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

Abstract Herein, we are reporting biomediated synthesis of MnO 2 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 MnO 2 nanosphere deposition onto the substrate. Furthermore, for better comparison, the MnO 2 was also synthesized without using extract. The Bio‐MnO 2 thin film shows excellent results when compared with MnO 2 synthesized without extract. Additionally, a flexible Bio‐MnO 2 //Fe 2 O 3 ‐based asymmetric supercapacitor (ASC) device was fabricated. The ASC exhibited a specific capacitance of 123.5 F g −1 at 5 mA cm −2 current 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.