Due to its larger ionic radius,further studies are needed before graphite can be used as an anode for sodium/potassium-ion batteries(SIBs/KIBs).It is believed that doping and increasing the layer spacing can improve t...Due to its larger ionic radius,further studies are needed before graphite can be used as an anode for sodium/potassium-ion batteries(SIBs/KIBs).It is believed that doping and increasing the layer spacing can improve the Na+/K+storage.Herein,S/N co-doped graphite nanosheets(GNS)with an enlarged interlayer spacing of 0.39 nm were prepared via exfoliation with three-roll milling(TRM)combined with thiourea heated at different temperatures.This method generates abundant defects and active sites for GNS,as well as facilitates rapid access and transport of electrolytes and electrons/ions.The electrochemical results show that the S/N-doped GNS exfoliated 15 times and heated at 600°C(SNGNS15-600)with thiourea as the electrode delivers a discharge capacity of 94 mAh g–1 over 6000 cycles at 10 A g–1 with an enhanced rate capability and stable performance for application in SIBs.Calculations using density functional theory show that the increased interlayer spacing by TRM and S,N co-doping enhances the adsorption energies of Na+on graphite,thus improving the Na+storage.As the anode for KIBs,the SNGNS15-600 electrode has a capacity of 142 mAh g–1 after 5000 cycles at 0.5 A g–1.This study provides an essential theoretical basis for the effective exfoliation of layered graphite-based materials and their applications in energy storage.展开更多
For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC...For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.展开更多
Graphite nanosheets with the average thicknesses ranging from 24.4 to 48.9 nm were prepared with the use of expanded graphite as the raw material by sand milling in deionized water,anhydrous ethanol,glycerol,and 1,4-b...Graphite nanosheets with the average thicknesses ranging from 24.4 to 48.9 nm were prepared with the use of expanded graphite as the raw material by sand milling in deionized water,anhydrous ethanol,glycerol,and 1,4-butanediol,respectively.Anhydrous ethanol favored the formation of graphite nanosheets with a smaller average thickness.When the graphite nanosheets with the content of 2 wt%were added in lithium-based grease,the average friction coefficient decreased by 27%as compared with the pure lithium-based grease.The weld point and load wear index were 1.6 and 1.4 times those of the pure lithium-based grease,respectively.The tribological properties of the graphite nanosheet-containing lithium-based grease were comparable with those of the graphene-containing lithium-based grease.展开更多
Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation effici...Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.展开更多
By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic...By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.展开更多
The development of efficient electrocatalysts from Earth-abundant elements for the oxygen evolution reaction (OER) is highly desired.Here,we report the electrodeposition of a NiCo layered double hydroxide nanosheet ar...The development of efficient electrocatalysts from Earth-abundant elements for the oxygen evolution reaction (OER) is highly desired.Here,we report the electrodeposition of a NiCo layered double hydroxide nanosheet array on graphite felt (NiCo LDHs/GF) as a 3D OER electrocatalyst.Such NiCo LDHs/GF exhibits superior electrocatalytic activity with the need for an overpotential of 249 mV to drive a current density of 20 mA cm^(-2) in 1.0 M KOH.It also shows strong long-term electrochemical durability with its activity being maintained for at least 24 h.展开更多
Graphitic carbon nitride(g-C_(3)N_(4))nanosheets exfoliated from their bulk-sized counterparts are limited by a quantum size effect-induced widened bandgap.In this work,an(NH_(4))_(2)S_(2)O_(8)(APS)induced thermal exf...Graphitic carbon nitride(g-C_(3)N_(4))nanosheets exfoliated from their bulk-sized counterparts are limited by a quantum size effect-induced widened bandgap.In this work,an(NH_(4))_(2)S_(2)O_(8)(APS)induced thermal exfoliation approach is introduced to fabricate O-doped g-C_(3)N_(4)nanosheets(OCNs).During this calcination process,the thermal decomposition products(NH_(3)and H_(2)SO_(4))from APS not only efficiently promote delamination,but also introduce O doping into the g-C_(3)N_(4)structure,realizing the synchronization control of the electronic structure and morphology.展开更多
In this work,layered N-doped graphitic carbon nitride(g-C_(3)N_(4))porous nanosheets were successfully prepared by mixing the precursor of N,N-dimethylformamide(DMF)and urea through a simple one-step thermal copolymer...In this work,layered N-doped graphitic carbon nitride(g-C_(3)N_(4))porous nanosheets were successfully prepared by mixing the precursor of N,N-dimethylformamide(DMF)and urea through a simple one-step thermal copolymerization method.The doped-N plays a significant role in modifying the chemical and electronic structure of g-C_(3)N_(4),which can decrease the migration pathway of the charges and suppress the recombination of the photogenerated carriers based on experimental characterization data and the density functional theory(DFT)calculation results.Through nanostructure engineering design,the as-prepared photocatalyst exhibits promoted specific surface area and enhanced light absorption capacity.Consequently,the as-prepared N-doped porous g-C_(3)N_(4) nanosheets yield about 14 times higher H_(2) evolution rate than pristine g-C_(3)N_(4) nanosheets under visible light irradiation.The present study provides a simple and convenient method of nanostructure engineering for the synthesis of modified g-C_(3)N_(4) with excellent photocatalytic activity to meet the sustainable demand of energy.展开更多
Few-layer graphitic carbon nitride （g-C-N-） nanosheets were fabricated and utilized as a saturable absorber for mode-locking in an Er-doped fiber laser with net normal dispersion. Tile g-CaN,-/polyvinyl alcohol （PV...Few-layer graphitic carbon nitride （g-C-N-） nanosheets were fabricated and utilized as a saturable absorber for mode-locking in an Er-doped fiber laser with net normal dispersion. Tile g-CaN,-/polyvinyl alcohol （PVA） hybrid-film-based saturable absorber has a modulation depth of 4.01% and a saturation intensity of 7.5 MW/cm2. By integrating g-C3N4-PVA mode-locker into the laser cavity, a mode-locked operation could be obtained. The achieved mode-locking pulse centered at 1530.3 nm has a pulse width of 530 ps. Its repetition rate is 40.8 MHz, and the corresponding signal-to-noise ratio is about 55 dB.展开更多
基金supported by the Natural Science Foundation of China(Nos.51862024 and 51962023)the Key Research and Development Program of Jiangxi Province(No.20203BBE53066).
文摘Due to its larger ionic radius,further studies are needed before graphite can be used as an anode for sodium/potassium-ion batteries(SIBs/KIBs).It is believed that doping and increasing the layer spacing can improve the Na+/K+storage.Herein,S/N co-doped graphite nanosheets(GNS)with an enlarged interlayer spacing of 0.39 nm were prepared via exfoliation with three-roll milling(TRM)combined with thiourea heated at different temperatures.This method generates abundant defects and active sites for GNS,as well as facilitates rapid access and transport of electrolytes and electrons/ions.The electrochemical results show that the S/N-doped GNS exfoliated 15 times and heated at 600°C(SNGNS15-600)with thiourea as the electrode delivers a discharge capacity of 94 mAh g–1 over 6000 cycles at 10 A g–1 with an enhanced rate capability and stable performance for application in SIBs.Calculations using density functional theory show that the increased interlayer spacing by TRM and S,N co-doping enhances the adsorption energies of Na+on graphite,thus improving the Na+storage.As the anode for KIBs,the SNGNS15-600 electrode has a capacity of 142 mAh g–1 after 5000 cycles at 0.5 A g–1.This study provides an essential theoretical basis for the effective exfoliation of layered graphite-based materials and their applications in energy storage.
基金the National Natural Science Foundation of China(No.51972045)the Fundamental Research Funds for the Chinese Central Universities,China(No.ZYGX2019J025)。
文摘For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.
基金financially supported by Wuxi Municipal Bureau on Science and Technology,China(Wuxi 530 project,20130529010040)Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(SJCX180734)。
文摘Graphite nanosheets with the average thicknesses ranging from 24.4 to 48.9 nm were prepared with the use of expanded graphite as the raw material by sand milling in deionized water,anhydrous ethanol,glycerol,and 1,4-butanediol,respectively.Anhydrous ethanol favored the formation of graphite nanosheets with a smaller average thickness.When the graphite nanosheets with the content of 2 wt%were added in lithium-based grease,the average friction coefficient decreased by 27%as compared with the pure lithium-based grease.The weld point and load wear index were 1.6 and 1.4 times those of the pure lithium-based grease,respectively.The tribological properties of the graphite nanosheet-containing lithium-based grease were comparable with those of the graphene-containing lithium-based grease.
基金This work was supported by the National Science Foundation of China(51772152,51702129,51572114,51972150,21908110,and 51902161)Fundamental Research Funds for the Central Universities(30919011269,30919011110,and 1191030558)+3 种基金Y.W.thanks the Key University Science Research Project of Jiangsu province(16KJB430009)Y.Z.thanks for the support from the Postdoctoral Science Foundation(2018M630527)China Scholarship Council(201708320150)J.S.thanks the Natural Science Foundation of Jiangsu Province(BK20190479,1192261031693).
文摘Graphitic carbon nitride(g-C3N4)-based photocatalysts have shown great potential in the splitting of water.However,the intrinsic drawbacks of g-C3N4,such as low surface area,poor diffusion,and charge separation efficiency,remain as the bottleneck to achieve highly efficient hydrogen evolution.Here,a hollow oxygen-incorporated g-C3N4 nanosheet(OCN)with an improved surface area of 148.5 m2 g^−1 is fabricated by the multiple thermal treatments under the N2/O2 atmosphere,wherein the C–O bonds are formed through two ways of physical adsorption and doping.The physical characterization and theoretical calculation indicate that the O-adsorption can promote the generation of defects,leading to the formation of hollow morphology,while the O-doping results in reduced band gap of g-C3N4.The optimized OCN shows an excellent photocatalytic hydrogen evolution activity of 3519.6μmol g^−1 h^−1 for~20 h,which is over four times higher than that of g-C3N4(850.1μmol g^−1 h^−1)and outperforms most of the reported g-C3N4 catalysts.
基金the National Natural Science Foundation of China (22178120)Guangdong Natural Science Funds for Distinguished Young Scholar (2017A030306022)Guangzhou Technology Project (202002030164)。
文摘By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.
基金supported by the National Natural Science Foundation of China(no.22072015).
文摘The development of efficient electrocatalysts from Earth-abundant elements for the oxygen evolution reaction (OER) is highly desired.Here,we report the electrodeposition of a NiCo layered double hydroxide nanosheet array on graphite felt (NiCo LDHs/GF) as a 3D OER electrocatalyst.Such NiCo LDHs/GF exhibits superior electrocatalytic activity with the need for an overpotential of 249 mV to drive a current density of 20 mA cm^(-2) in 1.0 M KOH.It also shows strong long-term electrochemical durability with its activity being maintained for at least 24 h.
基金supported by the Key Research and Development Project of Hubei Province(no.2020BBB068)the Nature Science Foundation of Hubei Province(no.2020CFB400 and no.2021CFB218)+1 种基金the Central Committee Guides Local Science and Technology Development Special Project of Hubei Province(no.2019ZYYD059)the National Natural Science Foundation of China(no.52102111).
文摘Graphitic carbon nitride(g-C_(3)N_(4))nanosheets exfoliated from their bulk-sized counterparts are limited by a quantum size effect-induced widened bandgap.In this work,an(NH_(4))_(2)S_(2)O_(8)(APS)induced thermal exfoliation approach is introduced to fabricate O-doped g-C_(3)N_(4)nanosheets(OCNs).During this calcination process,the thermal decomposition products(NH_(3)and H_(2)SO_(4))from APS not only efficiently promote delamination,but also introduce O doping into the g-C_(3)N_(4)structure,realizing the synchronization control of the electronic structure and morphology.
基金The National Natural Science Foundation of China(No.21906072)Natural Science Foundation of Jiangsu Province(BK20190982)+1 种基金Doctoral Scientific Research Foundation of Jiangsu University of Science and Technology(China)(1062931806 and 1142931803)Science and Technology Research Project of Henan Province(202102210055).
文摘In this work,layered N-doped graphitic carbon nitride(g-C_(3)N_(4))porous nanosheets were successfully prepared by mixing the precursor of N,N-dimethylformamide(DMF)and urea through a simple one-step thermal copolymerization method.The doped-N plays a significant role in modifying the chemical and electronic structure of g-C_(3)N_(4),which can decrease the migration pathway of the charges and suppress the recombination of the photogenerated carriers based on experimental characterization data and the density functional theory(DFT)calculation results.Through nanostructure engineering design,the as-prepared photocatalyst exhibits promoted specific surface area and enhanced light absorption capacity.Consequently,the as-prepared N-doped porous g-C_(3)N_(4) nanosheets yield about 14 times higher H_(2) evolution rate than pristine g-C_(3)N_(4) nanosheets under visible light irradiation.The present study provides a simple and convenient method of nanostructure engineering for the synthesis of modified g-C_(3)N_(4) with excellent photocatalytic activity to meet the sustainable demand of energy.
基金supported by the National Natural Science Foundation of China(No.61575011)the Key Project of the National Natural Science Foundation of China(No.61235010)the Promotion Project of Beijing Municipal Institutions and Science and Technology Foundation(No.ykj-2017-00217)
文摘Few-layer graphitic carbon nitride （g-C-N-） nanosheets were fabricated and utilized as a saturable absorber for mode-locking in an Er-doped fiber laser with net normal dispersion. Tile g-CaN,-/polyvinyl alcohol （PVA） hybrid-film-based saturable absorber has a modulation depth of 4.01% and a saturation intensity of 7.5 MW/cm2. By integrating g-C3N4-PVA mode-locker into the laser cavity, a mode-locked operation could be obtained. The achieved mode-locking pulse centered at 1530.3 nm has a pulse width of 530 ps. Its repetition rate is 40.8 MHz, and the corresponding signal-to-noise ratio is about 55 dB.
