Metal-Organic Frameworks (MOFs) And Their Composites In Capacitive Studies

Supercapacitors possess excellent power density,quick charge and discharge as well as a longer life than other chemical batteries,which have been widely concerned.In particular,the development of flexible electronic products has inspired people to explore more flexible,light-weight and environmentally friendly energy storage equipment.Flexible solid-state supercapacitors(SSCs)have many advantages,such as high power density,long cycle life,safety and efficiency,light mass and so on,thus are considered as prospective candidates for energy storage in the future.Metal-Organic framework materials(MOFs),also known as porous coordination polymers,are a promising class of crystalline microporous materials with super-high porosity,large internal surface area,adjustable structure and chemical composition and abundant active sites.Compared with traditional inorganic chemical materials,MOFs applied as electrode materials of supercapacitors show greater potential further improving the energy storage performance of supercapacitors.However,MOFs also show some drawbacks such as poor self-conductivity and chemical stability,which hinder the full realization of their potential as well as their applications in the field of energy storage.This paper aims to solve the problem of poor conductivity of MOFs materials by constructing composites of MOFs and some other conductive materials.One is to obtain different proportion of Co/Mn-RGO composites by one-pot solvothermal synthesis of graphene materials with excellent electrical conductivity and Co/Mn-MOF,and to investigate the effect of different proportion of graphene materials on the capacitive performance of the composites.The results show that the capacitance of Co/Mn-RGO-35 electrode can reach 271.2 m F·cm-2,which is is significantly higher than that of the Co/Mn-MOF electrode(41.1 m F·cm-2)at the scan rate of 5 m V·s-1.Our research has demonstrated that when 35 mg of graphene materials is introduced,the capacitance performance reaches the highest due to the synergistic effect of Co/Mn-MOF and RGO;The other is to introduce different sizes of CNT materials with excellent conductivity andstability combined with ZIF-8 to prepare ZIF-8/CNT composites,and then to obtain hybrid electrode materials by electrochemical deposition of conductive polymer polypyrrole,which aims to explore the effect of different sizes of CNT materials on the properties of the composites.The results show that ZIF-8/s CNT/PPy areal capacitance reaches 246.8 m F·cm-2 at a current density of 1 m A·cm-2,showing excellent areal capacitance.Moreover,when adjusting the content of s CNT(2 mg,4 mg,6 mg,8 mg)in ZIF-8/s CNT composites,it was found that ZIF-8/s CNT/PPy produced the highest capacitance performance at a content of 4 mg.