Unveiling the future of Ultrasound Chemical Bath Deposition method for flexible supercapacitive electrodes : Impact of cationic precursors on MnO2 flexible electrodes – a case study

Abstract MnO2 flexible electrodes (FEs) were synthesized by novel ultrasound chemical bath deposition (UCBD) using aqueous solutions of three different manganese (II) cationic precursors viz. manganese acetate, manganese chloride, and manganese nitrate. 1M aqueous NaOH solution was used as the oxidizer for each precursor. Under optimized preparative conditions, uniform MnO2 films grew on the substrates to form the FEs. XRD analysis confirmed the formation of crystalline MnO2, further corroborated by EDX. FESEM imaging revealed a transition in surface morphology from mud-like structures with manganese acetate to randomly arranged nanoflakes with manganese nitrate. Surface modification was confirmed by contact angle measurements. Cyclic voltammetry showed the specific capacitance (SC) varied with the Mn2+ cation source. Galvanostatic charge-discharge further confirmed this trend. The highest SC of 408.50 Fg-1 was exhibited by electrodes prepared with Mn(NO3)2.6H2O with 90.61 % retention in SC even after 2000 CV cycles.