Aqueous rechargeable Zn/MnO2 zinc-ion batteries(ZIBs)are reviving recently due to their low cost,non-toxicity,and natural abundance.However,their energy storage mechanism remains controversial due to their complicated...Aqueous rechargeable Zn/MnO2 zinc-ion batteries(ZIBs)are reviving recently due to their low cost,non-toxicity,and natural abundance.However,their energy storage mechanism remains controversial due to their complicated electrochemical reactions.Meanwhile,to achieve satisfactory cyclic stability and rate performance of the Zn/MnO2 ZIBs,Mn2+ is introduced in the electrolyte(e.g.,ZnSO4 solution),which leads to more complicated reactions inside the ZIBs systems.Herein,based on comprehensive analysis methods including electrochemical analysis and Pourbaix diagram,we provide novel insights into the energy storage mechanism of Zn/MnO2 batteries in the presence of Mn2+.A complex series of electrochemical reactions with the coparticipation of Zn2+,H+,Mn2+,SO42-,and OH-were revealed.During the first discharge process,co-insertion of Zn2+ and H+ promotes the transformation of MnO2 into ZnxMnO4,MnOOH,and Mn2O3,accompanying with increased electrolyte pH and the formation of ZnSO4·3 Zn(OH)2-5 H2O.During the subsequent charge process,ZnxMnO4,MnOOH,and Mn2O3 revert to a-MnO2 with the extraction of Zn2+ and H+,while ZnSO4·3Zn(OH)2·5H2O reacts with Mn2+ to form ZnMn3O7·3 H2O.In the following charge/discharge processes,besides aforementioned electrochemical reactions,Zn2+ reversibly insert into/extract from α-MnO2,ZnxMnO4,and ZnMn3O7·3H2O hosts;ZnSO4·3Zn(OH)2·5 H2O,Zn2Mn3O8,and ZnMn2O4 convert mutually with the participation of Mn2+.This work is believed to provide theoretical guidance for further research on high-performance ZIBs.展开更多
Rechargeable aqueous zinc-ion batteries(ZIB s) have been gaining increasing interest for large-scale energy storage applications due to their high safety,good rate capability,and low cost.However,the further developme...Rechargeable aqueous zinc-ion batteries(ZIB s) have been gaining increasing interest for large-scale energy storage applications due to their high safety,good rate capability,and low cost.However,the further development of ZIB s is impeded by two main challenges:Currently reported cathode materials usually suffer from rapid capacity fading or high toxicity,and meanwhile,unstable zinc stripping/plating on Zn anode seriously shortens the cycling life of ZIBs.In this paper,metal-organic framework(MOF) materials are proposed to simultaneously address these issues and realize high-performance ZIB s with Mn(BTC) MOF cathodes and ZIF-8-coated Zn(ZIF-8@Zn) anodes.Various MOF materials were synthesized,and Mn(BTC) MOF was found to exhibit the best Zn^2+-storage ability with a capacity of 112 mAh g^-1.Zn^2+ storage mechanism of the Mn(BTC) was carefully studied.Besides,ZIF-8@Zn anodes were prepared by coating ZIF-8 MOF material on Zn foils.Unique porous structure of the ZIF-8 coating guided uniform Zn stripping/plating on the surface of Zn anodes.As a result,the ZIF-8@Zn anodes exhibited stable Zn stripping/plating behaviors,with 8 times longer cycle life than bare Zn foils.Based on the above,high-performance aqueous ZIBs were constructed using the Mn(BTC) cathodes and the ZIF-8@Zn anodes,which displayed an excellent long-cycling stability without obvious capacity fading after 900 charge/discharge cycles.This work provides a new opportunity for high-performance energy storage system.展开更多
Few-layer Ti3C2Tx MXene is synthesized from multi-layered Ti3C2Tx via a flash freezing-assisted delamination process.During the flash freezing process,the water molecules in the interlayers of multi-layered MXene are ...Few-layer Ti3C2Tx MXene is synthesized from multi-layered Ti3C2Tx via a flash freezing-assisted delamination process.During the flash freezing process,the water molecules in the interlayers of multi-layered MXene are induced to rearrange and produce volume expansion,thus notably expand the MXenes’interlayer distance to form few-layer MXene.The synthesized few-layer Ti3C2Tx MXene nanosheets display a very small thickness(less than 5 Ti3C2 atom-layers)and expanded interlayer spacing.Consequently,the few-layer Ti3C2Tx exhibits enhanced capacitance(255 F g^-1 vs.177 F g^-1 for the multi-layered Ti3C2Tx)and significantly optimized rate capability(150 F g^-1 at 200 mV s^-1 vs.25 F g^-1 for the multi-layered Ti3C2Tx),because redox-active sites in the few-layer MXene are easily accessible to electrolyte ions.Moreover,an asymmetric supercapacitor is constructed using the few-layer Ti3C2Tx negative electrode and an activated carbon fiber positive electrode.The asymmetric supercapacitor presents a high energy density of 17.9 Wh kg^-1 and a high power density of 14 kW kg^-1,which is inseparable from its wide voltage window of 1.4 V and the good rate performance of the few-layer Ti3C2Tx MXene electrode.Overall,the flash freezing-assist delamination provides an effective and environmental-friendly strategy to synthesize few-layer MXene materials for high-rate electrochemical energy storage.展开更多
The "Old Red Sand" is widely distributed along the coast of Fujian Province, China. Most studies have been carried out from as- pects of the origin, age and laterization of the "Old Red Sand", but this paper focus...The "Old Red Sand" is widely distributed along the coast of Fujian Province, China. Most studies have been carried out from as- pects of the origin, age and laterization of the "Old Red Sand", but this paper focused on reconstructing the history of the Asian Winter Monsoon change. On the basis of granulometric analysis of high-resohition samples, we have obtained environmental sen- sitive grain size component (ESGSC) from the Qingfeng (QF) profile by using the grain size-standard deviation method, which proves that the selected ESGSC is an important climate proxy. The mean grain size of this ESGSC could be used to reconstruct the East Asian Winter Monsoon (EAWM) intensity. As such, the history of the EAWM change since 44.0 ka reconstructed here reveals three main phases based on chronology dates of previous researches: (1) 44.0-25.5 ka B.P., the EAWM is relatively weak but increases gradually with fluctuations; (2) 25.5-15.5 ka B.P., relatively strong with high frequency fluctuations; (3) 15.5-7.1 ka B.P., with a weaker winter monsoon, but during 11-10 ka B.P. is remarkably enhanced. The EAWM recorded by mean grain size of the two neighboring sections have a better repeatability, so the millennial scales oscillation should be a reliable signal of the EAWM intensity. The climate recorded by ESGSC of the QF "Old Red Sand" compared to 6-80 of Huhi Cave stalagmites and Greenland GISP2 ice cores shows a good consistency, especially in detail, the YD event and four Heinrich events are all recorded, but the signal of D-O cycles was relatively weak.展开更多
Introduction:The Canadian Forest Fire Danger Rating System(CFFDRS)is a globally known wildland fire risk assessment system,and two major components,the fire weather index system and the fire behavior prediction system...Introduction:The Canadian Forest Fire Danger Rating System(CFFDRS)is a globally known wildland fire risk assessment system,and two major components,the fire weather index system and the fire behavior prediction system,have been extensively used both nationally and internationally to aid operational wildland fire decision making.Methods:In this paper,we present an overview of an R package cffdrs,which is developed to calculate components of the CFFDRS,and highlight some of its functionality.In particular,we demonstrate how these functions could be used for large data analysis.Results and Discussion:With this cffdrs package,we provide a portal for not only a collection of R functions dealing with all available components in CFFDRS but also a platform for various additional developments that are useful for the understanding of fire occurrence and behavior.This is the first time that all relevant CFFDRS methods are incorporated into the same platform,which can be accessed by both the management and research communities.展开更多
With an upsurge of biodegradable metal implants,the research and application of Mg alloys in the gastrointestinal environment of the digestive tract have been of great interest.Digestive enzymes,mainly pepsin in the s...With an upsurge of biodegradable metal implants,the research and application of Mg alloys in the gastrointestinal environment of the digestive tract have been of great interest.Digestive enzymes,mainly pepsin in the stomach and pancreatin in the small intestine,are widespread in the gastrointestinal tract,but their effect on the degradation of Mg alloys has not been well understood.In this study,we investigated the impacts of pepsin and pancreatin on the degradation of Mg-2Zn alloy wires.The results showed that the pepsin and pancreatin had completely different even the opposite effects on the degradation of Mg,although they both affected the degradation product layer.The degradation rate of Mg wire declined with the addition of pepsin in simulated gastric fluid(SGF)but rose with the addition of pancreatin in simulated intestinal fluid(SIF).The opposite trends in degradation rate also resulted in completely different degradation morphologies in wires surface,where the pitting corrosion in SGF was inhibited because of the physical barrier effect of pepsin adsorption.In contrast,the adsorption of pancreatin affected the integrity of magnesium hydrogen phosphate film,causing a relatively uneven degraded surface.These results may help us to understand the role of different digestive enzymes in the degradation of magnesium and facilitate the development and clinical application of magnesium alloy implanted devices for the digestive tract.展开更多
Correction The original publication(cffdrs,2017)has an error in the citation of figure 1.Below you will find the correct version.Incorrect version:The Canadian Forest Fire Danger Rating System flow chart(FCFDG 1992)Co...Correction The original publication(cffdrs,2017)has an error in the citation of figure 1.Below you will find the correct version.Incorrect version:The Canadian Forest Fire Danger Rating System flow chart(FCFDG 1992)Correct version:The Canadian Forest Fire Danger Rating System flow chart(Stocks et al.1989).展开更多
基金the financial support from the International Science & Technology Cooperation Program of China (No. 2016YFE0102200)Shenzhen Technical Plan Project (No. JCYJ20160301154114273)+1 种基金National Key Basic Research(973) Program of China (No. 2014CB932400)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01N111)
文摘Aqueous rechargeable Zn/MnO2 zinc-ion batteries(ZIBs)are reviving recently due to their low cost,non-toxicity,and natural abundance.However,their energy storage mechanism remains controversial due to their complicated electrochemical reactions.Meanwhile,to achieve satisfactory cyclic stability and rate performance of the Zn/MnO2 ZIBs,Mn2+ is introduced in the electrolyte(e.g.,ZnSO4 solution),which leads to more complicated reactions inside the ZIBs systems.Herein,based on comprehensive analysis methods including electrochemical analysis and Pourbaix diagram,we provide novel insights into the energy storage mechanism of Zn/MnO2 batteries in the presence of Mn2+.A complex series of electrochemical reactions with the coparticipation of Zn2+,H+,Mn2+,SO42-,and OH-were revealed.During the first discharge process,co-insertion of Zn2+ and H+ promotes the transformation of MnO2 into ZnxMnO4,MnOOH,and Mn2O3,accompanying with increased electrolyte pH and the formation of ZnSO4·3 Zn(OH)2-5 H2O.During the subsequent charge process,ZnxMnO4,MnOOH,and Mn2O3 revert to a-MnO2 with the extraction of Zn2+ and H+,while ZnSO4·3Zn(OH)2·5H2O reacts with Mn2+ to form ZnMn3O7·3 H2O.In the following charge/discharge processes,besides aforementioned electrochemical reactions,Zn2+ reversibly insert into/extract from α-MnO2,ZnxMnO4,and ZnMn3O7·3H2O hosts;ZnSO4·3Zn(OH)2·5 H2O,Zn2Mn3O8,and ZnMn2O4 convert mutually with the participation of Mn2+.This work is believed to provide theoretical guidance for further research on high-performance ZIBs.
基金the financial supports from International Science & Technology Cooperation Program of China (No. 2016YFE0102200)Shenzhen Technical Plan Project (No. JCYJ20160301154114273)+1 种基金National Key Basic Research (973) Program of China (No. 2014CB932400)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01N111)。
文摘Rechargeable aqueous zinc-ion batteries(ZIB s) have been gaining increasing interest for large-scale energy storage applications due to their high safety,good rate capability,and low cost.However,the further development of ZIB s is impeded by two main challenges:Currently reported cathode materials usually suffer from rapid capacity fading or high toxicity,and meanwhile,unstable zinc stripping/plating on Zn anode seriously shortens the cycling life of ZIBs.In this paper,metal-organic framework(MOF) materials are proposed to simultaneously address these issues and realize high-performance ZIB s with Mn(BTC) MOF cathodes and ZIF-8-coated Zn(ZIF-8@Zn) anodes.Various MOF materials were synthesized,and Mn(BTC) MOF was found to exhibit the best Zn^2+-storage ability with a capacity of 112 mAh g^-1.Zn^2+ storage mechanism of the Mn(BTC) was carefully studied.Besides,ZIF-8@Zn anodes were prepared by coating ZIF-8 MOF material on Zn foils.Unique porous structure of the ZIF-8 coating guided uniform Zn stripping/plating on the surface of Zn anodes.As a result,the ZIF-8@Zn anodes exhibited stable Zn stripping/plating behaviors,with 8 times longer cycle life than bare Zn foils.Based on the above,high-performance aqueous ZIBs were constructed using the Mn(BTC) cathodes and the ZIF-8@Zn anodes,which displayed an excellent long-cycling stability without obvious capacity fading after 900 charge/discharge cycles.This work provides a new opportunity for high-performance energy storage system.
基金financial supports from Shenzhen Technical Plan Project(No.JCYJ20160301154114273No.JCYJ20170412171430026)+2 种基金International Science and Technology Cooperation Program of China(No.2016YFE0102200)National Key Basic Research(973)Program of China(No.2014CB932400)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01N111)。
文摘Few-layer Ti3C2Tx MXene is synthesized from multi-layered Ti3C2Tx via a flash freezing-assisted delamination process.During the flash freezing process,the water molecules in the interlayers of multi-layered MXene are induced to rearrange and produce volume expansion,thus notably expand the MXenes’interlayer distance to form few-layer MXene.The synthesized few-layer Ti3C2Tx MXene nanosheets display a very small thickness(less than 5 Ti3C2 atom-layers)and expanded interlayer spacing.Consequently,the few-layer Ti3C2Tx exhibits enhanced capacitance(255 F g^-1 vs.177 F g^-1 for the multi-layered Ti3C2Tx)and significantly optimized rate capability(150 F g^-1 at 200 mV s^-1 vs.25 F g^-1 for the multi-layered Ti3C2Tx),because redox-active sites in the few-layer MXene are easily accessible to electrolyte ions.Moreover,an asymmetric supercapacitor is constructed using the few-layer Ti3C2Tx negative electrode and an activated carbon fiber positive electrode.The asymmetric supercapacitor presents a high energy density of 17.9 Wh kg^-1 and a high power density of 14 kW kg^-1,which is inseparable from its wide voltage window of 1.4 V and the good rate performance of the few-layer Ti3C2Tx MXene electrode.Overall,the flash freezing-assist delamination provides an effective and environmental-friendly strategy to synthesize few-layer MXene materials for high-rate electrochemical energy storage.
基金supported by the National Natural Science Foundation of China(Grant No.41271031)the Open Foundation of State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,CAS(Grant No.SKLLQG1113)
文摘The "Old Red Sand" is widely distributed along the coast of Fujian Province, China. Most studies have been carried out from as- pects of the origin, age and laterization of the "Old Red Sand", but this paper focused on reconstructing the history of the Asian Winter Monsoon change. On the basis of granulometric analysis of high-resohition samples, we have obtained environmental sen- sitive grain size component (ESGSC) from the Qingfeng (QF) profile by using the grain size-standard deviation method, which proves that the selected ESGSC is an important climate proxy. The mean grain size of this ESGSC could be used to reconstruct the East Asian Winter Monsoon (EAWM) intensity. As such, the history of the EAWM change since 44.0 ka reconstructed here reveals three main phases based on chronology dates of previous researches: (1) 44.0-25.5 ka B.P., the EAWM is relatively weak but increases gradually with fluctuations; (2) 25.5-15.5 ka B.P., relatively strong with high frequency fluctuations; (3) 15.5-7.1 ka B.P., with a weaker winter monsoon, but during 11-10 ka B.P. is remarkably enhanced. The EAWM recorded by mean grain size of the two neighboring sections have a better repeatability, so the millennial scales oscillation should be a reliable signal of the EAWM intensity. The climate recorded by ESGSC of the QF "Old Red Sand" compared to 6-80 of Huhi Cave stalagmites and Greenland GISP2 ice cores shows a good consistency, especially in detail, the YD event and four Heinrich events are all recorded, but the signal of D-O cycles was relatively weak.
文摘Introduction:The Canadian Forest Fire Danger Rating System(CFFDRS)is a globally known wildland fire risk assessment system,and two major components,the fire weather index system and the fire behavior prediction system,have been extensively used both nationally and internationally to aid operational wildland fire decision making.Methods:In this paper,we present an overview of an R package cffdrs,which is developed to calculate components of the CFFDRS,and highlight some of its functionality.In particular,we demonstrate how these functions could be used for large data analysis.Results and Discussion:With this cffdrs package,we provide a portal for not only a collection of R functions dealing with all available components in CFFDRS but also a platform for various additional developments that are useful for the understanding of fire occurrence and behavior.This is the first time that all relevant CFFDRS methods are incorporated into the same platform,which can be accessed by both the management and research communities.
基金This work was supported by the National Key Research and Development Program of China(2016YFC1102402)the National Natural Science Foundation of China(51971062)+2 种基金the Science and Technology Project of Jiangsu Province(BE2019679)the Technological Innovation of key Industry of Suzhou(SYG201904)and the open research fund of Jiangsu Key Laboratory for Advanced Metallic Materials(AMM2021A01).
文摘With an upsurge of biodegradable metal implants,the research and application of Mg alloys in the gastrointestinal environment of the digestive tract have been of great interest.Digestive enzymes,mainly pepsin in the stomach and pancreatin in the small intestine,are widespread in the gastrointestinal tract,but their effect on the degradation of Mg alloys has not been well understood.In this study,we investigated the impacts of pepsin and pancreatin on the degradation of Mg-2Zn alloy wires.The results showed that the pepsin and pancreatin had completely different even the opposite effects on the degradation of Mg,although they both affected the degradation product layer.The degradation rate of Mg wire declined with the addition of pepsin in simulated gastric fluid(SGF)but rose with the addition of pancreatin in simulated intestinal fluid(SIF).The opposite trends in degradation rate also resulted in completely different degradation morphologies in wires surface,where the pitting corrosion in SGF was inhibited because of the physical barrier effect of pepsin adsorption.In contrast,the adsorption of pancreatin affected the integrity of magnesium hydrogen phosphate film,causing a relatively uneven degraded surface.These results may help us to understand the role of different digestive enzymes in the degradation of magnesium and facilitate the development and clinical application of magnesium alloy implanted devices for the digestive tract.
文摘Correction The original publication(cffdrs,2017)has an error in the citation of figure 1.Below you will find the correct version.Incorrect version:The Canadian Forest Fire Danger Rating System flow chart(FCFDG 1992)Correct version:The Canadian Forest Fire Danger Rating System flow chart(Stocks et al.1989).