Preparation And Capacitive Properties Of Co-MOF/carbon Cloth Composite Electrodes

Supercapacitors have important application value in the field of energy storage and conversion.Among numerous electrode materials,MOFs materials have received extensive attention as promising electrode materials for supercapacitors due to their simple synthesis method,controllable structure and large specific surface area.However,owing to the structure instability and poor conductivity,MOFs display poor cycle stability and rate capability.In this work,two kinds of cobalt-based MOF material were grown on carbon cloth substrates by simple and reliable methods to improve the conductivity and stability of MOFs.The obtained materials were characterized by SEM,XRD,XPS and FTIR.And the electrochemical performances were investigated in the three-electrode system and the two-electrode system of asymmetric all-solid-state supercapacitor.The main research results are shown as follows:(1)Cobalt-based MOF(Co₃(BTC)₂·12H₂O,Co-MOF)was directly deposited on the Co-modified carbon cloth substrate(CC)by cathodic electrodeposition in a two-electrode system using 1,3,5-benzoic acid and Co(NO₃)₂·6H₂O as organic ligand and metal source.The electrochemical results in three-electrode system showed that the Co-MOF/CC electrode had an area specific capacitance of 1784 m F/cm~2 and a mass specific capacitance of 137 F/g at a current density of 1 m A/cm~2,a high capacitance retention of 72%after 10000 cycles at a current density of 5 m A/cm~2,as well as good rate capability and impedance characteristics.The asymmetric all-solid-state supercapacitor using Co-MOF/CC and activated carbon as the positive electrode and negative electrode delivered an energy density of 23.1 Wh/kg at a power density of385.3 W/kg,as well as a small contact resistance and ion transfer diffusion resistance.(2)The Co-modified carbon cloth substrate(Co/CC)was immersed in 2-methylimidazole solution and reacted at room temperature to prepare ZIF-67/CC(a)composite electrode.For comparison,C_O(NO₃)₂·6H₂O was added to 2-methylimidazole solution to supplement Co source to prepare ZIF-67/CC(b)composite electrode.The electrochemical results showed that when the current density was 1m A/cm~2,the area specific capacitances of ZIF-67/CC(a)and ZIF-67/CC(b)were 1470and 3396 m F/cm~2,and the mass specific capacitances were 225 F/g and 263 F/g,respectively.Both electrodes maintained more than 90%of the initial capacity after10000 cycles at a current density of 5 m A/cm~2.The asymmetric all-solid-state supercapacitor using ZIF-67/CC(b)and activated carbon as the positive electrode and negative electrode showed an energy density of 20.3 Wh/kg at a power density of 420.2W/kg,small impedance characteristics and good rate capability.