Optimized Fabrication of Supercapacitor Using MOF-Derived NiCo₂O₄ with Porous Carbon as Cathode: Electrochemical Characterization and Stability Analysis using Time Series Analysis Technique

This study utilizes metal–organic framework (MOF)-derived NiCo 2 O 4 with porous carbon (PC) as the cathode to fabricate both symmetric and asymmetric supercapacitor devices with an optimized anode (NiCo 2 O 4 /PC, activated carbon (AC), polyaniline (PANI)) and aqueous electrolytes. Initially, NiCo 2 O 4 /PC material was synthesized from a bimetallic–organic framework (NiCo-BTC MOF) using carefully optimized thermal conditions. Following comprehensive characterizations, the NiCo 2 O 4 /PC material was employed as a cathode material in the fabrication of solid-state supercapacitor devices by meticulously selecting an electrode–electrolyte pair to maximize supercapacitor performance. To achieve this, electrochemical characterizations of NiCo 2 O 4 /PC/NF (NF: Ni foam) were carried out in various aqueous electrolytes. The 1.0 M potassium hydroxide (KOH) electrolyte demonstrated the most promising electrochemical performance for the NiCo 2 O 4 /PC/NF composite. Subsequently, a KOH-based gel electrolyte was employed to evaluate the performance of three supercapacitor devices. These included two asymmetric devices, NiCo 2 O 4 /PC/NF–AC/NF and NiCo 2 O 4 /PC/NF–PANI/NF, as well as one symmetric device, NiCo 2 O 4 /PC/NF–NiCo 2 O 4 /PC/NF. Notably, the NiCo 2 O 4 /PC/NF–PANI/NF device exhibited an energy density almost 3.23 and 3.78 times higher than those of the NiCo 2 O 4 /PC/NF-NiCo 2 O 4 /PC/NF and NiCo 2 O 4 /PC/NF–AC/NF devices, respectively. The long-term stability of a system, analyzed over 2000 charge–discharge cycles using time series analysis, reveals insights into its performance and behavior over an extended duration. This illustrated the efficacy of PANI as an anode (instead of AC) with MOF-derived NiCo 2 O 4 /PC as the cathode material. Furthermore, the aforementioned high-performing supercapacitor was integrated in series to power an LED, demonstrating its practical applicability.