Sophisticated efficient electrocatalysts are essential to rectifying the shuttle effect and realizing the high performance of flexible lithium-sulfur batteries(LSBs).Phase transformation of MoSe_(2) from the 2H phase ...Sophisticated efficient electrocatalysts are essential to rectifying the shuttle effect and realizing the high performance of flexible lithium-sulfur batteries(LSBs).Phase transformation of MoSe_(2) from the 2H phase to the 1T phase has been proven to be a significant method to improve the catalytic activity.However,precisely controllable phase engineering of MoSe_(2) has rarely been reported.Herein,by in situ Li ions intercalation in MoSe_(2),a precisely controllable phase evolution from 2H-MoSe_(2) to 1T-MoSe_(2) was realized.More importantly,the definite functional relationship between cut-off voltage and phase structure was first identified for phase engineering through in situ observation and modulation methods.The sulfur host(CNFs/1T-MoSe_(2))presents high charge density,strong polysulfides adsorption,and catalytic kinetics.Moreover,Li-S cells based on it display capacity retention of 875.3mAh g^(-1) after 500 cycles at 1 C and an areal capacity of 8.71mAh cm^(-2) even at a high sulfur loading of 8.47mg cm^(-2).Furthermore,the flexible pouch cell exhibiting decent performance will endow a promising potential in the wearable energy storage field.This study proposes an effective strategy to precisely control the phase structure of MoSe_(2),which may provide the reference to fabricate the highly efficient electrocatalysts for LSBs and other energy systems.展开更多
Using the Lyapunov function method,this paper investigates the design of state feedback stabilization controllers for fractional order nonlinear systems in triangular form,and presents a number of new results.First,so...Using the Lyapunov function method,this paper investigates the design of state feedback stabilization controllers for fractional order nonlinear systems in triangular form,and presents a number of new results.First,some new properties of Caputo fractional derivative are presented,and a sufficient condition of asymptotical stability for fractional order nonlinear systems is obtained based on the new properties.Then,by introducing appropriate transformations of coordinates,the problem of controller design is converted into the problem of finding some parameters,which can be certainly obtained by solving the Lyapunov equation and relevant matrix inequalities.Finally,based on the Lyapunov function method,state feedback stabilization controllers making the closed-loop system asymptotically stable are explicitly constructed.A simulation example is given to demonstrate the effectiveness of the proposed design procedure.展开更多
Proper regulation of metal-nitrogen carbon(M-N-C)materials derived from zeolitic imidazolate frameworks(ZIFs)is essential to enhance the oxygen reduction reaction(ORR)performance.However,most of the reports focus on t...Proper regulation of metal-nitrogen carbon(M-N-C)materials derived from zeolitic imidazolate frameworks(ZIFs)is essential to enhance the oxygen reduction reaction(ORR)performance.However,most of the reports focus on the component regulation,and the structure regulation of ZIFs-derived M-N-C materials by a simple preparation method has been barely reported.Herein,using a one-step electrospinning method with subsequent pyrolysis,we have prepared a bead-like cobalt-nitrogen co-doped carbon nanocage/carbon nanofiber(Co-N-C/CNF)composite electrocatalyst with the porous carbon nanocages arranged one by one in the highly conductive carbon nanofibers.Profiting from the fully exposed active sites and improved conductivity,the Co-NC/CNF catalyst exhibits an excellent ORR performance even surpassing the commercial Pt/C catalyst.Density functional theory(DFT)results demonstrate that the CoNP-N1-C2 active sites on Co-N-C/CNF make the core contribution to the improvement of ORR properties.Moreover,the zinc-air battery(ZAB)based on the Co-N-C/CNF catalyst also shows outstanding discharge performance.This study provides a new strategy for the preparation and structural design for ZIFs-derived M-N-C materials as efficient ORR catalysts.展开更多
Developing a selective hydrogenation strategy over a low-cost electrocatalyst,especially with an inexpensive and safe hydrogen source for efficient synthesis of aminoareneswith fragile functional groups,is extremely d...Developing a selective hydrogenation strategy over a low-cost electrocatalyst,especially with an inexpensive and safe hydrogen source for efficient synthesis of aminoareneswith fragile functional groups,is extremely desirable.Herein,using H_(2)O as the hydrogen source,Ti mesh-supported Co_(3)S_(4)ultrathin nanosheets with sulfur vacancies(denoted as Co_(3)S_(4−x)NS)have been demonstrated to be a highly efficient cathode for selective transfer hydrogenation of nitroarenes to corresponding aminoarenes at low potential.D_(2)O-labeling experiments confirmed the hydrogen origin.Without sulfur vacancies,the products were a mixture of aminoarenes and azoxyareneswith lowselectivity.This method can deliver a variety of aminoarenes with outstanding selectivity and excellent functional group compatibility with highly reducible groups(e.g.,C–I,C–Br,C=O,C=C,C=N,C≡N,and C≡C).The experimental and theoretical results have revealed that sulfur vacancies can enhance the selective specific adsorption of the nitro group and promote intrinsic activity to form active hydrogen from water electrolysis,thus resulting in high selectivity and outstanding fragile functional groups tolerance.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:U2004172,51972287 and 51502269the Foundation for University Key Teachers of Henan Province,Grant/Award Number:2020GGJS009Natural Science Foundation of Henan Province,Grant/Award Number:202300410368。
文摘Sophisticated efficient electrocatalysts are essential to rectifying the shuttle effect and realizing the high performance of flexible lithium-sulfur batteries(LSBs).Phase transformation of MoSe_(2) from the 2H phase to the 1T phase has been proven to be a significant method to improve the catalytic activity.However,precisely controllable phase engineering of MoSe_(2) has rarely been reported.Herein,by in situ Li ions intercalation in MoSe_(2),a precisely controllable phase evolution from 2H-MoSe_(2) to 1T-MoSe_(2) was realized.More importantly,the definite functional relationship between cut-off voltage and phase structure was first identified for phase engineering through in situ observation and modulation methods.The sulfur host(CNFs/1T-MoSe_(2))presents high charge density,strong polysulfides adsorption,and catalytic kinetics.Moreover,Li-S cells based on it display capacity retention of 875.3mAh g^(-1) after 500 cycles at 1 C and an areal capacity of 8.71mAh cm^(-2) even at a high sulfur loading of 8.47mg cm^(-2).Furthermore,the flexible pouch cell exhibiting decent performance will endow a promising potential in the wearable energy storage field.This study proposes an effective strategy to precisely control the phase structure of MoSe_(2),which may provide the reference to fabricate the highly efficient electrocatalysts for LSBs and other energy systems.
基金supported by National Natural Science Foundation of China(61374065,61374002,61503225,61573215)the Research Fund for the Taishan Scholar Project of Shandong Province of Chinathe Natural Science Foundation of Shandong Province(ZR2015FQ003)
文摘Using the Lyapunov function method,this paper investigates the design of state feedback stabilization controllers for fractional order nonlinear systems in triangular form,and presents a number of new results.First,some new properties of Caputo fractional derivative are presented,and a sufficient condition of asymptotical stability for fractional order nonlinear systems is obtained based on the new properties.Then,by introducing appropriate transformations of coordinates,the problem of controller design is converted into the problem of finding some parameters,which can be certainly obtained by solving the Lyapunov equation and relevant matrix inequalities.Finally,based on the Lyapunov function method,state feedback stabilization controllers making the closed-loop system asymptotically stable are explicitly constructed.A simulation example is given to demonstrate the effectiveness of the proposed design procedure.
基金The work was supported by the National Natural Science Foundation of China(Nos.52104314,51972287,U2004172,and 51502269)Natural Science Foundation of Henan Province(No.202300410368)+2 种基金the Special Project of Key Research Development and Promotion of Henan Province(No.222102240084)Sponsored by Program for Science&Technology Innovation Talents in Universities of Henan Province(23HASTIT001)the Foundation for University Key Teachers of Henan Province(No.2020GGJS009).
文摘Proper regulation of metal-nitrogen carbon(M-N-C)materials derived from zeolitic imidazolate frameworks(ZIFs)is essential to enhance the oxygen reduction reaction(ORR)performance.However,most of the reports focus on the component regulation,and the structure regulation of ZIFs-derived M-N-C materials by a simple preparation method has been barely reported.Herein,using a one-step electrospinning method with subsequent pyrolysis,we have prepared a bead-like cobalt-nitrogen co-doped carbon nanocage/carbon nanofiber(Co-N-C/CNF)composite electrocatalyst with the porous carbon nanocages arranged one by one in the highly conductive carbon nanofibers.Profiting from the fully exposed active sites and improved conductivity,the Co-NC/CNF catalyst exhibits an excellent ORR performance even surpassing the commercial Pt/C catalyst.Density functional theory(DFT)results demonstrate that the CoNP-N1-C2 active sites on Co-N-C/CNF make the core contribution to the improvement of ORR properties.Moreover,the zinc-air battery(ZAB)based on the Co-N-C/CNF catalyst also shows outstanding discharge performance.This study provides a new strategy for the preparation and structural design for ZIFs-derived M-N-C materials as efficient ORR catalysts.
基金supported by the National Natural Science Foundation of China(no.21871206).
文摘Developing a selective hydrogenation strategy over a low-cost electrocatalyst,especially with an inexpensive and safe hydrogen source for efficient synthesis of aminoareneswith fragile functional groups,is extremely desirable.Herein,using H_(2)O as the hydrogen source,Ti mesh-supported Co_(3)S_(4)ultrathin nanosheets with sulfur vacancies(denoted as Co_(3)S_(4−x)NS)have been demonstrated to be a highly efficient cathode for selective transfer hydrogenation of nitroarenes to corresponding aminoarenes at low potential.D_(2)O-labeling experiments confirmed the hydrogen origin.Without sulfur vacancies,the products were a mixture of aminoarenes and azoxyareneswith lowselectivity.This method can deliver a variety of aminoarenes with outstanding selectivity and excellent functional group compatibility with highly reducible groups(e.g.,C–I,C–Br,C=O,C=C,C=N,C≡N,and C≡C).The experimental and theoretical results have revealed that sulfur vacancies can enhance the selective specific adsorption of the nitro group and promote intrinsic activity to form active hydrogen from water electrolysis,thus resulting in high selectivity and outstanding fragile functional groups tolerance.
