MXenes are two-dimensional transition metal carbides and/or nitrides with unique physiochemical properties and have attracted extensive interest in numerous fields.However,current MXene synthesis methods are limited b...MXenes are two-dimensional transition metal carbides and/or nitrides with unique physiochemical properties and have attracted extensive interest in numerous fields.However,current MXene synthesis methods are limited by hazardous synthesis conditions,high production costs,or difficulty in largescale production.Therefore,a general,safe,cost-effective,and scalable synthesis method for MXenes is crucial.Here,we report the fast synthesis of MXenes in the open air using a molten salt-shielded synthesis(MS^(3))method,which uses Lewis-acid salts as etchants and a low-melting-point eutectic salt mixture as the reaction medium and shield to prevent MXene oxidation at high temperatures.Carbide and nitride MXenes,including Ti_(3)C_(2)T_(x),Ti_(2)CT_(x),Ti_(3)CNT_(x),and Ti_(4)N_(3)T_(x),were successfully synthesized using the MS^(3) method.We also present the flexibility of the MS^(3) method by scaling the etching process to large batches of 20 and 60 g of Ti_(3)AlC_(2) MAX precursor in one pot.When used as negative electrodes,the prepared MS^(3)-MXenes delivered excellent electrochemical properties for high-rate Li-ion storage.展开更多
The study of pickling of the EL21T6 substrate in a nitric acid bath firstly provided knowledge of the influence of the different experimental parameters(concentration of acid,temperature and stirring of the solution)i...The study of pickling of the EL21T6 substrate in a nitric acid bath firstly provided knowledge of the influence of the different experimental parameters(concentration of acid,temperature and stirring of the solution)in relation to the etching rate.This experimental part led to the choice of standard pickling(T_(bath)=25℃,moderate stirring(250 rpm),[HNO_(3)]=1.20 mol/L,duration of 2 min)so as to obtain constant removal of material,even after several uses of the pickling bath.SEM observations also confirmed that in these operating conditions,pickling concerns both the grains of the matrix and the precipitates of type Mg3(Nd,Gd),leading to uniform removal of material from the surface.Working from a number of assumptions,thermodynamic and chemical kinetic studies then allowed a pickling mechanism to be proposed and led to obtaining values for the corresponding kinetic parameters(order of reaction,constant of mean rate,activation energy)to be obtained.展开更多
Recently,multivalent aqueous calcium-ion batteries(CIBs)have attracted considerable attention as a possible alternative to Li-ion batteries.However,traditional Ca-ion storage materials show either limited rate capabil...Recently,multivalent aqueous calcium-ion batteries(CIBs)have attracted considerable attention as a possible alternative to Li-ion batteries.However,traditional Ca-ion storage materials show either limited rate capabilities and poor cycle life or insufficient specific capacity.Here,we tackle these limitations by exploring materials having a large interlayer distance to achieve decent specific capacities and one-dimensional architecture with adequate Ca-ion passages that enable rapid reversible(de)intercalation processes.In this work,we report the high-yield,rapid,and low-cost synthesis of 1D metal oxides MV_(3)O_(8)(M=Li,K),CaV_(2)O_(6),and CaV_(6)O_(16)·7H_(2)O(CVO)via a molten salt method.Firstly,using 1D CVO as electrode materials,we show high capacity 205 mA h g^(-1),long cycle life(>97%capacity retention after 200 cycles at 3.0 C),and high-rate performance(117 mA h g^(-1) at 12 C)for Ca-ion(de)intercalation.This work represents a step forward for the development of the molten salt method to synthesize nanomaterials and to help pave the way for the future growth of Ca-ion batteries.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52072252,No.51902215)Sichuan Science and Technology Program(No.2020ZDZX0005)+4 种基金the Fundamental Research Funds for the Central Universities(YJ201886)the Agence Nationale de la Recherche(Labex STORE-EX)for financial supportsupported by the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(Grant No.2019R01003)Ningbo Top-talent Team Program,Ningbo Municipal Bureau of Science and Technology(Grant No.2018A610005)President’s International Fellowship Initiative of CAS(No.2021DE0002).
文摘MXenes are two-dimensional transition metal carbides and/or nitrides with unique physiochemical properties and have attracted extensive interest in numerous fields.However,current MXene synthesis methods are limited by hazardous synthesis conditions,high production costs,or difficulty in largescale production.Therefore,a general,safe,cost-effective,and scalable synthesis method for MXenes is crucial.Here,we report the fast synthesis of MXenes in the open air using a molten salt-shielded synthesis(MS^(3))method,which uses Lewis-acid salts as etchants and a low-melting-point eutectic salt mixture as the reaction medium and shield to prevent MXene oxidation at high temperatures.Carbide and nitride MXenes,including Ti_(3)C_(2)T_(x),Ti_(2)CT_(x),Ti_(3)CNT_(x),and Ti_(4)N_(3)T_(x),were successfully synthesized using the MS^(3) method.We also present the flexibility of the MS^(3) method by scaling the etching process to large batches of 20 and 60 g of Ti_(3)AlC_(2) MAX precursor in one pot.When used as negative electrodes,the prepared MS^(3)-MXenes delivered excellent electrochemical properties for high-rate Li-ion storage.
文摘The study of pickling of the EL21T6 substrate in a nitric acid bath firstly provided knowledge of the influence of the different experimental parameters(concentration of acid,temperature and stirring of the solution)in relation to the etching rate.This experimental part led to the choice of standard pickling(T_(bath)=25℃,moderate stirring(250 rpm),[HNO_(3)]=1.20 mol/L,duration of 2 min)so as to obtain constant removal of material,even after several uses of the pickling bath.SEM observations also confirmed that in these operating conditions,pickling concerns both the grains of the matrix and the precipitates of type Mg3(Nd,Gd),leading to uniform removal of material from the surface.Working from a number of assumptions,thermodynamic and chemical kinetic studies then allowed a pickling mechanism to be proposed and led to obtaining values for the corresponding kinetic parameters(order of reaction,constant of mean rate,activation energy)to be obtained.
基金This work was supported by the French Agence Nationale de la Recherche(Labex STOREX program)L.Liu is supported by the China Scholarship Council(CSC).
文摘Recently,multivalent aqueous calcium-ion batteries(CIBs)have attracted considerable attention as a possible alternative to Li-ion batteries.However,traditional Ca-ion storage materials show either limited rate capabilities and poor cycle life or insufficient specific capacity.Here,we tackle these limitations by exploring materials having a large interlayer distance to achieve decent specific capacities and one-dimensional architecture with adequate Ca-ion passages that enable rapid reversible(de)intercalation processes.In this work,we report the high-yield,rapid,and low-cost synthesis of 1D metal oxides MV_(3)O_(8)(M=Li,K),CaV_(2)O_(6),and CaV_(6)O_(16)·7H_(2)O(CVO)via a molten salt method.Firstly,using 1D CVO as electrode materials,we show high capacity 205 mA h g^(-1),long cycle life(>97%capacity retention after 200 cycles at 3.0 C),and high-rate performance(117 mA h g^(-1) at 12 C)for Ca-ion(de)intercalation.This work represents a step forward for the development of the molten salt method to synthesize nanomaterials and to help pave the way for the future growth of Ca-ion batteries.
