Graphene nanosheets(GSs) were prepared from graphite oxide by thermal exfoliation method. The effect of thermal exfoliation temperature on the structure and supercapacitive performance of GSs has been investigated. Th...Graphene nanosheets(GSs) were prepared from graphite oxide by thermal exfoliation method. The effect of thermal exfoliation temperature on the structure and supercapacitive performance of GSs has been investigated. The results show that the GSs with pore sizes center around 4.0 nm. With an increase of thermal reduction temperature, the number of stacking layers and the structure disorder degree increase, while the oxygen-containing groups content, BET surface area,and electrical resistivity of GSs decrease. The results indicate that 673 K is the preferable thermal exfoliation temperature to acquire good supercapacitive performance. In this case, the GSs have the best supercapacitive performance(233.1 F g-1) in a 6 mol L-1KOH electrolyte. The prepared GSs at the preferable thermal exfoliation temperature have good rate performance and cycle stability.展开更多
MXene is a new 2D transition metal carbide possessing metallic conductivity and hydrophilic surfaces.It has drawn widespread attention as a potential material for electrode use.However,the applications of MXene are li...MXene is a new 2D transition metal carbide possessing metallic conductivity and hydrophilic surfaces.It has drawn widespread attention as a potential material for electrode use.However,the applications of MXene are limited by its property of low electrical capacity.In this paper,a novel MnO_(2)/MXene composite is prepared by electrostatic self-assembly.Firstly,delaminated MnO_(2)nanosheets are obtained through the intercalation delamination of multilayered H-MnO_(2)in a cationic Gemini surfactant(Gem)solution,leading to a positively charged surface.Then,the positive MnO_(2)nanosheets are assembled on negative MXene nanosheets through electrostatic self-assembly to form a MnO_(2)/MXene composite.The characterization results show that the MnO_(2)nanosheets are intimately assembled on the MXene nanosheets.As an electrode material,the MnO_(2)/MXene composite displays a specific capacitance of 340 F g^(−1)at 1 A g^(−1),which is three times the performance of an MXene electrode.In addition,the MnO_(2)/MXene electrode shows a high retention rate(90.3%retention at 10 A g^(−1))and good cycling life(87.6%of the initial specific capacitance is retained after 2000 cycles at 4 A g^(−1)).The properties of the proposed composite are attributed to the excellent conductivity of MXene and the high specific capacitance of MnO_(2).展开更多
The goal of material chemistry is to study the relationship among hierarchical structure,chemical reaction and precision preparation for materials,yet tracking pyrolysis process on multi-dimensional scale is still at ...The goal of material chemistry is to study the relationship among hierarchical structure,chemical reaction and precision preparation for materials,yet tracking pyrolysis process on multi-dimensional scale is still at primary stage.Here we propose packing mode analysis to understand evolution process in high temperature reaction.As a proof of concept,we first design a salan-ligated Mn3(Mn3(3-MeOsalophen)_(2)(Cl)_(2))cluster and pyrolyze it under an inert atmosphere directly to a mixed valence MnOx embedded in a porous N-doped carbon skeleton(MnOx/C).Meanwhile,combining thermogravimetry-mass spectrometry(TG-MS)with other characterization techniques,its pyrolysis process is precisely tracked real-time and Mn^(2+)/Mn^(3+)ratios in the resulting materials are deduced,ensuring excellent electrochemical advantages.As a result,the as-preferred MnOVC-900 sample reaches 943 F/g at 1 A/g,maintaining good durability under 5,000 cycles with 90%retention.The highlight of packing mode analysis strategy in this work would provide a favorable approach to explore the potential relationship between structure and performance in the future.展开更多
A supercapacitor electrode has been fabricated from macroscopic porous MnO2 aerogels,and has demonstrated an enhanced specific capacitance,a high rate capability and excellent cycling durability.The improvement of sup...A supercapacitor electrode has been fabricated from macroscopic porous MnO2 aerogels,and has demonstrated an enhanced specific capacitance,a high rate capability and excellent cycling durability.The improvement of supercapacitive performance can be attributed to the macro interconnected channels in the aerogel structure,which can not only facilitate mass transfer and reduce dead volume,but also provide an additional benefit of relieving stress.展开更多
Efficient electrode material is crucial for energy conversion from renewable sources such as solar electricity. We present a method for preparation of carbon nanotubes （CNTs） with zeolitic imidazolate frameworks （Z...Efficient electrode material is crucial for energy conversion from renewable sources such as solar electricity. We present a method for preparation of carbon nanotubes （CNTs） with zeolitic imidazolate frameworks （ZIFs, e.g., ZIF-8） via an in situ pyrolysis process. The resultant materials are completely new carbon composites with desirable hierarchical porosity and nitrogen-doped features. Electron microscopy images show that CNTs with small external diameters enable more uniform dispersion of ZlF-8-derived carbons, subsequently yielding a unique hierarchically porous structure. Such carbon shows superior activity in oxygen reduction reaction （ORR） and high performance of supercapacitance, making it a valu- able metal-flee electrode material and a competent alternative to the state-of-the-art Pt/C catalyst. The electrocatalytic performance of CNTs can be dramatically improved by the incorporation of ZIF-8-derived carbons, which is attributed to the combination of good conductivity, abundant accessible dopant species, as well as proper porosity. Our method offers a new avenue for constructing electrocatalysts by effective integration of ZlF-8-derived carbon and the CNTs skeleton.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41272051)the Doctor Foundation of Southwest University of Science and Technology (Grant No. 11ZX7135)
文摘Graphene nanosheets(GSs) were prepared from graphite oxide by thermal exfoliation method. The effect of thermal exfoliation temperature on the structure and supercapacitive performance of GSs has been investigated. The results show that the GSs with pore sizes center around 4.0 nm. With an increase of thermal reduction temperature, the number of stacking layers and the structure disorder degree increase, while the oxygen-containing groups content, BET surface area,and electrical resistivity of GSs decrease. The results indicate that 673 K is the preferable thermal exfoliation temperature to acquire good supercapacitive performance. In this case, the GSs have the best supercapacitive performance(233.1 F g-1) in a 6 mol L-1KOH electrolyte. The prepared GSs at the preferable thermal exfoliation temperature have good rate performance and cycle stability.
基金supported by the research funds for the National Natural Science Foundation of China(21606081).
文摘MXene is a new 2D transition metal carbide possessing metallic conductivity and hydrophilic surfaces.It has drawn widespread attention as a potential material for electrode use.However,the applications of MXene are limited by its property of low electrical capacity.In this paper,a novel MnO_(2)/MXene composite is prepared by electrostatic self-assembly.Firstly,delaminated MnO_(2)nanosheets are obtained through the intercalation delamination of multilayered H-MnO_(2)in a cationic Gemini surfactant(Gem)solution,leading to a positively charged surface.Then,the positive MnO_(2)nanosheets are assembled on negative MXene nanosheets through electrostatic self-assembly to form a MnO_(2)/MXene composite.The characterization results show that the MnO_(2)nanosheets are intimately assembled on the MXene nanosheets.As an electrode material,the MnO_(2)/MXene composite displays a specific capacitance of 340 F g^(−1)at 1 A g^(−1),which is three times the performance of an MXene electrode.In addition,the MnO_(2)/MXene electrode shows a high retention rate(90.3%retention at 10 A g^(−1))and good cycling life(87.6%of the initial specific capacitance is retained after 2000 cycles at 4 A g^(−1)).The properties of the proposed composite are attributed to the excellent conductivity of MXene and the high specific capacitance of MnO_(2).
基金supported by the National Natural Science Fund for Distinguished Young Scholars(No.21525101)the National Natural Science Foundation of China(NSFC)(No.21805074)+1 种基金the BAGUI talent program(No.2019AC26001)the NSF of Guangxi(NSFGX,No.2017GXNSFDA198040).
文摘The goal of material chemistry is to study the relationship among hierarchical structure,chemical reaction and precision preparation for materials,yet tracking pyrolysis process on multi-dimensional scale is still at primary stage.Here we propose packing mode analysis to understand evolution process in high temperature reaction.As a proof of concept,we first design a salan-ligated Mn3(Mn3(3-MeOsalophen)_(2)(Cl)_(2))cluster and pyrolyze it under an inert atmosphere directly to a mixed valence MnOx embedded in a porous N-doped carbon skeleton(MnOx/C).Meanwhile,combining thermogravimetry-mass spectrometry(TG-MS)with other characterization techniques,its pyrolysis process is precisely tracked real-time and Mn^(2+)/Mn^(3+)ratios in the resulting materials are deduced,ensuring excellent electrochemical advantages.As a result,the as-preferred MnOVC-900 sample reaches 943 F/g at 1 A/g,maintaining good durability under 5,000 cycles with 90%retention.The highlight of packing mode analysis strategy in this work would provide a favorable approach to explore the potential relationship between structure and performance in the future.
基金supported by the National Natural Science Foundation of China(NSFC,21471067,51402121,and 51375204)Jilin Provincial Science&Technology Department(20140520163JH and 20140101056JC)Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry.
文摘A supercapacitor electrode has been fabricated from macroscopic porous MnO2 aerogels,and has demonstrated an enhanced specific capacitance,a high rate capability and excellent cycling durability.The improvement of supercapacitive performance can be attributed to the macro interconnected channels in the aerogel structure,which can not only facilitate mass transfer and reduce dead volume,but also provide an additional benefit of relieving stress.
基金supported by the Award Program for Fujian Minjiang Scholar Professorshipthe National Natural Science Foundation of China (21571035)
文摘Efficient electrode material is crucial for energy conversion from renewable sources such as solar electricity. We present a method for preparation of carbon nanotubes （CNTs） with zeolitic imidazolate frameworks （ZIFs, e.g., ZIF-8） via an in situ pyrolysis process. The resultant materials are completely new carbon composites with desirable hierarchical porosity and nitrogen-doped features. Electron microscopy images show that CNTs with small external diameters enable more uniform dispersion of ZlF-8-derived carbons, subsequently yielding a unique hierarchically porous structure. Such carbon shows superior activity in oxygen reduction reaction （ORR） and high performance of supercapacitance, making it a valu- able metal-flee electrode material and a competent alternative to the state-of-the-art Pt/C catalyst. The electrocatalytic performance of CNTs can be dramatically improved by the incorporation of ZIF-8-derived carbons, which is attributed to the combination of good conductivity, abundant accessible dopant species, as well as proper porosity. Our method offers a new avenue for constructing electrocatalysts by effective integration of ZlF-8-derived carbon and the CNTs skeleton.
