Shenzhen has extensive green construction experience as one of China’s new green development pilot cities.Shenzhen has experienced substantial economic growth as a result of the reform and opening up,but it has also ...Shenzhen has extensive green construction experience as one of China’s new green development pilot cities.Shenzhen has experienced substantial economic growth as a result of the reform and opening up,but it has also had to face the burden of urbanization problems and difficulties.This article looks at the history of green construction in Shenzhen and how the spirit of the city influenced it.The work then divides the procedure into two phases and examines the issues that arise.Suggestions for achieving the“Double Carbon”aim in the building industry are sought through this effort.展开更多
Cities generate more than 60%of carbon emissions and are the main battleground for achieving the target.However,there is no unified and standardized measurement methods of carbon emissions in cities.In this paper,we t...Cities generate more than 60%of carbon emissions and are the main battleground for achieving the target.However,there is no unified and standardized measurement methods of carbon emissions in cities.In this paper,we took Xi’an as an example and started by measuring carbon emissions with the new standards.Then,the decoupling of economic development from carbon emissions was studied according to the Tapio decoupling theory.Based on the generalized Divisia index method,the decoupling effort model was proposed to study the impact of carbon emission factors contributing to carbon reduction.The results show:(i)During the period 1995–2021,the carbon emissions of Xi’an increased rapidly,with an average annual growth rate of 6.06%,due to the accelerating pace of urbanization and industrialization.(ii)The energy consumption sector accounted for the largest share of carbon emissions,ranging from 77.38%to 89.46%.Xi’an’s energy structure is primarily based on fossil fuels,especially coal,which holds a significant proportion.To achieve the“double carbon”goal,it is crucial to reduce the dependence on fossil fuels.(iii)The 10th Five-Year Plan was in the state of“expansive coupling”,while other periods were in the“weak decoupling”state from the 9th to 14th Five-Year Plan periods.After the carbon peak year in the 15th Five-Year Plan,it would be in a state of“strong decoupling”.The agricultural production account was the first to achieve a“strong decoupling”state.(iv)The government of Xi’an made efforts to decouple,but these were not enough.Technological innovation played a crucial role in the carbon reduction of Xi’an,and was a key factor in achieving the“double carbon”goal.展开更多
ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experi...ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.展开更多
Among the many strategies to fabricate the silicon/carbon composite,yolk/double-shells structure can be regarded as an effective strategy to overcome the intrinsic defects of Si-based anode materials for Li-ion batter...Among the many strategies to fabricate the silicon/carbon composite,yolk/double-shells structure can be regarded as an effective strategy to overcome the intrinsic defects of Si-based anode materials for Li-ion batteries(LIBs).Hereon,a facile and inexpensive technology to prepare silicon/carbon composite with yolk/double-shells structure is proposed,in which the double buffering carbon shells are fabricated.The silicon/carbon nanoparticles with core-shell structure are encapsulated by SiO_(2)and external carbon layer,and it shows the yolk/double-shells structure via etching the SiO_(2)sacrificial layer.The multiply shells structure not only significantly improves the electrical conductivity of composite,but also effectively prevents the exposure of Si particles from the electrolyte composition.Meanwhile,the yolk/double-shells structure can provide enough space to accommodate the volume change of the electrode during charge/discharge process and avoid the pulverization of Si particles.Moreover,the as-prepared YDS-Si/C shows excellent performance as anode of LIBs,the reversible capacity is as high as 1066 mA h g^(-1) at the current density of 0.5 A g^(-1) after 200 cycles.At the same time,the YDS-Si/C has high capacity retention and good cyclic stability.Therefore,the unique architecture design of yolk/double-shells for Si/C composite provides an instructive exploration for the development of next generation anode materials of LIBs with high electrochemical performances and structural stability.展开更多
1 Introduction In recent years porous carbons have been widely used in many fields such as energy storage(Mc Creery,2008;Liu et al,2009;Ho et al,2014;Yang et al,2015),adsorption,wastewater treatment,air purification
Realizing “carbon peaking” and “carbon neutrality” is a major strategic decision made by China to coordinate domestic and international situations.In order to achieve the “double carbon” goal,it is also necessar...Realizing “carbon peaking” and “carbon neutrality” is a major strategic decision made by China to coordinate domestic and international situations.In order to achieve the “double carbon” goal,it is also necessary for relevant practitioners to actively put into practice to improve the participation of residents and advocate low carbon life while formulating the policy action plan.Community is an important place for human activities and one of the main spatial types of carbon emissions in cities.Doing a good job in planning energy conservation and emission reduction in the community plays an important role in achieving the “double carbon” goal.Through the analysis of classic low carbon community practice cases at home and abroad,6 planning and design methods for low carbon community are concluded,and the development status of low carbon community in China is reflected and summarized.展开更多
The double-activated porous carbons(DAPCs)with unique bimodal pore structure were prepared by activating commercial microporous carbon(CMCs) twice through KOH(double activation) at high temperature. The as-prepa...The double-activated porous carbons(DAPCs)with unique bimodal pore structure were prepared by activating commercial microporous carbon(CMCs) twice through KOH(double activation) at high temperature. The as-prepared DAPCs show larger surface area(833 m^2·g^-1),and the pores are composed of micropores(size of-1.8 nm) and mesopores(size of -4.5 nm). Such special hierarchical porous structures integrate the dual advantages of micropore and mesopore, having not only the high energy storage of the micropores but also the high-rate performance of the mesopores for supercapacitors(SCs).As a result, the optimized DAPCs-3-1 exhibits a high specific capacitance of 277 F·g^-1 at 1 A·g^-1, enhanced rate performance of 197 F·g^-1 at a high current density of 10 A·g^-1, and excellent cycling stability with 94.2% capacity retention after 10,000 cycles in the 1 mol·L^-1 Na2SO4 electrolyte. The facile double activation could be a promising method to prepare suitable porous carbons with exceptional electrochemical properties for SCs.展开更多
Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides(LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH(OLDH) in the ...Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides(LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH(OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction(XRD) and scanning electron microscopy(SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient(OP) and water vapor permeability coefficient(WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.展开更多
The effects of doubled carbon dioxide on rainfall responses to radiative processes of water clouds are investigated in this study.Two groups of two-dimensional cloud-resolving model sensitivity experiments with regard...The effects of doubled carbon dioxide on rainfall responses to radiative processes of water clouds are investigated in this study.Two groups of two-dimensional cloud-resolving model sensitivity experiments with regard to pre-summer heavy rainfall around the summer solstice and tropical rainfall around the winter solstice are conducted and their five-day averages over the model domain are analyzed.In the presence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the decrease associated with the enhanced atmospheric cooling to the increase associated with the enhanced infrared cooling as a result of the exclusion of radiative effects of water clouds.Doubled carbon dioxide leads to the reduction in tropical rainfall,caused by the removal of radiative effects of water clouds through the suppressed infrared cooling.In the absence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the increase associated with the strengthened atmospheric warming to the decrease associated with the weakened release of latent heat caused by the elimination of radiative effects of water clouds.The exclusion of radiative effects of water clouds increases tropical rainfall through the strengthened infrared cooling,which is insensitive to the change in carbon dioxide.展开更多
The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power s...The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehyde- cross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer-Emmett-Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.展开更多
Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe2...Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe2/rGO composite with both high porosity and large surface area. Double modification of MoSe2 nanosheets is realized in this composite by introducing a reduced graphene oxide (rGO) skeleton and outer carbon protective layer. The MoSe2 nanosheets are well wrapped by a carbon layer and also strongly anchored on the interconnected rGO network. As an anode in sodium ion batteries, the designed C-MoSe2/rGO composite delivers noticeably enhanced sodium ion storage, with a high specific capacity of 445 mAh-g-1 at 200 mA.g-1 after 350 cycles, and 228 mAh-g 1 even at 4 A.g-1; these values are much better than those of C-MoSe2 nanosheets (258 mAh.g-a at 200 mA-g-1 and 75 mAh-g-1 at 4 A.g-~). Additionally, the sodium ion storage mechanism is investigated well using ex situ X-ray diffraction and transmission electron microscopy methods. Our proposed electrode design protocol and sodium storage mechanism may pave the way for the fabrication of other high-performance metal diselenide anodes for electrochemical energy storage.展开更多
Polymeric nanoparticles(NPs)have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare function...Polymeric nanoparticles(NPs)have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly(divinyl benzene-co-maleic anhydride)NPs(PDVBMAH NPs)through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.展开更多
文摘Shenzhen has extensive green construction experience as one of China’s new green development pilot cities.Shenzhen has experienced substantial economic growth as a result of the reform and opening up,but it has also had to face the burden of urbanization problems and difficulties.This article looks at the history of green construction in Shenzhen and how the spirit of the city influenced it.The work then divides the procedure into two phases and examines the issues that arise.Suggestions for achieving the“Double Carbon”aim in the building industry are sought through this effort.
基金Humanities and Social Science Fund of Ministry of Education of China(22YJC790008)Soft Science Research Project of Xi’an Municipal Science and Technology Bureau(22RKYJ0023)Shaanxi Province Social Science Federation Fund(2022HZ1824)。
文摘Cities generate more than 60%of carbon emissions and are the main battleground for achieving the target.However,there is no unified and standardized measurement methods of carbon emissions in cities.In this paper,we took Xi’an as an example and started by measuring carbon emissions with the new standards.Then,the decoupling of economic development from carbon emissions was studied according to the Tapio decoupling theory.Based on the generalized Divisia index method,the decoupling effort model was proposed to study the impact of carbon emission factors contributing to carbon reduction.The results show:(i)During the period 1995–2021,the carbon emissions of Xi’an increased rapidly,with an average annual growth rate of 6.06%,due to the accelerating pace of urbanization and industrialization.(ii)The energy consumption sector accounted for the largest share of carbon emissions,ranging from 77.38%to 89.46%.Xi’an’s energy structure is primarily based on fossil fuels,especially coal,which holds a significant proportion.To achieve the“double carbon”goal,it is crucial to reduce the dependence on fossil fuels.(iii)The 10th Five-Year Plan was in the state of“expansive coupling”,while other periods were in the“weak decoupling”state from the 9th to 14th Five-Year Plan periods.After the carbon peak year in the 15th Five-Year Plan,it would be in a state of“strong decoupling”.The agricultural production account was the first to achieve a“strong decoupling”state.(iv)The government of Xi’an made efforts to decouple,but these were not enough.Technological innovation played a crucial role in the carbon reduction of Xi’an,and was a key factor in achieving the“double carbon”goal.
基金supported by 985 Program of Zhejiang University under Grant No.188020+193432602/215National Natural Science Foundation of China (Grant No.41175047)+3 种基金the R&D Special Fund for Public Welfare Industry by the Ministry of Finance and the Ministry of Science and Technology (Grant Nos.GYHY201006014 and 20100503310)the Basic Research Project of the State Key Laboratory of Severe Weather (12011LAS-B14)supported by the National Key Basic Research and Development Project of China under Grant Nos.2013CB430103 and 2011CB403405the National Natural Science Foundation of China under Grant Nos.41375058 and 41175065
文摘ABSTRACT Rainfall responses to doubled atmospheric carbon dioxide concentration were investigated through the analysis of two pairs of two-dimensional cloud-resolving model sensitivity experiments. One pair of experiments simulated pre-summer heavy rainfall over southern China around the summer solstice, whereas the other pair of experiments simulated tropical rainfall around the winter solstice. The analysis of the time and model domain mean heat budget revealed that the enhanced local atmospheric warming was associated with doubled carbon dioxide through the weakened infrared radiative cooling during the summer solstice. The weakened mean pre-summer rainfall corresponded to the weakened mean infrared radiative cooling. Doubled carbon dioxide increased the mean tropical atmospheric warming via the enhanced mean latent heat in correspondence with the strengthened mean infrared radiative cooling during the winter solstice. The enhanced mean tropical rainfall was associated with the increased mean latent heat.
基金the National Natural Science Foundation of China(No.21703191)Key Project of Strategic New Industry of Hunan Province(No.2016GK4005 and No.2016GK4030)Research Innovation Project for Graduate students of Hunan Province(No.CX2017B302)。
文摘Among the many strategies to fabricate the silicon/carbon composite,yolk/double-shells structure can be regarded as an effective strategy to overcome the intrinsic defects of Si-based anode materials for Li-ion batteries(LIBs).Hereon,a facile and inexpensive technology to prepare silicon/carbon composite with yolk/double-shells structure is proposed,in which the double buffering carbon shells are fabricated.The silicon/carbon nanoparticles with core-shell structure are encapsulated by SiO_(2)and external carbon layer,and it shows the yolk/double-shells structure via etching the SiO_(2)sacrificial layer.The multiply shells structure not only significantly improves the electrical conductivity of composite,but also effectively prevents the exposure of Si particles from the electrolyte composition.Meanwhile,the yolk/double-shells structure can provide enough space to accommodate the volume change of the electrode during charge/discharge process and avoid the pulverization of Si particles.Moreover,the as-prepared YDS-Si/C shows excellent performance as anode of LIBs,the reversible capacity is as high as 1066 mA h g^(-1) at the current density of 0.5 A g^(-1) after 200 cycles.At the same time,the YDS-Si/C has high capacity retention and good cyclic stability.Therefore,the unique architecture design of yolk/double-shells for Si/C composite provides an instructive exploration for the development of next generation anode materials of LIBs with high electrochemical performances and structural stability.
基金financial support from the National Natural Science Foundation of China (51274015)National Program on Key Basic Research Project (973 Program) (2014CB846000)Test Fund of Peking University
文摘1 Introduction In recent years porous carbons have been widely used in many fields such as energy storage(Mc Creery,2008;Liu et al,2009;Ho et al,2014;Yang et al,2015),adsorption,wastewater treatment,air purification
基金Sponsored by General Project of Natural Science Foundation of Beijing (8202017)Youth Talent Support Program of 2018 Beijing Municipal University Academic Human Resources Development (PXM2018_014212_000043)。
文摘Realizing “carbon peaking” and “carbon neutrality” is a major strategic decision made by China to coordinate domestic and international situations.In order to achieve the “double carbon” goal,it is also necessary for relevant practitioners to actively put into practice to improve the participation of residents and advocate low carbon life while formulating the policy action plan.Community is an important place for human activities and one of the main spatial types of carbon emissions in cities.Doing a good job in planning energy conservation and emission reduction in the community plays an important role in achieving the “double carbon” goal.Through the analysis of classic low carbon community practice cases at home and abroad,6 planning and design methods for low carbon community are concluded,and the development status of low carbon community in China is reflected and summarized.
基金financially supported by the National Natural Science Foundation of China(No.51472110)Shandong Provincial Natural Science Foundation(No.ZR2016EMB05)+1 种基金University of Jinan Science Foundation(No.XKY1630)a Research Project from Ministry of Education,China(No.213021A)
文摘The double-activated porous carbons(DAPCs)with unique bimodal pore structure were prepared by activating commercial microporous carbon(CMCs) twice through KOH(double activation) at high temperature. The as-prepared DAPCs show larger surface area(833 m^2·g^-1),and the pores are composed of micropores(size of-1.8 nm) and mesopores(size of -4.5 nm). Such special hierarchical porous structures integrate the dual advantages of micropore and mesopore, having not only the high energy storage of the micropores but also the high-rate performance of the mesopores for supercapacitors(SCs).As a result, the optimized DAPCs-3-1 exhibits a high specific capacitance of 277 F·g^-1 at 1 A·g^-1, enhanced rate performance of 197 F·g^-1 at a high current density of 10 A·g^-1, and excellent cycling stability with 94.2% capacity retention after 10,000 cycles in the 1 mol·L^-1 Na2SO4 electrolyte. The facile double activation could be a promising method to prepare suitable porous carbons with exceptional electrochemical properties for SCs.
基金financially supported by the National Natural Science Foundation of China(No.21376276)the Specialfunded Program on National Key Scientific Instruments and Equipment Development of China(No.2012YQ230043)+1 种基金Guangdong Province Sci&Tech Bureau(Key Strategic Project No.2008A080800024)the Fundamental Research Funds for the Central Universities
文摘Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides(LDHs) were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH(OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction(XRD) and scanning electron microscopy(SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient(OP) and water vapor permeability coefficient(WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.
基金Supported by the National Natural Science Foundation of China(41475039)National Key Basic Research and Development (973) Program of China(2015CB953601)
文摘The effects of doubled carbon dioxide on rainfall responses to radiative processes of water clouds are investigated in this study.Two groups of two-dimensional cloud-resolving model sensitivity experiments with regard to pre-summer heavy rainfall around the summer solstice and tropical rainfall around the winter solstice are conducted and their five-day averages over the model domain are analyzed.In the presence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the decrease associated with the enhanced atmospheric cooling to the increase associated with the enhanced infrared cooling as a result of the exclusion of radiative effects of water clouds.Doubled carbon dioxide leads to the reduction in tropical rainfall,caused by the removal of radiative effects of water clouds through the suppressed infrared cooling.In the absence of radiative effects of ice clouds,doubled carbon dioxide changes pre-summer rainfall from the increase associated with the strengthened atmospheric warming to the decrease associated with the weakened release of latent heat caused by the elimination of radiative effects of water clouds.The exclusion of radiative effects of water clouds increases tropical rainfall through the strengthened infrared cooling,which is insensitive to the change in carbon dioxide.
基金This work was supported by Jiangsu Government Scholarship for overseas studies, National Nature Science Foundation of China (Nos. 11204266 and 21276220), and Nature Science Foundation of Jiangsu Province (Nos. BK20141262 and BK20140463). The authors thank Dr. Tom Yuzvinsky from University of California, Santa Cruz for SEM images acquisition and acknowledge the W. M. Keck Center for Nanoscale Opto-fluidics for use of the FEI Quanta 3D Dual-beam scanning electron microscope. The authors also acknowledge Prof. Zhonghua Zhang from Shandong University for his help with BET characterization, Prof. Jin Z. Zhang from University of California, Santa Cruz, for offering the access to Reinshaw Raman spectrometer, Mr. Fuxin Wang from Sun Yat-sen University for TEM characterization, Prof. Xiaoxia Liu and Mr. Yu Song from Northeastern University for their generous help with AFM characterization.
文摘The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehyde- cross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer-Emmett-Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.
文摘Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe2/rGO composite with both high porosity and large surface area. Double modification of MoSe2 nanosheets is realized in this composite by introducing a reduced graphene oxide (rGO) skeleton and outer carbon protective layer. The MoSe2 nanosheets are well wrapped by a carbon layer and also strongly anchored on the interconnected rGO network. As an anode in sodium ion batteries, the designed C-MoSe2/rGO composite delivers noticeably enhanced sodium ion storage, with a high specific capacity of 445 mAh-g-1 at 200 mA.g-1 after 350 cycles, and 228 mAh-g 1 even at 4 A.g-1; these values are much better than those of C-MoSe2 nanosheets (258 mAh.g-a at 200 mA-g-1 and 75 mAh-g-1 at 4 A.g-~). Additionally, the sodium ion storage mechanism is investigated well using ex situ X-ray diffraction and transmission electron microscopy methods. Our proposed electrode design protocol and sodium storage mechanism may pave the way for the fabrication of other high-performance metal diselenide anodes for electrochemical energy storage.
文摘Polymeric nanoparticles(NPs)have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly(divinyl benzene-co-maleic anhydride)NPs(PDVBMAH NPs)through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.