Selective phase control and enhanced electrochemical performance of rGO-MnO<inf>2</inf> nanocomposites for supercapacitor electrodes via solution plasma process: A greener alternative to hydrothermal process

Abstract

This study introduces a greener and scalable solution plasma process (SPP) for synthesizing reduced graphene oxide–manganese dioxide (rGO-MnO2) nanocomposites with precise phase control, offering a novel alternative to conventional hydrothermal processes (HTP). Unlike HTP, which typically produces mixed-phase manganese oxides, SPP enables the selective deposition of pure δ-MnO2 onto rGO surfaces using potassium permanganate (KMnO4) in an aqueous system. Additionally, rGO is prepared without toxic reductants, enhancing the sustainability of the process. Electrochemical evaluations reveal that SPP-derived rGO-MnO2 (SPP-rGOM) achieves a specific capacitance of 89.2 F g−1, comparable to HTP-rGOM (92.5 F g−1), while demonstrating significantly superior cycling stability—retaining 76.8 % of its capacitance after prolonged cycling compared to 54.0 % for HTP-rGOM at 30 mV s−1. These findings establish SPP as an innovative, environmentally friendly approach for the scalable production of durable, high-performance electrode materials for energy storage applications.