Mn3O4 nanoparticles grown on surface activated graphite paper for aqueous asymmetric supercapacitors

Highlights: • Mn₃O₄ nanoparticles are grown on surface activated graphite paper via template free hydrothermal method. • The nanoparticles exhibited a specific capacitance of 471 F g⁻¹ at a current density of 1 mA cm⁻² in 1 M Na₂SO₄. • A class of Mn₃O₄||AC 1.6 V asymmetric cell was fabricated. • The asymmetric cell fabricated delivered a maximum specific energy of 47 Wh kg⁻¹ at a power density of 202.5 W kg⁻¹. • The asymmetric cell retained 81.6% capacitance even after 5000 cycles. Mn₃O₄ nanoparticles were anchored on the surface of oxidised graphite paper via template-free hydrothermal method. Synthesized samples were characterized using different techniques such as X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Photoelectron Spectroscopy (XPS). Electrochemical capacitor behaviour was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The binder free material was found to exhibit a specific capacitance of 471 F g⁻¹ at a current density of 1 mA cm⁻² in 1 M Na₂SO₄. Conductive additive free, Mn₃O₄ anchored electrode was used as positive electrode in the asymmetric cell fabrication; the asymmetric cell was tested at a potential window of 1.6 V and its performance characteristics were evaluated. The asymmetric cell delivered a maximum specific energy of 47 Wh kg⁻¹ at a power density of 202.5 W kg⁻¹ which evidenced the superior performance of the synthesized electrode material. Here in the present work, the surface oxidised graphite paper was used as an excellent current collector and active sites for anchoring Mn₃O₄ due to its desirable properties.