The mechanical and tribological properties of hot-pressed copper-based composites containing different amounts of graphene nanosheets（GNSs） are compared with those of copper-graphite（Gr） composites fabricated by t...The mechanical and tribological properties of hot-pressed copper-based composites containing different amounts of graphene nanosheets（GNSs） are compared with those of copper-graphite（Gr） composites fabricated by the same method.The results show that the Cu-GNSs composites exhibit higher relative density,microhardness and bending strength compared with Cu-Gr composites with the same volume fraction of GNSs and Gr.Moreover,the friction coefficients and wear rates reduce significantly by the addition of GNSs,whereas the limited impact on reducing friction and wear is found on graphite.The abrasive and delamination wear are the dominant wear mechanisms of the composites.It is believed that the superior mechanical and tribological performances of Cu-GNSs composites are attributed to the unique strengthening effect as well as the higher lubricating efficiency of graphene nanosheets compared with those of graphite,which demonstrates that GNS is an ideal filler for copper matrix composites,acting as not only an impactful lubricant but also a favorable reinforcement.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 solid-solution reaction between an alkali cation and an active host material is known as a singlephase redox mechanism,and it is typically accompanied by a continuous voltage change.It is distinct from the typical...The solid-solution reaction between an alkali cation and an active host material is known as a singlephase redox mechanism,and it is typically accompanied by a continuous voltage change.It is distinct from the typical alkali cation intercalation reaction at an equivalent site of the active host material,which exhibits a voltage plateau.Herein,we report an unusual solid-solution potassium-ion intercalation mechanism with a low-voltage plateau capacity on multilayered turbostratic graphene nanosheets(T-GNSs).Despite the disordered graphitic structure with a broad range of d-spacings(3.65–4.18À),the T-GNSs showed a reversible plateau capacity of~200 m A h g^(-1),which is higher than that of a well-ordered graphite nanoplate(~120 m A h g^(-1)).In addition,a sloping capacity of~220 m A h g^(-1)was delivered with the plateau capacity,and higher rate capabilities,better reversibility,and a more stable cycling performance were confirmed on the turbostratic microstructure.First-principles calculations suggest that the multitudinous lattice domains of the T-GNSs contain diverse intercalation sites with strong binding energies,which could be the origin of the high-performance solid-solution potassium-ion intercalation behavior when the turbostratic graphene stacks have a d-spacing smaller than that of equilibrium potassium–graphite intercalation compounds(5.35À).展开更多
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
Covalently bonded bridging between different semiconductors is a remarkable approach to improve the transfer of charge carriers at interfaces.In this study,we designed a ternary heterojunction(MBG)combining of molybde...Covalently bonded bridging between different semiconductors is a remarkable approach to improve the transfer of charge carriers at interfaces.In this study,we designed a ternary heterojunction(MBG)combining of molybdenum diselenide(Mo Se_(2)),black phosphorus nanosheets(Bpn)and graphitic carbon nitride(GCN).Among this MBG of Mo Se_(2)/Bpn/GCN,(i)the covalently bonded bridging effect between Bpn/GCN facilitates directional charge carrier transfer,meanwhile(ii)a Z-scheme heterojunction is formed between Mo Se_(2)/GCN to enhance the separation of photogenerated carriers.Furthermore,(iii)this composite exhibits an increased absorption for visible light.Using this MBG,photocatalytic degradation of over 98%of moxifloxacin is achieved within 20 min,with O_(2)·-confirmed as the primary photocatalytic active species.These findings provide novel insights into the construction of efficient heterojunction by covalently bonded bridging.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
文摘The mechanical and tribological properties of hot-pressed copper-based composites containing different amounts of graphene nanosheets（GNSs） are compared with those of copper-graphite（Gr） composites fabricated by the same method.The results show that the Cu-GNSs composites exhibit higher relative density,microhardness and bending strength compared with Cu-Gr composites with the same volume fraction of GNSs and Gr.Moreover,the friction coefficients and wear rates reduce significantly by the addition of GNSs,whereas the limited impact on reducing friction and wear is found on graphite.The abrasive and delamination wear are the dominant wear mechanisms of the composites.It is believed that the superior mechanical and tribological performances of Cu-GNSs composites are attributed to the unique strengthening effect as well as the higher lubricating efficiency of graphene nanosheets compared with those of graphite,which demonstrates that GNS is an ideal filler for copper matrix composites,acting as not only an impactful lubricant but also a favorable reinforcement.
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Acknowledgements： This work was supported by the National Natural Science Foundation of China （No. 29875018）, the Natural Science Foundation of Gansu Province （No. 3ZS051-A25-050）, Science and Technology Tackle Key Problem Item of （No. 2GS064-A52-036-08）, Gansu Key Laboratory of Polymer Materials （No. ZD-04-14） and Environmental Protection Foundation of Gansu （No. GH2005-10）.
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 Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2019R1A2C1084836,and NRF-2021R1A4A2001403)supported by the KU-KIST School Program。
文摘The solid-solution reaction between an alkali cation and an active host material is known as a singlephase redox mechanism,and it is typically accompanied by a continuous voltage change.It is distinct from the typical alkali cation intercalation reaction at an equivalent site of the active host material,which exhibits a voltage plateau.Herein,we report an unusual solid-solution potassium-ion intercalation mechanism with a low-voltage plateau capacity on multilayered turbostratic graphene nanosheets(T-GNSs).Despite the disordered graphitic structure with a broad range of d-spacings(3.65–4.18À),the T-GNSs showed a reversible plateau capacity of~200 m A h g^(-1),which is higher than that of a well-ordered graphite nanoplate(~120 m A h g^(-1)).In addition,a sloping capacity of~220 m A h g^(-1)was delivered with the plateau capacity,and higher rate capabilities,better reversibility,and a more stable cycling performance were confirmed on the turbostratic microstructure.First-principles calculations suggest that the multitudinous lattice domains of the T-GNSs contain diverse intercalation sites with strong binding energies,which could be the origin of the high-performance solid-solution potassium-ion intercalation behavior when the turbostratic graphene stacks have a d-spacing smaller than that of equilibrium potassium–graphite intercalation compounds(5.35À).
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 the National Natural Science Foundation of China(No.52100076)the Fundamental Research Funds for the Central Universities(No.2023MS064)。
文摘Covalently bonded bridging between different semiconductors is a remarkable approach to improve the transfer of charge carriers at interfaces.In this study,we designed a ternary heterojunction(MBG)combining of molybdenum diselenide(Mo Se_(2)),black phosphorus nanosheets(Bpn)and graphitic carbon nitride(GCN).Among this MBG of Mo Se_(2)/Bpn/GCN,(i)the covalently bonded bridging effect between Bpn/GCN facilitates directional charge carrier transfer,meanwhile(ii)a Z-scheme heterojunction is formed between Mo Se_(2)/GCN to enhance the separation of photogenerated carriers.Furthermore,(iii)this composite exhibits an increased absorption for visible light.Using this MBG,photocatalytic degradation of over 98%of moxifloxacin is achieved within 20 min,with O_(2)·-confirmed as the primary photocatalytic active species.These findings provide novel insights into the construction of efficient heterojunction by covalently bonded bridging.
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.
