Controllable Preparation And Electrochemical Performances Of Bismuth-Based MOFs-Derived Nanomaterials

In recent years,with the rapid development of science and technology and the wide application of mobile electronics,a lot of research is devoted to the storage of electric energy.Supercapacitors(SCs)is a new type of electrochemical capacitor between traditional capacitor and battery,which has the advantages of high power density,long cycle life,wide operating temperature range,low maintenance cost and no pollution.The influence of electrode material on the performance of SCs is very important,especially the negative material,so it is still a great challenge to study the SCs negative material with high capacity and long cycle life.Bismuth(Bi)metal is emerging as an attractive anode material in aqueous electrolyte energy storage equipment because of its highly reversible redox reaction,wide negative working window in aqueous electrolyte,inexpensive and eco-friendly nature.Metal organic frameworks(MOFs)is an organic-inorganic hybrid material with structural diversity and functional diversity,which is widely used in various electrode materials.At the same time,MOFs as a sacrificial template can not only retain the structural characteristics of MOFs materials but also have the characteristics of inorganic substances,is considered as an effective way to obtain excellent electrode materials with high reversible capacity and high cycling performance.Therefore,this paper is devoted to the studying of Bismuth-based MOF(Bi-MOF)and their derivatives applied to the negative electrode properties of SCs.The content mainly includes the following parts:Bismuth ion with high oxidation state makes Bi-MOF have high structural stability,especially the Bi-MOF with pore structure can be used in a wider range.We successfully prepared a hexagonal prism CAU-17 by a simple solvothermal method using bismuth nitrate pentahydrate and trimesic acid in a methanol solution.The obtained CAU-17 has a large specific surface area and a microporous structure,and was used as the negative material of SCs to test its electrochemical performance.The specific capacity was 381 C g^-1 at a current density of 0.5 A g^-1,revealing that CAU-17 has good electrochemical energy storage characteristics.Bi-MOF is expected to be one of the candidate materials for SCs negative electrodes.Bismuth sulfide(Bi₂S₃)as a new species of negative electrode materials for SCs has attracted much attention due to its unique lamellar structure,various morphology,rapid redox behaviour and environmental friendliness.However,the design and fabrication of hierarchically hollow structures for Bi₂S₃ electrode materials through a facile approach remain a huge challenge.We preparation a unique hierarchically hollow Bi₂S₃ negative electrode material for SCs derived from the CAU-17through a facile self-sacrificing templated strategy.The resulted Bi₂S₃ nanorods-stacked hollow microtubes exhibit large specific surface area(54.3 m² g^-1)and ultrahigh specific capacitance(709F g^-1at 1 A g^-1).Moreover,a hybrid supercapacitor(HSC)device using a layered double hydroxide(Co Ni-LDH)as positive electrode deliver excellent energy density of 24.1 Wh kg^-1 at power density of 700.0 W kg^-1.Consequently,this work may provide guidelines to successful design of porous Bi₂S₃ for exploring high-performance anode materials and energy-related applications.Nano-carbon or metal compounds/composites derived from MOFs as sacrificial templates are considered to be excellent electrode materials due to their high reversibility and high cycling performance.Especially,the direct formation of carbon-doped composites can improve the conductivity and stability,which can ensure the rapid transfer of electrons.Herein,we report a Bi₂O₃@C microrod through a facile one-step heat treatment,using CAU-17 as both template and precursor.Benefiting from the carbon coated layer from the pyrolysis of CAU-17,it can increase the electrical conductivity and ease the volume collapse during the discharge–charge process.The obtained Bi₂O₃@C hybrid as negative electrode for SCs exhibits ultrahigh specific capacity(1378C g^-1 at 0.5 A g^-1)and excellent cycling stability(93%retention at 4000 cycles).In addition,asymmetric supercapacitor(ASC)device using a layered double hydroxide(Co Ni-LDH)as positive electrode provides a high energy density of 49 Wh kg^-1 at a power density of 807 W kg^-1.In conclusion,the paper is devoted to regulating and synthesizing novel Bi-MOF materials,and seeking the best conversion method to transform MOF into metal sulfide/oxide,which can be used as a negative electrode material to improve the electrochemical properties of materials.