High Conductivity and Surface‐Activated Calcium Ferrite–Carbon Nanotube Composites for Advanced Supercapacitor Applications

ABSTRACT Advancements in electrode materials with a high potential window and elevated energy density are essential to meet the growing demands of high‐performance supercapacitors. Ferrites are a promising family of electrode materials. Among them, calcium ferrite (CaFe 2 O 4 ) has excellent structural stability. However, the low specific capacitance and high agglomeration rate of CaFe 2 O 4 limit its applications. The addition of carbonaceous material to the ferrite host matrix is expected to modify the supercapacitor electrode characteristics. CaFe 2 O 4 has not been explored yet as a composite of CNTs. In this work, robust (CaFe 2 O 4 ) 1‐x (CNTs) x nanocomposites are synthesized through a simple sol–gel method via an ex‐situ approach with extraordinary electrochemical properties. The prepared nanocomposites have unambiguously shown a polycrystalline nature, defective vibrational bonding, and a tuned band gap towards the low‐frequency region due to the formation of heterojunctions, confirmed through XRD, FTIR, XPS, UV, and PL. The electrochemical studies reveal that the (CaFe 2 O 4 ) 0.8 (CNTs) 0.2 nanocomposites have the highest specific capacitance of 530.54 Fg −1 at 0.5 Ag −1 with the lowest ohmic and solution resistance, along with remarkable cyclic stability and columbic efficiency, making them an efficient electrode material.