Polymeric organic battery materials are promising alternatives to the transition-metal-based ones owing to their enriched chemistries. However, the flammability of organic compounds brings in serious concern on batter...Polymeric organic battery materials are promising alternatives to the transition-metal-based ones owing to their enriched chemistries. However, the flammability of organic compounds brings in serious concern on battery safety. In addition to use flame-retarding electrolyte/electrolyte additives or battery separators,flame retardancy can readily be achieved through the integration of flame-retarding unit into the polymer backbone, imparting the flame retardancy permanently. The as-designed polymer based on phenothiazine shows significantly shortened self-extinguished time without deteriorating its intrinsic thermodynamic and electrochemical properties. Moreover, two electron per phenothiazine molecule is realized for the first time in a highly reversible manner with discharge voltages of 3.52 V and 4.16 V versus Li+/Li and an average capacity of ca. 120 mAh g-1 at a current rate of 2 C. The origin of the reversibility is investigated through density functional theory(DFT) calculations. These findings address the importance of molecular design for safer and more stable organic materials for batteries.展开更多
High-performance lithium ion batteries(LIBs) require electrode material to have an ideal electrode construction which provides fast ion transport, short solid-state ion diffusion, large surface area, and high electric...High-performance lithium ion batteries(LIBs) require electrode material to have an ideal electrode construction which provides fast ion transport, short solid-state ion diffusion, large surface area, and high electric conductivity. Herein, highly porous three-dimensional(3D)aerogels composed of cobalt ferrite(CoFe_2O_4, CFO) nanoparticles(NPs) and carbon nanotubes(CNTs) are prepared using sustainable alginate as the precursor. The key feature of this work is that by using the characteristic egg-box structure of the alginate, metal cations such as Co^(2+)and Fe^(3+) can be easily chelated via an ion-exchange process, thus binary CFO are expected to be prepared. In the hybrid aerogels, CFO NPs interconnected by the CNTs are embedded in carbon aerogel matrix, forming the 3D network which can provide high surface area, buffer the volume expansion and offer efficient ion and electron transport pathways for achieving high performance LIBs. The as-prepared hybrid aerogels with the optimum CNT content(20 wt%) delivers excellent electrochemical properties, i.e., reversible capacity of 1033 mAh g^(-1) at 0.1 A g^(-1) and a high specific capacity of 874 mAh g^(-1) after 160 cycles at 1 A g^(-1). This work provides a facile and low cost route to fabricate high performance anodes for LIBs.展开更多
Alloyed based anode materials with high theoretical specific capacity and low reaction potential are considered to be highly potential high-energy density anode materials for alkali metal ion batteries(AMIBs).Thus,the...Alloyed based anode materials with high theoretical specific capacity and low reaction potential are considered to be highly potential high-energy density anode materials for alkali metal ion batteries(AMIBs).Thus,the design of alloyed based materials with high electrochemical performance has attracted great attention.Among the numerous characterization methods for guiding electrode materials design,in situ transmission electron microscopy(TEM)gradually plays an irreplaceable role due to its high temporal and spatial resolution in directly observing the change of morphology,crystal structure and element evolutions.Herein,we reviewed the two current research hotspots and mainly focused on the structure design of alloyed based electrode material under the guidance of in situ TEM.Specifically,various nanostructure designs of alloyed based electrode materials with guidance of in situ TEM were employed to solve the key scientific issues of the violent volume change during alloying/dealloying processes for enhanced electrochemical performances.Mainly through introducing buffer space in the electrode material to reduce volume change to improve structural stability,including porous structure(0 D),nanotube structure(1 D),simple hollow structure,yolk-shell structure and some hybrid hollow structures(3 D).Furthermore,the direct guidance of in situ TEM is expected for creating new opportunities to nextgeneration electrode material design for AMIBs.展开更多
To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlatio...To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlation between stable isotope ratio and trophic level were established to predict the trophic levels of shrimps,crabs,cephalopods and fishes.By comparing the analysis results of stomach contents of 24 organisms,two methods gave a similar consistence in approximately 71% of organisms within a 0.5 trophic level.It is concluded that stable isotope technique could be an effective method for studying ocean food web trophic level.展开更多
The preparation of supported high-density metal nanoparticles(NPs)is of great importance to boost the performance in heterogeneous catalysis.Thermal transformation of metal-organic frameworks(MOFs)has been demonstrate...The preparation of supported high-density metal nanoparticles(NPs)is of great importance to boost the performance in heterogeneous catalysis.Thermal transformation of metal-organic frameworks(MOFs)has been demonstrated as a promising route for the synthesis of supported metal NPs with high metal loadings,but it is challenge to achieve uniform metal dispersion.Here we report a strategy of“spatial isolation and dopant anchoring”to resist metal aggregation in the pyrolysis of MOFs through converting a bulk MOF into dual-heteroatom-containing flower-like MOF sheets(B/N-MOF-S).This approach can spatially isolate metal ions and increase the number of anchoring sites,thus efficiently building physical and/or chemical barriers to cooperatively prevent metal NPs from aggregation in the high-temperature transformation process.After thermolysis at 1,000℃,the B/N-MOFS affords B,N co-doped carbon-supported Co NPs(Co/BNC)with uniform dispersion and a high Co loading of 37.3 wt.%,while untreated bulk MOFs yield much larger sizes and uneven distribution of Co NPs.The as-obtained Co/BNC exhibits excellent electrocatalytic activities in both hydrogen evolution and hydrazine oxidation reactions,only a voltage of 0.617 V at a high current density of 100 mA·cm^(−2)is required when applied to a two-electrode overall hydrazine splitting electrolyzer.展开更多
In the carbon dioxide reduction reaction(CO_(2)RR),the activity of transition metal center depends largely on its electronic structure,since the electronic rich region enhances the adsorption of intermediates at activ...In the carbon dioxide reduction reaction(CO_(2)RR),the activity of transition metal center depends largely on its electronic structure,since the electronic rich region enhances the adsorption of intermediates at active sites,thus improving the selectivity to reduction products.In this work,we prepared CuPc/DG composite(CuPc:copper phthalocyanine;DG:defective graphene)to achieve selective CO_(2)-to-formic acid(HCOOH)electrochemical conversion through modulating the electronic structure of Cu active centers with DG via π-π stacking.Evaluated as the electrocatalyst,the CuPc/DG composite displays a high faradaic efficiency(FE)of 44.6%−0.78 V vs.RHE for CO_(2)RR to HCOOH.Partial current density is 5.28 mA cm^(−2) for HCOOH together with an exceptional stability throughout at least 20 h of reaction.On the basis of density functional theory(DFT)calculation results,defects in DG can effectively promote the charge redistribution of dispersed CuPc,where electrons transfer to CuPc from defects,forming rich electronic environment around Cu sites.The abundance of electrons makes the d-band center of Cu approach to the Fermi level and decrease the energy barrier of CuPc/DG composite for the intermediate of ∗OCHO,thus accelerating the reduction of CO_(2) to HCOOH.展开更多
Silicon is attracting considerable attention as an active anode material for advanced lithium-ion batteries due to its ultrahigh theoretical capacity. However, the reversible utilization of silicon-based anode materia...Silicon is attracting considerable attention as an active anode material for advanced lithium-ion batteries due to its ultrahigh theoretical capacity. However, the reversible utilization of silicon-based anode materials is still hindered by the rapid capacity decay, as a consequence of the huge volume change of silicon during cycling. Herein, we use a Co-zeolitic imidazole framework(ZIF-67) to prepare silicon-wrapped nitrogen-doped carbon nanotubes(Si@N-doped CNTs) by controllable thermal pyrolysis. The asprepared nanocomposites can effectively prevent pulverization and accommodate volume fluctuations of silicon during cycling. It can deliver a highly reversible capacity of 1100 m Ah g-1 even after 750 cycles at a current density of 1000 m A g-1. As confirmed by an in situ transmission electron microscopy experiment, the remarkable electrochemical performance of Si@N-doped CNTs is attributed to the high electronic conductivity and flexibility of cross-linked N-doped CNTs network as a cushion to mitigate the mechanical stress and volume expansion. Furthermore, a full cell consisting of Si@N-doped CNTs anode and Li Fe PO4 cathode delivers a high reversible capacity of 1264 m Ah g-1 and exhibits good cycling stability(>85% capacity retention) over 140 cycles at 1/4 C(1 C = 4000 m A g-1) rate.展开更多
Fossil plants play an important role in geoscience, such as in the determination of strata and analysis of evolution of natural environment. The vestiges of plant leaves embedded in rocks are usually blurred. This mak...Fossil plants play an important role in geoscience, such as in the determination of strata and analysis of evolution of natural environment. The vestiges of plant leaves embedded in rocks are usually blurred. This makes manual analysis difficult. The computer image processing and analysis has the following advantages: (i)enhancing useful information of展开更多
Highly-open nanoframe structures consisting of interconnected and exposed ridges are highly desirable for achieving efficient catalysis,but preparing them by a facile etching-free methodology is still a very daunting ...Highly-open nanoframe structures consisting of interconnected and exposed ridges are highly desirable for achieving efficient catalysis,but preparing them by a facile etching-free methodology is still a very daunting task.Herein,we propose a novel metal-organic framework(MOF)-assisted and etching-free strategy for the construction of Co/N-doped carbon nanoframes with highly-open and precisely-controllable structures.This strategy is based on the face-selective epitaxial growth of ZIF-67 on the 36{110}facets of 72-facet ZIF-8 to form an unprecedented anisotropic ZIF-67-on-ZIF-8 heterostructure,which is subsequently pyrolyzed under Ar atmosphere to realize a solid-to-frame transformation.The highly-open nanoframe structure enables the substrates to readily penetrate into the catalyst interior and thereby create additional exposed active sites,which together with the good mass transport,high atomic utilization and increased surface area are responsible for its remarkably enhanced catalytic activity for the biomass valorisation when compared with its solid and closed hollow counterparts.This study could shed valuable insights into the design and preparation of various highly-open nanoframes with abundant exposed active species by using an etching-free strategy for efficient catalysis and beyond.展开更多
基金financial support from the National Natural Science Foundation of China (grant no.51772199)the Natural Science Foundation of Jiangsu Province (Grant no.BK20170329)+2 种基金the Collaborative Innovation Center of Suzhou Nano Science & Technologythe Priority Academic Program Development of Jiangsu Higher Education Institutionsthe 111 Project。
文摘Polymeric organic battery materials are promising alternatives to the transition-metal-based ones owing to their enriched chemistries. However, the flammability of organic compounds brings in serious concern on battery safety. In addition to use flame-retarding electrolyte/electrolyte additives or battery separators,flame retardancy can readily be achieved through the integration of flame-retarding unit into the polymer backbone, imparting the flame retardancy permanently. The as-designed polymer based on phenothiazine shows significantly shortened self-extinguished time without deteriorating its intrinsic thermodynamic and electrochemical properties. Moreover, two electron per phenothiazine molecule is realized for the first time in a highly reversible manner with discharge voltages of 3.52 V and 4.16 V versus Li+/Li and an average capacity of ca. 120 mAh g-1 at a current rate of 2 C. The origin of the reversibility is investigated through density functional theory(DFT) calculations. These findings address the importance of molecular design for safer and more stable organic materials for batteries.
基金financially supported by the National Natural Science Foundation of China (No. 51473081 and 51503109)Research award fund for outstanding young scientists in Shandong province (Grant no. BS2014CL006)Qingdao Applied Basic Research Project(16-5-1-85-jch)
文摘High-performance lithium ion batteries(LIBs) require electrode material to have an ideal electrode construction which provides fast ion transport, short solid-state ion diffusion, large surface area, and high electric conductivity. Herein, highly porous three-dimensional(3D)aerogels composed of cobalt ferrite(CoFe_2O_4, CFO) nanoparticles(NPs) and carbon nanotubes(CNTs) are prepared using sustainable alginate as the precursor. The key feature of this work is that by using the characteristic egg-box structure of the alginate, metal cations such as Co^(2+)and Fe^(3+) can be easily chelated via an ion-exchange process, thus binary CFO are expected to be prepared. In the hybrid aerogels, CFO NPs interconnected by the CNTs are embedded in carbon aerogel matrix, forming the 3D network which can provide high surface area, buffer the volume expansion and offer efficient ion and electron transport pathways for achieving high performance LIBs. The as-prepared hybrid aerogels with the optimum CNT content(20 wt%) delivers excellent electrochemical properties, i.e., reversible capacity of 1033 mAh g^(-1) at 0.1 A g^(-1) and a high specific capacity of 874 mAh g^(-1) after 160 cycles at 1 A g^(-1). This work provides a facile and low cost route to fabricate high performance anodes for LIBs.
基金supported by the National Natural Science Foundation of China(No.51621001)the National Key Research and Development Program of China(No.2016YFA0202604)Key Laboratory of Resource Chemistry,Ministry of Education Joint International Research Laboratory of Resource Chemistry and the open fund from Hunan Provincial Key Laboratory of Advanced Materials for New Energy Storage and Conversion(No.2018TP1037-202005)。
文摘Alloyed based anode materials with high theoretical specific capacity and low reaction potential are considered to be highly potential high-energy density anode materials for alkali metal ion batteries(AMIBs).Thus,the design of alloyed based materials with high electrochemical performance has attracted great attention.Among the numerous characterization methods for guiding electrode materials design,in situ transmission electron microscopy(TEM)gradually plays an irreplaceable role due to its high temporal and spatial resolution in directly observing the change of morphology,crystal structure and element evolutions.Herein,we reviewed the two current research hotspots and mainly focused on the structure design of alloyed based electrode material under the guidance of in situ TEM.Specifically,various nanostructure designs of alloyed based electrode materials with guidance of in situ TEM were employed to solve the key scientific issues of the violent volume change during alloying/dealloying processes for enhanced electrochemical performances.Mainly through introducing buffer space in the electrode material to reduce volume change to improve structural stability,including porous structure(0 D),nanotube structure(1 D),simple hollow structure,yolk-shell structure and some hybrid hollow structures(3 D).Furthermore,the direct guidance of in situ TEM is expected for creating new opportunities to nextgeneration electrode material design for AMIBs.
基金Supported by Public Science and Technology Research Funds Projects of Ocean(200905005-05)Special S&T Program for Key Independent Innovation in Guangdong Province(2007A032600004)
文摘To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlation between stable isotope ratio and trophic level were established to predict the trophic levels of shrimps,crabs,cephalopods and fishes.By comparing the analysis results of stomach contents of 24 organisms,two methods gave a similar consistence in approximately 71% of organisms within a 0.5 trophic level.It is concluded that stable isotope technique could be an effective method for studying ocean food web trophic level.
基金the National Natural Science Foundation of China(Nos.21825802,22138003,22108083,and 52172142)the Foundation of Advanced Catalytic Engineering Research Center of the Ministry of Education(No.2020AC006)+4 种基金the Science and Technology Program of Qingyuan City(No.2021YFJH01002)the Natural Science Foundation of Guangdong Province(No.2017A030312005)the Guangdong University Students Special Fund for Science and Technology Innovation Cultivation(No.pdjh2022a0031)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.202210561050)the Science and Technology Program of Guangzhou(No.202201010118).
文摘The preparation of supported high-density metal nanoparticles(NPs)is of great importance to boost the performance in heterogeneous catalysis.Thermal transformation of metal-organic frameworks(MOFs)has been demonstrated as a promising route for the synthesis of supported metal NPs with high metal loadings,but it is challenge to achieve uniform metal dispersion.Here we report a strategy of“spatial isolation and dopant anchoring”to resist metal aggregation in the pyrolysis of MOFs through converting a bulk MOF into dual-heteroatom-containing flower-like MOF sheets(B/N-MOF-S).This approach can spatially isolate metal ions and increase the number of anchoring sites,thus efficiently building physical and/or chemical barriers to cooperatively prevent metal NPs from aggregation in the high-temperature transformation process.After thermolysis at 1,000℃,the B/N-MOFS affords B,N co-doped carbon-supported Co NPs(Co/BNC)with uniform dispersion and a high Co loading of 37.3 wt.%,while untreated bulk MOFs yield much larger sizes and uneven distribution of Co NPs.The as-obtained Co/BNC exhibits excellent electrocatalytic activities in both hydrogen evolution and hydrazine oxidation reactions,only a voltage of 0.617 V at a high current density of 100 mA·cm^(−2)is required when applied to a two-electrode overall hydrazine splitting electrolyzer.
基金support by the National Natural Science Foundation of China(No.52102362)Taishan Scholar Foundation(No.ts201712030)+2 种基金Outstanding Youth of Natural Science in Shandong Province(No.JQ201713)Natural Science Foundation of Shandong Province(Nos.ZR2021QB022,ZR2021QB083,ZR2021ME012)State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University,Nos.ZKT10,ZKT25,ZKT30,and ZDKT202105).
文摘In the carbon dioxide reduction reaction(CO_(2)RR),the activity of transition metal center depends largely on its electronic structure,since the electronic rich region enhances the adsorption of intermediates at active sites,thus improving the selectivity to reduction products.In this work,we prepared CuPc/DG composite(CuPc:copper phthalocyanine;DG:defective graphene)to achieve selective CO_(2)-to-formic acid(HCOOH)electrochemical conversion through modulating the electronic structure of Cu active centers with DG via π-π stacking.Evaluated as the electrocatalyst,the CuPc/DG composite displays a high faradaic efficiency(FE)of 44.6%−0.78 V vs.RHE for CO_(2)RR to HCOOH.Partial current density is 5.28 mA cm^(−2) for HCOOH together with an exceptional stability throughout at least 20 h of reaction.On the basis of density functional theory(DFT)calculation results,defects in DG can effectively promote the charge redistribution of dispersed CuPc,where electrons transfer to CuPc from defects,forming rich electronic environment around Cu sites.The abundance of electrons makes the d-band center of Cu approach to the Fermi level and decrease the energy barrier of CuPc/DG composite for the intermediate of ∗OCHO,thus accelerating the reduction of CO_(2) to HCOOH.
基金supported by the National Key Research and Development Program of China (2018YFA0209600)the National Natural Science Foundation of China (21872058)+1 种基金the Key Project of Science and Technology in Guangdong Province (2017A010106006)the Guangdong Special Support Program (2017TQ04N052)。
文摘Silicon is attracting considerable attention as an active anode material for advanced lithium-ion batteries due to its ultrahigh theoretical capacity. However, the reversible utilization of silicon-based anode materials is still hindered by the rapid capacity decay, as a consequence of the huge volume change of silicon during cycling. Herein, we use a Co-zeolitic imidazole framework(ZIF-67) to prepare silicon-wrapped nitrogen-doped carbon nanotubes(Si@N-doped CNTs) by controllable thermal pyrolysis. The asprepared nanocomposites can effectively prevent pulverization and accommodate volume fluctuations of silicon during cycling. It can deliver a highly reversible capacity of 1100 m Ah g-1 even after 750 cycles at a current density of 1000 m A g-1. As confirmed by an in situ transmission electron microscopy experiment, the remarkable electrochemical performance of Si@N-doped CNTs is attributed to the high electronic conductivity and flexibility of cross-linked N-doped CNTs network as a cushion to mitigate the mechanical stress and volume expansion. Furthermore, a full cell consisting of Si@N-doped CNTs anode and Li Fe PO4 cathode delivers a high reversible capacity of 1264 m Ah g-1 and exhibits good cycling stability(>85% capacity retention) over 140 cycles at 1/4 C(1 C = 4000 m A g-1) rate.
文摘Fossil plants play an important role in geoscience, such as in the determination of strata and analysis of evolution of natural environment. The vestiges of plant leaves embedded in rocks are usually blurred. This makes manual analysis difficult. The computer image processing and analysis has the following advantages: (i)enhancing useful information of
基金supported by Guangdong Natural Science Funds for Distinguished Young Scholar(2018B030306050)the National Natural Science Foundation of China(22138003,21825802)the Natural Science Foundation of Guangdong Province(2017A030312005).
文摘Highly-open nanoframe structures consisting of interconnected and exposed ridges are highly desirable for achieving efficient catalysis,but preparing them by a facile etching-free methodology is still a very daunting task.Herein,we propose a novel metal-organic framework(MOF)-assisted and etching-free strategy for the construction of Co/N-doped carbon nanoframes with highly-open and precisely-controllable structures.This strategy is based on the face-selective epitaxial growth of ZIF-67 on the 36{110}facets of 72-facet ZIF-8 to form an unprecedented anisotropic ZIF-67-on-ZIF-8 heterostructure,which is subsequently pyrolyzed under Ar atmosphere to realize a solid-to-frame transformation.The highly-open nanoframe structure enables the substrates to readily penetrate into the catalyst interior and thereby create additional exposed active sites,which together with the good mass transport,high atomic utilization and increased surface area are responsible for its remarkably enhanced catalytic activity for the biomass valorisation when compared with its solid and closed hollow counterparts.This study could shed valuable insights into the design and preparation of various highly-open nanoframes with abundant exposed active species by using an etching-free strategy for efficient catalysis and beyond.
