Solvent-free MOF-CVD prepared ZIF-67 film with hollow and opened morphology for supercapacitor application

Abstract

Metal organic frameworks (MOFs) have demonstrated excellent properties for application in energy storage field. In this work, we use a facile and solvent-free method to fabricate ZIF-67 films on foam Ni, Cu, Fe and Zn substrates. The pre-electrodeposited films are exposed to 2-methylimidazole vapor to generate ZIF-67 films. The morphology of the ZIF-67 films depends on the substrates and reaction duration. Specially, a hollow and opened polyhedron appearance is generated on the foam Ni substrate, which presents a uniform and smooth distribution. All ZIF-67 films on different substrates demonstrate good electrochemical performances when they are utilized as the active materials in the supercapacitors. The ZIF-67 film on the foam Ni substrate has 105 mF/cm2 areal specific capacitance at 10 mA/cm2 current density, showing superior electrochemical properties than that on other substrates. The specific energy can reach 24.5 μWh/cm2 at a high specific power of 14 mW/cm2 in an asymmetric supercapacitor, with Ni@Z67 as the cathode material and active carbon as anode electrode material. The process combining a simple electrodeposition method with solvent-free CVD transformation will be useful for the fabrication of MOFs films and their potential applications in various fields.