Two-dimensional Fe-MOF and bimetallic NiFe-MOFs with different Ni : Fe ratios for superior electrochemical performance in supercapacitor applications

Abstract

Supercapacitors (SCs) are garnering significant attention owing to their remarkable power density. Transition-metal-based MOFs have abundant valence states, which contribute to their superior stability, high energy density, and high power density. In this study, monometallic Fe-BDC MOF and bimetallic NiFe-BDC MOFs were synthesized with different molar ratios and examined for their application in supercapacitors. SEM-coupled EDX, BET, and XRD analyses were performed to determine their morphologies and microstructures. The electrodes were evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements in a 1 M KOH aqueous electrolyte. The Ni₁₀Fe₁-BDC MOF electrode exhibited the highest capacitance (918.75 F g⁻¹) at 4 A g⁻¹ due to its fast ion transport and low electrical resistance, resulting from its spherical structure. The Ni₁₀Fe₁-BDC MOF//Ni₁₀Fe₁-BDC MOF symmetric supercapacitor accomplished a high energy density of 106.42 Wh kg⁻¹ at a power density of 3720 W kg⁻¹ and exhibited a high rate capability of 137.73% after 2000 cycles, indicating its potential in supercapacitor applications.