GO and rGO were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).
文摘Graphene oxide (GO) was chemically synthesized from natural flake graphite (NFG) using the simplified Hummers method. The synthesis was carried out using two routes. The first route involved stirring the one pot mixture continuously for three days at ambient temperature while the second route involved stirring another one pot mixture for six days also at ambient temperature. The two GOs were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-Ray Spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FE-SEM), Raman Spectroscopy and UV-Visible Spectrometry. The FTIR spectra showed introduction of oxygen functionalities in both GO with a higher degree of oxidation in the 6-day synthesized GO while the EDX confirmed the presence of carbon and oxygen in the GOs. The SEM micrograph gave the typical wrinkle and crumpling present in the 3-day synthesized GO while the 6-day synthesized GO showed distortion in structures. The Raman spectra showed a slightly higher ID/IG ratio for the 3-day synthesized GO with the 6-day synthesized GO showing a greater disruption of the sp2 domains. The extended period of stirring and oxidation increased the band gap of the 6-day synthesized GO to 3.0 eV unlike the 3-day synthesized GO where 2.5 eV was observed.
基金the Natural Science Foundation of Shanghai(No.13ZR1428200)the National Project of University of Shanghai for Science and Technology(No.14XPM06)
文摘The graphite oxide(GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene doped ZnO, an alternative transparent conducting oxide(TCO) for solar cell applications. The samples were characterized by Raman spectrometer, X-ray diffractometer, Fourier transform infrared spectroscopy and scanning electron microscope, and compared with widely used aluminum doped ZnO(AZO) in resistivity and transmissivity. The results show that the transmissivity of graphene doped ZnO reaches the same level as that of AZO in visible light band. In ultraviolet light wave band, the transmissivity of graphene doped ZnO reaches as high as 50%, exceeding that of AZO which is only 20%. The resistivity of optimized graphene doped ZnO is1.03 × 10-5Ω· m, approaching AZO resistivity which is about 10-4—10-6Ω· m. As a result, graphene doped ZnO may have potential applications in the area of TCO due to its low cost and high performance.
基金the Scientific Research Foundation for the Returned Overseas Chinese Scholarsthe Shanghai Leading Academic Discipline Project,China(No.B603)the Programme of Introducing Talents of Discipline to Universities,China(No.111-2-04)
文摘SnO2/ graphite nanocomposites with different SnO2 contents were successfully prepared by a co-precipitation method.The nanocomposites, used as the anode material for lithium-ion batteries( LIBs),were characterized by X-ray diffraction( XRD),thermogravimetric analysis( TGA), and transmission electron microscopy( TEM). The SnO2 particles had the average size of about 15 nm and their distribution on graphite matrix much depended on the contents of SnO2 in the nanocomposites. The galvanostatic charge-discharge cycles were used to investigate the effects of SnO2 contents on the electrochemical performance of these composites. The results show that the initial specific capacities increase with the SnO2 contents. However,the cyclic stabilities are determined by the distribution of SnO2 particles in composites. For55% by weight SnO2/ graphite composites, the initial specific capacity is 740 m Ah g- 1and 70% of the initial specific capacity( 518 m Ah·g- 1) can still be retained after 50 charge-discharge cycles.
文摘Graphene oxide was synthesized from graphite flakes using modified Hummers’method.The interlayer spacings of graphite,graphite oxide and graphene oxide were measured using X-ray diffraction technique.The C/O atomic ratios of graphite oxide and graphene oxide were calculated from XPS measurements.The transformation of graphite to graphite oxide and finally to graphene oxide was clearly observed from the micro-Raman spectroscopy data and was confirmed from the FESEM micrographs.UV-VIS-NIR spectrophotometer was used to study the absorbance of graphene oxide and reduced graphene oxide samples.Finally,the chemically reduced graphene oxide was heat-treated in air to obtain chemically modified graphene.
文摘Graphene Oxide (GO) was chemically synthesized from Natural Flake Graphite (NFG). The GO was chemically reduced to Reduced Graphene Oxide (RGO) using hydrazine monohydrate. Thin films of GO and RGO were also deposited on sodalime glass substrate using spray pyrolysis technique (SPT). The samples were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDS) facility attached to it, UV-Visible Spectrometry and Four-Point probe. The FTIR spectra showed the addition of oxygen functionality groups in GO while such groups was drastically reduced in RGO. SEM micrograph of GO thin film showed a porous sponge-like structure while the micrograph of RGO thin film showed evenly distributed and well connected graphene structure. The EDX spectrum of RGO showed that there was decrease in oxygen content and increase in carbon content of RGO when compared to GO. The optical analysis of the GO and RGO thin films gave a direct energy bandgap of 2.7 eV and 2.2 eV respectively. The value of sheet resistance of GO and RGO films was determined to be 22.9 × 10<sup>6</sup>Ω/sq and 4.95 × 10<sup>6</sup>Ω/sq respectively.
基金supported by the National Natural Science Foundation of China(52470154)China Environmental Protection Foundation.
文摘The recycling of anode graphite plays a crucial role in the overall recycling process of spent lithium-ion batteries(LIBs).In this study an environmentally friendly and cost-effective recycling method was proposed.The spent graphite(SG)from LIBs was used to prepare graphene nanoplates(GNP)materials through a mechanochemical process without any additives.To figure out the mechanochemical mechanism within,we set the control group with pure graphite(PG).Characterization of SG and PG produced materials using XRD,Raman,XPS,IR,and BET analyses revealed the presence of oxygen-containing functional groups on the surface of SG-based GNP materials,along with a high specific surface area of 275.4 m^(2)/g and pore volume of 0.568 cm^(3)/g.Through an in-depth investigation of the electrochemical capacity of the GNP materials fabricated by SG,the specific capacitance per unit area of the graphite material is 10.10μF/cm^(2),revealing the intricate pore structure of GNP materials primarily contributes to the electrochemical capacity.
文摘With extensive use of lithium ion batteries （LIBs）, amounts of LIBs were discarded, giving rise to growth of resources demand and environmental risk. In view of wide usage of natural graphite and the high content （12%-21%） of anode graphite in spent LIBs, recycling anode graphite from spent LIBs cannot only alleviate the shortage of natural graphite, but also promote the sustainable development of related industries. After calcined at 600°Cfor 1 h to remove organic substances, anode graphite was used to prepare graphene by oxidation-reduction method. Effect of pH and N2H4·H2O amount on reduction of graphite oxide were probed. Structure of graphite, graphite oxide and graphene were characterized by XRD, Raman and FTIR. Graphite oxide could be completely reduced to graphene at pH 11 and 0.25 mL N2H4·H2O. Due to the presence of some oxygen-containing groups and structure defects in anode graphite, concentrated H2SO4 and KMnO4 consumptions were 40% and around 28.6% less than graphene preparation from natural graphite, respectively.
基金supported by the National Natural Science Foundation of China (No. 50902092 and 51102164)Science and Technology Commission of Shanghai Municipality (No. 1052nm06800 and 1052nm02000)+1 种基金Shanghai Pujiang Program (No. 11PJD011)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning
文摘Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties.With excellent electrical conductivity of 6000 S/cm, which is independent on chirality, graphene is a promising material for high-performance nanoelectronics, transparent conductor, as well as polymer composites. On account of its Young's Modulus of 1 TPa and ultimate strength of 130 GPa, isolated graphene sheet is considered to be among the strongest materials ever measured. Comparable with the single-walled carbon nanotube bundle,graphene has a thermal conductivity of 5000 W/(m·K), which suggests a potential application of graphene in polymer matrix for improving thermal properties of the graphene/polymer composite. Furthermore, graphene exhibits a very high surface area, up to a value of 2630 m^2/g. All of these outstanding properties suggest a wide application for this nanometer-thick, two-dimensional carbon material. This review article presents an overview of the significant advancement in graphene research: preparation, functionalization as well as the properties of graphene will be discussed. In addition, the feasibility and potential applications of graphene in areas, such as sensors, nanoelectronics and nanocomposites materials, will also be reviewed.
文摘A one-pot method for the preparation of g-C3N4/reduced graphene oxide(rGO)composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spectroscopy,X-ray diffraction,scanning electron microscope,transmission electron microscope,and Mott-Schottky analysis.The valance band(VB)of g-C3N4 exhibits a noticeable positive shift upon hybridizing with rGO,and thus results in a strong photo-oxidation ability.The g-C3N4/rGO composites show a higher photodegradation activity for 2,4-dichlorophenol(2,4-DCP)and rhodamine B(RhB)under visible light irradiation(λ≥420 ran).The g-C3N4/rGO-1sample exhibits the highest photocatalytic activity,which is 1.49 and 1.52 times higher than that of bulk g-C3N4 for 2,4-DCP and 1.52 times degradation,respectively.The enhanced photocatalytic activity for g-C3N4 originates from the improved visible light usage,enhanced electronic conductivity and photo-oxidation ability by the formed strongπ-πstacking interactions with rGO.
基金National Natural Science Foundation of China,Grant/Award Numbers:51678163,91851202Australian Research Council,Grant/Award Number:FT160100107 and DP180102210。
文摘Synthesis of structurally controlled graphene materials is critical for realizing their practical applications.The electrochemical exfoliation of graphite has emerged as a simple method to produce graphene materials.This review examines research progress in the last 5 years,from 2015 to 2019.Graphene material synthesis methods generally have a trade‐off between increasing production yield and achieving better material property control.The synthesis conditions for synthesizing pristine graphene,graphene oxide(GO),and graphene composites are significantly different.Thus,in this review,we first discuss synthesis methods for graphene materials with high C/O ratios from four aspects:graphite electrodes,equipment engineering,electrolytes,and additional reduction methods.Next,we survey synthesis methods for GO and examine how the pretreatment of the graphite electrodes,electrolytes,and operation parameters,such as applied voltages,electrolyte temperatures,and mechanical forces,affect the quality of GO.Further,we summarize electrochemical exfoliation methods used to dope graphene materials,introduce covalent functional groups,incorporate various nanoparticles,and assembly of graphene architectures.For all synthesis methods,we compare the properties of resulting graphene materials such as C/O ratios,lateral size,layer numbers,and quality characterized by Raman spectroscopy.Lastly,we propose our perspectives on further research.We hope this review stimulates more studies to realize the on‐demand production of graphene materials with desired properties using electrochemical exfoliation methods.
基金the financial support provided by the National Natural Science Foundation of China(41672150).
文摘Coaly graphite is an important natural graphite resource that derived from coal under a natural process that associated with igneous intrusion.Flake graphite is usually used for the chemical synthesis of graphene oxide(GO),the main precursor for preparation of graphene,but few papers pay attention to preparing GO using coaly graphite.In this paper,four kinds of natural coaly graphite with different graphitization degrees were exposed to a modified Hummer’s oxidation method to prepare GO.The flake graphite sample was also used for comparison.The results showed that the structural change process from graphite to GO were significantly affected by the graphitization degree of the original coaly graphite.The relationship between yields of GO and graphitization degrees of the coaly graphite was explored.The mechanism of why the graphite with low graphitization degrees cannot be totally oxidized was proposed.Coaly graphite with a graphitization degree of higher than 80% was easier to be oxidized and yielded the same amount of GO as the flake graphite did,suggesting it is the potential substitute for the flake graphite to produce GO in bulk quantities.
基金the financial support from the National Natural Science Foundation of China(Nos.51861005 and 51861004)the Innovation Project of GUET Graduate Education(2019YCXS113)+1 种基金the GUET Excellent Graduate Thesis Program(17YJPYSS32)the Guangxi Natural Science Foundation(2017AD23029).
文摘Heteroatom doped graphitic porous carbon is highly desirable for electrochemical applications because of its excellent conductivity and high surface area.In this study,highly uniform Co-Ni oxide nanoparticleloaded B,N-doped hierarchical graphitic porous carbon was prepared through a dual pyrolysis process.Graphene dispersed chitosan hydrogel was first used as a precursor to fabricate the porous carbon(GCS–C)at 700℃.Co and Ni oxide nanoparticles were further anchored on the porous carbon through chemical reduction and calcined at high temperature.The structure of the porous carbon was optimized by the introduction of graphene to the chitosan hydrogel.The graphitic degree of the porous carbon was significantly improved by the Co and Ni species.The heteroatom B and N were found to be well doped in the composite.These features enable the composite to be an excellent candidate for supercapacitor electrodes.The composite demonstrates a high capacitance(1266.7 F g-1 at 1 A g-1)and excellent stability.
基金grateful to the UK EPSRC(Engineering and Physical Sciences Research Council)for support(EP/T005378/1).
文摘Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies.Protein crystallization process with graphite and graphene oxide,as heterogeneous templates,were investigated.More than 640 hanging drops with different concentrations of Lysozyme(30,50,70,100 mg/mL)and NaCl(0.7,0.9,1.1,1.3,1.5 M)were crystallised at 4 ℃ with or without graphite/graphene oxide templates.The induction times and crystallization process were observed under the microscope.The lysozyme in the solutions with graphite flakes nucleated faster under all the conditions than the lysozyme with equal experimental conditions without templates.The crystals preferred to grow around the edge of graphite flakes than on the flat surfaces.In the droplets with monolayer graphene oxide,more crystals appeared around gra-phene oxide particles,and the faster or slower nucleation processes with templates were dependent on the lysozyme and NaCl concentrations.Graphene oxide templates strongly inhibited nucleation at high lysozyme concentrations but promoted nucleation at low lysozyme concentrations.Both heterogeneous templates changed the crystal morphology and the crystallization kinetics.More crystals were observed in the solution with graphite templatesthan with graphene oxide templates and without any template.
基金the Science Foundation of China University of Petroleum Beijing(no.2462014YJRC011)for support.
文摘Advanced membrane systems with excellent permeance are important for controllable separation processes,such as gas separation and water purification.The ideal candidate materials should be very thin to provide high permeance,be stiff enough to withstand working under high applied pressure,with a large surface area and micro-or nano-pore structure for excellent selectivity.Graphene oxide(GO)nanosheets are graphene with oxygen-containing functional groups,obtained by treating graphite with strong oxidizers.Graphene-based materials,by virtue of their high mechanical strength,large surface area,singleatom-thick unique two-dimensional honeycomb lattice structure,and narrow pore distribution,provide exciting opportunities to assemble novel types of advanced,ultra-thin,high-efficiency membrane devices.In this contribution,we discuss the progress made in the direction of using graphene oxide as high-efficiency membranes for gas separation and water purification.The primary focus will be on introducing the fabrication processes,exceptional properties,and innovative membrane applications of twodimensional graphene oxide materials for controllable separation processes.This state-of-the-art review will provide a platform for understanding the intricate details of gas and water molecular transport through laminar graphene oxide membranes,as well as a summary of the latest process in the field.
基金supported by the Natural Science Foundation of Qinghai Province(2024-ZJ-913).
文摘The advancement of the extraction of uranium(Ⅵ)(U(Ⅵ))from seawater holds significant strategic importance for the sustainable progression of nuclear energy.In this study,the photocatalyst heterojunction of graphene oxide/graphitic carbon nitride(GO/g-C_(3)N_(4))was encapsulated by the spinning of fiber to obtain a graphene oxide/graphitic carbon nitride/polyamide oxime(GO/g-C_(3)N_(4)/PAO)film with adsorption and photoreduction ability toward U(Ⅵ).The enhanced adsorption capacity of the GO/g-C_(3)N_(4)/PAO nanofiber was achieved through the synergistic effects of the aminoxime group in PAO and the photocatalytic performance of GO/g-C_(3)N_(4).The GO/g-C_(3)N_(4)/PAO composite exhibited an adsorption capacity of 190.7 mg g−1(pH=6,t=600 min,C0=99.9 mg L^(−1),and m/v=0.5 g L^(−1))under light conditions.GO/g-C_(3)N_(4)/PAO showed good recycling reproducibility following five cycles of adsorption.After 30 days of adsorption in natural seawater,the adsorption capacity of GO/g-C_(3)N_(4)/PAO for U(Ⅵ)was 10.39 mg g−1,representing a 38.6%increase compared to its performance in the absence of light.The favorable adsorption characteristics exhibited by the GO/g-C_(3)N_(4)/PAO composite suggest its potential as a viable option for the extraction of uranium from seawater.
