Supercapacitive vertical graphene nanosheets in aqueous electrolytes

Vertical graphene nanosheets (VGN) is a potential material for high-performance supercapacitors due to its high surface area, open interconnected network and excellent electrical conductivity. Selection of proper aqueous electrolyte is crucial for its utilization as supercapacitor electrode. The present study reports supercapacitive performance of vertical graphene nanosheets in neutral (Na₂SO₄), alkaline (KOH), and acidic (H₂SO₄) aqueous electrolytes. Factors like ionic mobility and electrolyte wettability are found to influence supercapacitor performance. The highest capacitance observed for VGN in KOH (197 μF/cm²) is attributed to the higher wettability, whereas VGN /H₂SO₄ system with specific areal capacitance of 188 μF/cm² is found to have highest capacitance retention (96.8%), shortest relaxation time (50 ms), low charge transfer resistance (72 Ω cm²) and minimal change in graphitic structure. The later observation is correlated to cationic mobility. Detailed supercapacitive investigation is presented including equivalent circuit simulation for deduction of electrode/electrolyte interface behavior.