Unleashing the ultrasonic frequency as a preparative parameter in tailoring the surface morphology and hence charge storage in Co3O4:MnO2@CoMnO3 composite flexible electrodes for supercapacitors

Abstract

In this study, we investigated the influence of ultrasonic frequency during ultrasound-assisted chemical bath deposition (UCBD) on the surface morphology and electrochemical performance of Co₃O₄:MnO₂@CoMnO₃ composite flexible electrodes for supercapacitor applications. By systematically varying the ultrasonic frequency (1.0–2.5 MHz), a significant modulation in surface architecture from dispersed nanoflakes to densely packed marigold-like structures was achieved. Field emission scanning electron microscopy (FESEM) and contact angle analysis confirmed improved surface ordering and wettability with increasing frequency. Electrochemical analyses demonstrated that electrodes fabricated at 2.5 MHz (F4) exhibited the highest specific capacitance (SC) of 722.27 Fg⁻¹ at 2 mVs⁻¹, attributable to enhanced electroactive surface area and reduced ion diffusion resistance. The symmetric supercapacitor device (SSD) assembled using these electrodes achieved SC of 840.35 Fg⁻¹, alongside excellent cycling stability, retaining 90.49% of its initial capacitance after 3000 cycles. These results highlight the efficacy of ultrasonic modulation in tailoring nanostructured electrode surfaces for next-generation energy storage devices.