Porous heteroatom-doped carbon materials exhibit promising electrochemical applications because of tunable porous structure and doping heteroatom-induced charge redistribution.Nevertheless,it is still a great challeng...Porous heteroatom-doped carbon materials exhibit promising electrochemical applications because of tunable porous structure and doping heteroatom-induced charge redistribution.Nevertheless,it is still a great challenge to develop porous heteroatom-doped carbon materials with both high-content active heteroatom species and facilitated diffusion route.Herein,we report a bowl-shaped nitrogen and oxygen dual-doping carbon(N,O-doped carbon)material based on low-temperature defluorination pyrolysis and alkali-etched activation of 3-fluorophenol-3-amino-4-hydroxypyridine-formaldehyde co-condensed resin and its excellent supercapacitance.This low-temperature thermal treatment strategy ensures high-content pyrrolic nitrogen(4.6 at.%)and oxygen species(15.9 at.%)to avoid high-temperature treatment-induced heteroatom loss and undesired configuration conversion.In these processes,the defluorination pyrolysis promotes the transformation from the resin to carbon material to some extent,and KOH activation also promotes the ordered arrangement of 002 planes,which together assure the appropriate conductivity of the final microporous carbon material.More importantly,KOH-etched activation partially removes an un-stable nano/microscale domain of the intermediate carbon microspheres to form a unique bowl-shaped structure extremely facilitating the diffusion of the substitutes and/or electrolyte ions.As expected,N,O-doped carbon material displays a remarkable specific capacitance of 486.4 F g^(−1)at 1 A g^(−1)with nitro-gen/oxygen species-dependant pseudocapacitance and good electrochemical durability.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
Capacitance is generally determined by the porous microstructure,electron conduction and the synergy effect of active sites in the porous electrode.In this work,we grew centimeter-scale metallic porous GaN single crys...Capacitance is generally determined by the porous microstructure,electron conduction and the synergy effect of active sites in the porous electrode.In this work,we grew centimeter-scale metallic porous GaN single crystals with conductivity up to 18 S/cm at room temperature.The Cu-catecholates(Cu–CAT)nanowire arrays were grown on porous GaN single crystal to form porous single-crystalline electrode with enhanced supercapacitor performance.The Cu–CAT/GaN single crystalline electrode exhibits specific capacitance of 216 F/g and normalized capacitance of 40μF/cm^(2).After 5000 cycles,it retains 80%of its initial capacitance.The porous single-crystalline GaN electrode has high porosity and excellent conductivity showing high surface capacitance.展开更多
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
The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrotherma...The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrothermal method, while large-scale ZnCoOnanowires arrays homogeneously aligned and separated adequately on Ni foam coated with graphene. This ZnCoOnanowire structure exhibited superior supercapacitors properties. The excellent supercapacitors were mainly attributed to the large specific surface and the porosity on the nanowires which promoted the electrons and ions transportation. In addition, graphene improved conductivity of substrate for current collecting.展开更多
A novel bimetallic Ni/Co-based metal-organic framework(Ni/Co-MOF) was successfully synthesized via a simple solvothermal method, and used as electrode material for high performance supercapacitors. After doping of Co ...A novel bimetallic Ni/Co-based metal-organic framework(Ni/Co-MOF) was successfully synthesized via a simple solvothermal method, and used as electrode material for high performance supercapacitors. After doping of Co element, the Ni/Co-MOF materials retain the original crystalline topology structure of Ni_3(BTC)_2·12H_2O.The as-obtained Ni/Co-MOF demonstrates an excellent specific capacitance of 1067 and 780 F/g at current density of 1 and 10 A/g, respectively, and can also retain 68.4% of the original capacitance after 2500 cycles. These results suggest that bimetallic Ni/Co-based MOFs are promising materials for the next generation supercapacitance,owing to their excellent electrochemical performance. The synthetic procedure can be applied to synthesize other bimetallic MOFs and enhance their conductive property.展开更多
Molybdenum oxide(MoO_(3)), with superior features of multi-electrochemical states, high theoretical capacitance, and low cost, is a desirable supercapacitor electrode material but suffers from low conductivity and ins...Molybdenum oxide(MoO_(3)), with superior features of multi-electrochemical states, high theoretical capacitance, and low cost, is a desirable supercapacitor electrode material but suffers from low conductivity and insufficient active sites. The MoO_(3) capacitance can be largely amplified by introducing oxygen(O) vacancies, but the mechanisms at the atomic scale are still ambiguous.Herein, O vacancies are created at the O2 and O3 sites in the MoO_(3) nanobelts by carbonization to maximize the supercapacitance in the MoO_(2.39). The supercapacitive storage is mainly ascribed to the proton adsorption at the O1 sites to create Mo–OH, leading to an expansion of the interlayer spacing along the lattice B-axis. Roughly 98% of the initial supercapacitance is retained after 1000 cycles,due to the reversible change in the interlayer spacing. Our results provide an insight into the oxygen deficiency-related mechanisms of the supercapacitive performance at the atomic scale and devise a facile method to enhance the supercapacitance for energy storage and conversion.展开更多
Nanocrystallines Co3O4 with the particle di-ameter of 3 nm are prepared and tested as active electrode material for an electrochemical supercapacitor. The results of characterization indicate that the grain size of th...Nanocrystallines Co3O4 with the particle di-ameter of 3 nm are prepared and tested as active electrode material for an electrochemical supercapacitor. The results of characterization indicate that the grain size of this mate-rial is very small; the specific surface area is very high (192 m2/g); the distributions of pore diameter are desirable and effective; furthermore, the agglomeration problem among small particles was solved to a certain extent. The electro-chemical tests show that the electrode prepared with the Co3O4 exhibits distinct characteristic of capacitance and very high specific capacitance of 365—401 F/g. Additionally, the main attribute of capacitance, namely supercapacitance, was also testified.展开更多
High-temperature （150-220 ℃） growth leads to the formation of some peptide nanotube/microtube （NT/MT） arrays but the NTs/MTs exhibit closed ends, irreversible phase modification and eliminations of piezoelectric ...High-temperature （150-220 ℃） growth leads to the formation of some peptide nanotube/microtube （NT/MT） arrays but the NTs/MTs exhibit closed ends, irreversible phase modification and eliminations of piezoelectric and hydrophilic properties. Here we demonstrate the fabrication of unidirectionally aligned and stable diphenylalanine NT/MT arrays with centimeter scale area at room temperature by utilizing an external electric field. The interactions between the applied electric field and dipolar electric field on the NTs and surface positive charges are responsible for the formation. The unidirectionally aligned MT array exhibits a supercapacitance of 1,000 μF·cm^-2 at a scanning rate of 50 mV·s^-1; this is much larger than the values reported previously in peptide NT/MT arrays.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
基金the National Natural Science Foundation of China(No.52202048)the Hebei Natural Science Foundation(Nos.E2022203082 and B2021203012)the Department of Education of Hebei Province(No.QN2021140).
文摘Porous heteroatom-doped carbon materials exhibit promising electrochemical applications because of tunable porous structure and doping heteroatom-induced charge redistribution.Nevertheless,it is still a great challenge to develop porous heteroatom-doped carbon materials with both high-content active heteroatom species and facilitated diffusion route.Herein,we report a bowl-shaped nitrogen and oxygen dual-doping carbon(N,O-doped carbon)material based on low-temperature defluorination pyrolysis and alkali-etched activation of 3-fluorophenol-3-amino-4-hydroxypyridine-formaldehyde co-condensed resin and its excellent supercapacitance.This low-temperature thermal treatment strategy ensures high-content pyrrolic nitrogen(4.6 at.%)and oxygen species(15.9 at.%)to avoid high-temperature treatment-induced heteroatom loss and undesired configuration conversion.In these processes,the defluorination pyrolysis promotes the transformation from the resin to carbon material to some extent,and KOH activation also promotes the ordered arrangement of 002 planes,which together assure the appropriate conductivity of the final microporous carbon material.More importantly,KOH-etched activation partially removes an un-stable nano/microscale domain of the intermediate carbon microspheres to form a unique bowl-shaped structure extremely facilitating the diffusion of the substitutes and/or electrolyte ions.As expected,N,O-doped carbon material displays a remarkable specific capacitance of 486.4 F g^(−1)at 1 A g^(−1)with nitro-gen/oxygen species-dependant pseudocapacitance and good electrochemical durability.
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.
基金supported by the National Key Research and Development Program of China(2017YFA0700102)Natural Science Foundation of China(91845202)+1 种基金Dalian National Laboratory for Clean Energy(DNL180404)Strategic Priority Research Program of Chinese Academy of Sciences(XDB2000000)。
文摘Capacitance is generally determined by the porous microstructure,electron conduction and the synergy effect of active sites in the porous electrode.In this work,we grew centimeter-scale metallic porous GaN single crystals with conductivity up to 18 S/cm at room temperature.The Cu-catecholates(Cu–CAT)nanowire arrays were grown on porous GaN single crystal to form porous single-crystalline electrode with enhanced supercapacitor performance.The Cu–CAT/GaN single crystalline electrode exhibits specific capacitance of 216 F/g and normalized capacitance of 40μF/cm^(2).After 5000 cycles,it retains 80%of its initial capacitance.The porous single-crystalline GaN electrode has high porosity and excellent conductivity showing high surface capacitance.
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.
文摘The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrothermal method, while large-scale ZnCoOnanowires arrays homogeneously aligned and separated adequately on Ni foam coated with graphene. This ZnCoOnanowire structure exhibited superior supercapacitors properties. The excellent supercapacitors were mainly attributed to the large specific surface and the porosity on the nanowires which promoted the electrons and ions transportation. In addition, graphene improved conductivity of substrate for current collecting.
基金financially supported by the National Natural Science Foundation of China(Nos. 21306026, 21576054, 51678160)the Scientific Project of Guangdong Province(Nos. 2014A010106030,2014A010105041,2016A010104017, 2016B020241003)the Foundation of Higher Education of Guangdong Province(No. 2015KTSCX027)
文摘A novel bimetallic Ni/Co-based metal-organic framework(Ni/Co-MOF) was successfully synthesized via a simple solvothermal method, and used as electrode material for high performance supercapacitors. After doping of Co element, the Ni/Co-MOF materials retain the original crystalline topology structure of Ni_3(BTC)_2·12H_2O.The as-obtained Ni/Co-MOF demonstrates an excellent specific capacitance of 1067 and 780 F/g at current density of 1 and 10 A/g, respectively, and can also retain 68.4% of the original capacitance after 2500 cycles. These results suggest that bimetallic Ni/Co-based MOFs are promising materials for the next generation supercapacitance,owing to their excellent electrochemical performance. The synthetic procedure can be applied to synthesize other bimetallic MOFs and enhance their conductive property.
基金financially supported by the Hong Kong Baptist University(No.RMGS-2019-1-03A)。
文摘Molybdenum oxide(MoO_(3)), with superior features of multi-electrochemical states, high theoretical capacitance, and low cost, is a desirable supercapacitor electrode material but suffers from low conductivity and insufficient active sites. The MoO_(3) capacitance can be largely amplified by introducing oxygen(O) vacancies, but the mechanisms at the atomic scale are still ambiguous.Herein, O vacancies are created at the O2 and O3 sites in the MoO_(3) nanobelts by carbonization to maximize the supercapacitance in the MoO_(2.39). The supercapacitive storage is mainly ascribed to the proton adsorption at the O1 sites to create Mo–OH, leading to an expansion of the interlayer spacing along the lattice B-axis. Roughly 98% of the initial supercapacitance is retained after 1000 cycles,due to the reversible change in the interlayer spacing. Our results provide an insight into the oxygen deficiency-related mechanisms of the supercapacitive performance at the atomic scale and devise a facile method to enhance the supercapacitance for energy storage and conversion.
文摘Nanocrystallines Co3O4 with the particle di-ameter of 3 nm are prepared and tested as active electrode material for an electrochemical supercapacitor. The results of characterization indicate that the grain size of this mate-rial is very small; the specific surface area is very high (192 m2/g); the distributions of pore diameter are desirable and effective; furthermore, the agglomeration problem among small particles was solved to a certain extent. The electro-chemical tests show that the electrode prepared with the Co3O4 exhibits distinct characteristic of capacitance and very high specific capacitance of 365—401 F/g. Additionally, the main attribute of capacitance, namely supercapacitance, was also testified.
基金Acknowledgements This work was supported by the National Basic Research Programs of China under Grants Nos. 2011CB922102 and 2013CB932901 and the National Natural Science Foundation of China （Nos. 11374141 and 21203098 ）.
文摘High-temperature （150-220 ℃） growth leads to the formation of some peptide nanotube/microtube （NT/MT） arrays but the NTs/MTs exhibit closed ends, irreversible phase modification and eliminations of piezoelectric and hydrophilic properties. Here we demonstrate the fabrication of unidirectionally aligned and stable diphenylalanine NT/MT arrays with centimeter scale area at room temperature by utilizing an external electric field. The interactions between the applied electric field and dipolar electric field on the NTs and surface positive charges are responsible for the formation. The unidirectionally aligned MT array exhibits a supercapacitance of 1,000 μF·cm^-2 at a scanning rate of 50 mV·s^-1; this is much larger than the values reported previously in peptide NT/MT arrays.
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.
