Facile, Cost Effective and Eco‐friendly Approach to Synthesize Bio‐MnO2 Nanosphered Thin Filmfor all Solid‐State Flexible Asymmetric Supercapacitor

Herein, we are reporting biomediated synthesis of MnO2 nanospheres thin film via facile Rotational Chemical Bath Deposition, wherein, the extract acquired by dousing Bengal gram beans (Cicer arietinum L.) in water, undeniably considered as kitchen squander is utilized as a medium for the reaction. The golden‐colored extract used as a medium contains pectin which acts as a size controlling and stabilizing agent and results in a uniform MnO2nanosphere deposition onto the substrate. Furthermore, for better comparison, the MnO2 was also synthesized without using extract. The Bio‐MnO2 thin film shows excellent results when compared with MnO2synthesized without extract. Additionally, a flexible Bio‐MnO2//Fe2O3‐based asymmetric supercapacitor (ASC) device was fabricated. The ASC exhibited a specific capacitance of 123.5 F g−1 at 5 mA cm−2current density at a potential window of 1.8 V. The device demonstrated high energy and power density with good cyclic life maintained up to 2000 cycles. A green and binder‐free approach using the R‐CBD method was used to synthesize Bio‐MnO2/FSSM thin film as the positive electrode, and Fe2O3/FSSM using SILAR approach as the negative electrode in fabricating ASC device for investigating its electrochemical performance for supercapacitor application.