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 micr...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.展开更多
Mo2C was prepared by microwave plasma chemical vapor deposition(MPCVD)technique with the power of 800 W and pressure of 18 kPa.Compared with traditional preparation methods,MPCVD has faster growth rate and higher puri...Mo2C was prepared by microwave plasma chemical vapor deposition(MPCVD)technique with the power of 800 W and pressure of 18 kPa.Compared with traditional preparation methods,MPCVD has faster growth rate and higher purity of the products.The influence of growth time on the morphology and structure of Mo_(2)C was characterized by X-ray diffraction and Scanning Electron Microscopy.The photocatalytic performance of Mo_(2)C was tested.It was found that Mo_(2)C had good photocatalytic performance and the 6 h sample had the highest photodegradation rate,indicating the great potential of Mo_(2)C as photocatalyst.展开更多
The low sulfur utilization and fast capacity fading resulting from the sluggish redox reaction and abominable polysulfides shuttle greatly hinder the practical applications of lithium-sulfur(Li-S) batteries.Herein, we...The low sulfur utilization and fast capacity fading resulting from the sluggish redox reaction and abominable polysulfides shuttle greatly hinder the practical applications of lithium-sulfur(Li-S) batteries.Herein, we develop a facile "in-situ growth" method to decorate ultra-small Mo2 C nanoparticles(USMo2 C) on the surface of Ketjen Black(KB) to functionalize the commercial polypropylene(PP) separators,which can accelerate the redox kinetics of lithium polysulfides conversion and effectively increase the utilization of sulfur for Li-S batteries. Importantly, the US-Mo2 C nanoparticles have abundant sites for chemical adsorption towards polysulfides and the conductive carbon networks of KB have cross-linked pore channels, which can promote electron transport and provide physical barrier and volume expansion space for polysulfides. Due to the combined effects of the US-Mo2 C and KB, Li-S cells employing the multifunctional PP separators modified with KB/US-Mo2 C composite(KB/US-Mo2 C@PP) exhibit a high specific capacity(1212.8 mAh g^(-1) at 0.2 C), and maintain a reversible capacity of 1053.3 m Ah g^(-1) after 100 cycles.More importantly, the KB/US-Mo2 C@PP cells with higher sulfur mass loading of 4.9 mg cm^(-2) have superb areal capacity of 2.3 mAh cm^(-2). This work offers a novel and promising perspective for high-performance Li-S batteries from both the shuttle effect and the complex polysulfides conversion.展开更多
With OLYMPUS PMG3 metallograph, an abnormal three layer gradient structure ,i.e. coarse grain zone, binder enrichment zone and normal structure zone from the surface to the inner, was observed in Cr 3C 2 based cemente...With OLYMPUS PMG3 metallograph, an abnormal three layer gradient structure ,i.e. coarse grain zone, binder enrichment zone and normal structure zone from the surface to the inner, was observed in Cr 3C 2 based cemented carbide. In the binder enrichment zone, three different shapes of anomalous coarse carbides were observed. It is shown that the transverse rupture strength can be raised remarkably, up 20.7% from the alloy with abnormal gradient structure by removing the abnormal gradient structure. It is suggested that the abnormal gradient structure in the surface, especially the anomalous coarse carbides in the binder enrichment zone is the main reasons for the lower strength.展开更多
The selective cleavage of C-O and C-C is facing a challenge in the field of catalysis.In the present work,we studied the influence of doped Ni on the structure and electronic properties,as well as the selective C-O/C-...The selective cleavage of C-O and C-C is facing a challenge in the field of catalysis.In the present work,we studied the influence of doped Ni on the structure and electronic properties,as well as the selective C-O/C-C bond cleavages in the hydrodeoxygenation of palmitic acid over Ni-Mo_(2)C catalyst.The catalytic activity on Ni doped Mo_(2)C with TOF of 6.9×10^(3)h^(-1)is much superior to intrinsic Mo_(2)C catalyst,which is also higher than most noble metal catalysts.Structurally,the doped Ni raises the active particle dispersion and the coordination numbers of Mo species(Mo-C and Mo-O),improves the graphitization degree to promote the electron transfer,and increases the amount of Lewis and Br?nsted acid,which are responsible for the excellent hydrodeoxygenation performance.The Ni promotes simultaneously C-O and C-C bonds cleavage to produce pentadecane and hexadecane owing to the increase of electron-rich Mo sites after Ni doping.These findings contribute to the understanding of the nature of Ni-doped Mo_(2)C on the roles as catalytic active sites for C-O and C-C bonds cleavage.展开更多
基金supported by the China Postdoctoral Science Foundation(No.2021MD703944)the Fund of Science and Technology on Near-Surface Detection Laboratory(No.6142414211808)+1 种基金the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2021ZR06)the National Natural Science Foundation of China(No.21776053)。
文摘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.
基金Hubei Provincial Department of Education(Q20201512)。
文摘Mo2C was prepared by microwave plasma chemical vapor deposition(MPCVD)technique with the power of 800 W and pressure of 18 kPa.Compared with traditional preparation methods,MPCVD has faster growth rate and higher purity of the products.The influence of growth time on the morphology and structure of Mo_(2)C was characterized by X-ray diffraction and Scanning Electron Microscopy.The photocatalytic performance of Mo_(2)C was tested.It was found that Mo_(2)C had good photocatalytic performance and the 6 h sample had the highest photodegradation rate,indicating the great potential of Mo_(2)C as photocatalyst.
基金financially supported by the National Natural Science Foundation of China for Innovative Research Groups (No. 51621002)the National Key Research and Development Program of China (Grant No. 2016YFA0203700)+5 种基金NSFC (Grant No 51672083)Program of Shanghai Academic/Technology Research Leader (18XD1401400)Basic Research Program of Shanghai (17JC1404702)Leading talents in Shanghai in 2018The Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, the 111 project (B14018)The Fundamental Research Funds for Central Universities (222201718002)。
文摘The low sulfur utilization and fast capacity fading resulting from the sluggish redox reaction and abominable polysulfides shuttle greatly hinder the practical applications of lithium-sulfur(Li-S) batteries.Herein, we develop a facile "in-situ growth" method to decorate ultra-small Mo2 C nanoparticles(USMo2 C) on the surface of Ketjen Black(KB) to functionalize the commercial polypropylene(PP) separators,which can accelerate the redox kinetics of lithium polysulfides conversion and effectively increase the utilization of sulfur for Li-S batteries. Importantly, the US-Mo2 C nanoparticles have abundant sites for chemical adsorption towards polysulfides and the conductive carbon networks of KB have cross-linked pore channels, which can promote electron transport and provide physical barrier and volume expansion space for polysulfides. Due to the combined effects of the US-Mo2 C and KB, Li-S cells employing the multifunctional PP separators modified with KB/US-Mo2 C composite(KB/US-Mo2 C@PP) exhibit a high specific capacity(1212.8 mAh g^(-1) at 0.2 C), and maintain a reversible capacity of 1053.3 m Ah g^(-1) after 100 cycles.More importantly, the KB/US-Mo2 C@PP cells with higher sulfur mass loading of 4.9 mg cm^(-2) have superb areal capacity of 2.3 mAh cm^(-2). This work offers a novel and promising perspective for high-performance Li-S batteries from both the shuttle effect and the complex polysulfides conversion.
文摘With OLYMPUS PMG3 metallograph, an abnormal three layer gradient structure ,i.e. coarse grain zone, binder enrichment zone and normal structure zone from the surface to the inner, was observed in Cr 3C 2 based cemented carbide. In the binder enrichment zone, three different shapes of anomalous coarse carbides were observed. It is shown that the transverse rupture strength can be raised remarkably, up 20.7% from the alloy with abnormal gradient structure by removing the abnormal gradient structure. It is suggested that the abnormal gradient structure in the surface, especially the anomalous coarse carbides in the binder enrichment zone is the main reasons for the lower strength.
基金financially supported by the National Natural Science Foundation of China(21972099)the Application Foundation Program of Sichuan Province(2021YJ0305)+1 种基金the 111 project(B17030).Shanghai Synchrotron Radiation Facility(SSRF)for XAS experiments and the support by the project from NPL of CAEP(2019BB08)。
文摘The selective cleavage of C-O and C-C is facing a challenge in the field of catalysis.In the present work,we studied the influence of doped Ni on the structure and electronic properties,as well as the selective C-O/C-C bond cleavages in the hydrodeoxygenation of palmitic acid over Ni-Mo_(2)C catalyst.The catalytic activity on Ni doped Mo_(2)C with TOF of 6.9×10^(3)h^(-1)is much superior to intrinsic Mo_(2)C catalyst,which is also higher than most noble metal catalysts.Structurally,the doped Ni raises the active particle dispersion and the coordination numbers of Mo species(Mo-C and Mo-O),improves the graphitization degree to promote the electron transfer,and increases the amount of Lewis and Br?nsted acid,which are responsible for the excellent hydrodeoxygenation performance.The Ni promotes simultaneously C-O and C-C bonds cleavage to produce pentadecane and hexadecane owing to the increase of electron-rich Mo sites after Ni doping.These findings contribute to the understanding of the nature of Ni-doped Mo_(2)C on the roles as catalytic active sites for C-O and C-C bonds cleavage.
