Dual regulation strategy to synthesize rich oxygen-vacancy S-doped FeCo2O4 nanosheets as high-performance supercapacitor electrodes

Abstract

Cobalt-based spinel oxides, specifically MCo₂O₄ (M = Ni, Mn, Cu, Fe, etc.), have attracted considerable interest due to their promising applications in energy storage technologies. Herein, a dual regulation strategy was developed for the synthesis of S-doped FeCo₂O₄ nanosheets enriched with oxygen vacancies (S-FeCo₂O_4−x), which serve as high-performance electrodes for supercapacitors. By utilizing electrodeposition, precise control over the nanosheet morphology was achieved while thiourea was introduced to facilitate the incorporation of sulfur, significantly enhancing the formation of oxygen vacancies. The electrochemical performance was assessed in a 3 M KOH electrolyte, demonstrating a specific capacitance of 993 F g⁻¹ at 1 A g⁻¹, exceptional cycling stability (98.8% retention after 5000 cycles), and superior rate capability. Additionally, an asymmetric supercapacitor (ASC) using S-FeCo₂O_4−x and activated carbon (AC) exhibited a maximum specific capacitance of 221 F g⁻¹ at 1 A g⁻¹ with excellent cycling stability (92.7% retention after 5000 cycles). This study elucidates the potential of S-FeCo₂O_4−x nanosheets for advancing energy storage technologies and highlights the effectiveness of defect engineering in enhancing electrode performance.