Designing compositionally driven Cu-NiFe2O4 based electrodes for high-performance supercapacitors

The presence of polymer binders in conventional powder-based electrodes often increases interfacial resistance and hinders electrochemical performance by blocking electrochemically active sites. To address this issue, we report the synthesis of binder-free Cu-substituted NiFe 2 O 4 (Ni 1-x Cu x Fe 2 O 4 , x = 0, 0.25, 0.5, 0.75, and 1) via a simple reflux condensation route. The influence of Cu/Ni molar ratios on the structural, morphological, and electrochemical properties of NiFe 2 O 4 was thoroughly examined. X-Ray Diffraction (XRD) and Fourier Transform Infra-red spectroscopy confirm the formation of a single-phase cubic spinel structure of the material. Scanning Electron Microscopy (SEM) revealed the formation of hierarchical structures. Energy Dispersive Spectroscopy (EDS) and X-Ray Photo-electron Spectroscopy validate the elemental composition and chemical state of the material. Electrochemical evaluation in 1 M KOH reveals that 50% Cu-substituted NiFe 2 O 4 achieved the highest capacitance of 907 Fg −1 , at a current density of 1 Ag −1 . A symmetric device based on the optimized electrode delivers an energy density of 27 Wh kg −1 at a power density of 1200 W kg −1 and successfully powered a light-emitting diode (LED). This work demonstrates how thoughtfully engineered materials can become impactful materials, designed not just for science but for building a sustainable world.