Exploring Electrolyte-Induced Phenomena in Graphene Nanoplatelet-Based Electrodes

Graphene has a large surface area, an open interconnect structure, and superior electrical conductivity, making it a promising material for high-performance supercapacitors. The appropriate choice of aqueous electrolyte is essential for its application as an electrode in a supercapacitor. The present study explores the supercapacitive behavior of graphene nanoplatelets in aqueous electrolytes that are acidic (H₂SO₄), alkaline (NaOH), and neutral (Na₂SO₄). Among these, H₂SO₄ delivers the maximum capacitance of 292 F/g, followed by NaOH and Na₂SO₄, with specific capacitance of 276 F g⁻¹ and 240 F g⁻¹, respectively, from cyclic charge–discharge at a current density of 0.3 A g^-1. Additionally, this electrode has maximum energy density and power density of 28 Wh kg⁻¹ and 270 W kg⁻¹, and it retains 90% of its capacity over 5000 cycles in H₂SO₄ electrolytes. An in-depth examination of supercapacitance is provided, along with an equivalent circuit simulation to deduce the behavior of the electrode–electrolyte interface.