Rosette-shaped Co2Mn3O8 integrated with nanoflower-like Mn–Co LDH anchored on rGO sheets: a bifunctional electrode for advanced supercapacitors and oxygen evolution reaction (OER)

Abstract

Mn–Co layered double hydroxide (LDH) is a promising electrode material for supercapacitor and oxygen evolution reaction (OER) applications due to its unique layered structure with Mn and Co active sites. However, its full potential for supercapacitor and OER applications is underutilized due to its low conductivity and limited availability of active sites. The challenges related to the super capacitive and OER properties of Mn–Co LDH are overcome by combining it with highly redox-active Co₂Mn₃O₈ and highly conductive rGO to form the Mn–Co LDH/rGO/Co₂Mn₃O₈ composite. The hierarchical rosette- and nanoflower-like Mn–Co LDH/rGO/Co₂Mn₃O₈ composite is prepared using a hydrothermal method followed by calcination. Characterization using FESEM, XRD, XPS, and Raman spectroscopy reveals a unique morphology that enhances conductivity and results in improved performance for supercapacitor and OER applications. As a result, the Mn–Co LDH/rGO/Co₂Mn₃O₈ composite demonstrates a high specific capacitance of 2500 F g⁻¹ at 1 A g⁻¹ in a 3 M KOH electrolyte. Furthermore, the asymmetric supercapacitor (ASC) device employing Mn–Co LDH/rGO/Co₂Mn₃O₈ delivers an energy density of 32 Wh kg⁻¹ at a power density of 600 W kg⁻¹. The zinc-ion supercapacitor based on Mn–Co LDH/rGO/Co₂Mn₃O₈ achieves an impressive energy density of 100 Wh kg⁻¹ at a power density of 780 W kg⁻¹. Additionally, Mn–Co LDH/rGO/Co₂Mn₃O₈ performs well for the OER, exhibiting a low overpotential of 218 mV (at 10 mA cm⁻²) and a small Tafel slope of 56.03 mV dec⁻¹ in 0.1 M KOH. This study opens promising prospects for the dual utilization of Mn–Co LDH/rGO/Co₂Mn₃O₈ in supercapacitor and OER applications.