Although significant advances in the tailoring of nanocrystallite aggregates have been achieved,the synthesis of aggregates is strongly dependent on the use of templates,surfactants,and additives.Herein,direct rapid f...Although significant advances in the tailoring of nanocrystallite aggregates have been achieved,the synthesis of aggregates is strongly dependent on the use of templates,surfactants,and additives.Herein,direct rapid fabrication of ZnO nanoaggregates in a green and environmentally friendly polyol-H_(2)O medium is developed.Remarkably,the rapidly formed ZnO nanoaggregates can be engineered by controlling the types of polyols as well as the volume ratio of polyol to water.The amount of water in the nonaqueous polyol solution is the key to inducing the desired structure and surface areas of ZnO nanoaggregates.The variations in the crystal structure of ZnO nanoaggregates are investigated in detail by powder X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The effects of different ZnO structures on the catalytic capability are evaluated through photodegradation of ciprofloxacin(CIP)antibiotic under simulated solar light irradiation.The nanoparticle aggregates show the highest photocatalytic performance,and the photoinduced h^(+)and·OH are the predominant active species in the photocatalytic degradation of CIP.The enhancement of the photocatalytic capability of the ZnO nanoparticle aggregates compared to other nanostructures is mainly attributed to their unique structure,efficient electron-hole separation,and faster charge carrier transport,on the basis of photoluminescence spectra,photocurrent measurements,and electrochemical impedance spectroscopy.The polyol-mediated engineering of ZnO nanoaggregates could provide insights into the synthesis of other nanoaggregate-based single and hybrid functional structures.展开更多
A stepwise synthesis method was used to immobilize tetrachloro tetramethyl porphyrins in the supercages of NaCoX molecular sieve. The immobilized porphyrin was characterized by means of UV Vis, IR, DTA, SEM and E...A stepwise synthesis method was used to immobilize tetrachloro tetramethyl porphyrins in the supercages of NaCoX molecular sieve. The immobilized porphyrin was characterized by means of UV Vis, IR, DTA, SEM and EPR. A comparision was made for the activities among tetrachloro tetramethyl porphyrins, its cobalt(Ⅱ) complex, NaCoX molecular sieve and the immobilized porphyrin as catalysts in the oxidation reaction of styrene and p cresol. The stability and catalytic capability of the metalloporphyrin is increased after the combination of porphyrin with molecular sieve. In addition, this new type of catalyst tetrachloro tetramethyl porphyrin immobilized in the supercages of NaCoX molecular sieve not only possesses the advantages of both porphyrin and molecular sieve, but also makes up for their respective deficiencies. The experimental results confirmed that both the stability and catalytic capability of metalloporphyrin immobilized in the supercages of molecular sieve are increased.展开更多
The in situ electrophilic fluorination of phosphanes with commercially available bench-stable N-fluorobenzenesulfonimide(NFSI),followed by subsequent methylation of the[N(PhSO_(2))2]−anion with MeOTf yields a family o...The in situ electrophilic fluorination of phosphanes with commercially available bench-stable N-fluorobenzenesulfonimide(NFSI),followed by subsequent methylation of the[N(PhSO_(2))2]−anion with MeOTf yields a family of electrophilic fluorophosphonium cations as triflate salts.Most of these fluorophosphonium triflate salts are remarkably Lewis acidic and form isolable adducts in stoichiometric reactions with suitable donors such as N,N-dimethylformamide(DMF).Furthermore,their catalytic capabilities were tested in the transformation of formamides into N-sulfonyl formamidines in the reaction with Na[N(SO_(2)Ph)_(2)]and the proposed mechanism is validated by DFT calculations.展开更多
Although promising strategies have been developed to resolve the critical drawbacks of lithium-sulfur(Li-S)batteries,the intractable issues including undesirable shuttling of polysulfides and sluggish redox reaction k...Although promising strategies have been developed to resolve the critical drawbacks of lithium-sulfur(Li-S)batteries,the intractable issues including undesirable shuttling of polysulfides and sluggish redox reaction kinetics have still been unresolved thoroughly.Herein,a cobalt single-atom(CoSA)catalyst comprising of atomic Co distributed homogeneously within nitrogen(N)-doped porous carbon(Co-NPC)nanosphere is constructed and utilized as a separator coating in Li-S batteries.The Co-NPC exposes abundant active sites participating in sulfur redox reactions,and remarkable catalytic activity boosting the rapid polysulfide conversions.As a result,Li-S batteries with Co-NPC coating layer realize significantly enhanced specific capacity(1295 mAh·g^(-1)at 0.2 C),rate capability(753 mAh·g^(-1)at 3.0 C),and long-life cyclic stability(601 mAh·g^(-1)after 500 cycles at 1.0 C).Increasing the areal sulfur loading to 6.2 mg·cm^(-2),an extremely high areal capacity of 7.92 mAh·cm^(-2)is achieved.Further in situ X-ray diffraction,density functional theory calculations,and secondary ion mass spectrometry confirm the high catalytic capability of CoSA towards reversible polysulfide conversion.This study supplies new insights for adopting single-atom catalyst to upgrade the electrochemical performance of Li-S batteries.展开更多
基金Support from the Australian Research Council(ARC)through ARC Discovery projects(DP 130102274,DP130102699,DP160102627)is gratefully acknowledgedthe National Natural Science Foundation of China(21501137)the Hubei Provincial Natural Science Foundation(2018CFB680)for financial support。
文摘Although significant advances in the tailoring of nanocrystallite aggregates have been achieved,the synthesis of aggregates is strongly dependent on the use of templates,surfactants,and additives.Herein,direct rapid fabrication of ZnO nanoaggregates in a green and environmentally friendly polyol-H_(2)O medium is developed.Remarkably,the rapidly formed ZnO nanoaggregates can be engineered by controlling the types of polyols as well as the volume ratio of polyol to water.The amount of water in the nonaqueous polyol solution is the key to inducing the desired structure and surface areas of ZnO nanoaggregates.The variations in the crystal structure of ZnO nanoaggregates are investigated in detail by powder X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The effects of different ZnO structures on the catalytic capability are evaluated through photodegradation of ciprofloxacin(CIP)antibiotic under simulated solar light irradiation.The nanoparticle aggregates show the highest photocatalytic performance,and the photoinduced h^(+)and·OH are the predominant active species in the photocatalytic degradation of CIP.The enhancement of the photocatalytic capability of the ZnO nanoparticle aggregates compared to other nanostructures is mainly attributed to their unique structure,efficient electron-hole separation,and faster charge carrier transport,on the basis of photoluminescence spectra,photocurrent measurements,and electrochemical impedance spectroscopy.The polyol-mediated engineering of ZnO nanoaggregates could provide insights into the synthesis of other nanoaggregate-based single and hybrid functional structures.
文摘A stepwise synthesis method was used to immobilize tetrachloro tetramethyl porphyrins in the supercages of NaCoX molecular sieve. The immobilized porphyrin was characterized by means of UV Vis, IR, DTA, SEM and EPR. A comparision was made for the activities among tetrachloro tetramethyl porphyrins, its cobalt(Ⅱ) complex, NaCoX molecular sieve and the immobilized porphyrin as catalysts in the oxidation reaction of styrene and p cresol. The stability and catalytic capability of the metalloporphyrin is increased after the combination of porphyrin with molecular sieve. In addition, this new type of catalyst tetrachloro tetramethyl porphyrin immobilized in the supercages of NaCoX molecular sieve not only possesses the advantages of both porphyrin and molecular sieve, but also makes up for their respective deficiencies. The experimental results confirmed that both the stability and catalytic capability of metalloporphyrin immobilized in the supercages of molecular sieve are increased.
基金supported by the Sino-German Collaboration of the German Science foundation(Project No.WE4621/4-1/392417756)the TUD.Chun-Xiang Guo thanks China Scholarship Council(CSC No.201506200056)for a scholarshipthe MICIU/AEI from Spain for financial support(Project CTQ2017-85821-R,Feder funds).
文摘The in situ electrophilic fluorination of phosphanes with commercially available bench-stable N-fluorobenzenesulfonimide(NFSI),followed by subsequent methylation of the[N(PhSO_(2))2]−anion with MeOTf yields a family of electrophilic fluorophosphonium cations as triflate salts.Most of these fluorophosphonium triflate salts are remarkably Lewis acidic and form isolable adducts in stoichiometric reactions with suitable donors such as N,N-dimethylformamide(DMF).Furthermore,their catalytic capabilities were tested in the transformation of formamides into N-sulfonyl formamidines in the reaction with Na[N(SO_(2)Ph)_(2)]and the proposed mechanism is validated by DFT calculations.
基金financially supported by the National Natural Science Foundation of China(No.22005003)the Natural Science Research Project of Anhui Province Education Department(Nos.2022AH030046 and 2022AH050334)+2 种基金the Yong Scientific Foundation of Anhui University of Technology for Top Talent(No.DT2100000947)the Scientific Research Foundation of Anhui University of Technology for Talent Introduction(No.DT19100069)The theoretical simulations were carried out at Shanxi Supercomputing Center of China,and performed on TianHe-2.
文摘Although promising strategies have been developed to resolve the critical drawbacks of lithium-sulfur(Li-S)batteries,the intractable issues including undesirable shuttling of polysulfides and sluggish redox reaction kinetics have still been unresolved thoroughly.Herein,a cobalt single-atom(CoSA)catalyst comprising of atomic Co distributed homogeneously within nitrogen(N)-doped porous carbon(Co-NPC)nanosphere is constructed and utilized as a separator coating in Li-S batteries.The Co-NPC exposes abundant active sites participating in sulfur redox reactions,and remarkable catalytic activity boosting the rapid polysulfide conversions.As a result,Li-S batteries with Co-NPC coating layer realize significantly enhanced specific capacity(1295 mAh·g^(-1)at 0.2 C),rate capability(753 mAh·g^(-1)at 3.0 C),and long-life cyclic stability(601 mAh·g^(-1)after 500 cycles at 1.0 C).Increasing the areal sulfur loading to 6.2 mg·cm^(-2),an extremely high areal capacity of 7.92 mAh·cm^(-2)is achieved.Further in situ X-ray diffraction,density functional theory calculations,and secondary ion mass spectrometry confirm the high catalytic capability of CoSA towards reversible polysulfide conversion.This study supplies new insights for adopting single-atom catalyst to upgrade the electrochemical performance of Li-S batteries.
