Comparative Electrochemical Performance of ZIF‐8, ZIF‐67, and ZIF‐L for Supercapacitor Applications on FTO Substrates

ABSTRACT Supercapacitors had gained attention as efficient energy storage systems due to their ability to deliver high power density, fast charge‐discharge rates, and long operational lifespan. Among the various electrode materials explored, metal‐organic frameworks (MOFs), especially zeolitic imidazolate frameworks (ZIFs) stood out because of their large surface area, adjustable porosity, and structural adaptability. In this work, ZIF‐8, ZIF‐67, and ZIF‐L were successfully synthesized through a simple solution‐based approach. For the first time, the electrochemical performance of these three ZIFs was systematically compared using fluorine‐doped tin oxide (FTO) substrates as current collectors, which revealed both material behavior and substrate limitations. Their structural, optical, and surface features were studied using x‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), UV–visible spectroscopy, and scanning electron microscopy (SEM). These ZIF materials were then deposited onto FTO substrates to evaluate their electrochemical performance through cyclic voltammetry (CV), galvanostatic charge‐discharge (GCD), and electrochemical impedance spectroscopy (EIS). While ZIF‐67 showed the highest specific capacitance of 27.61 F/g at 0.1 A/g, overall performance remained limited due to FTO's poor conductivity and inadequate interfacial bonding. The study highlighted FTO's limitations as a current collector in ZIF‐based supercapacitor applications.