Porosity-Engineered CNT-MoS₂ Hybrid Nanostructures for Bipolar Supercapacitor Applications

Bipolar supercapacitors that can store many fold higher capacitance in negative voltage compared to positive voltage are of great importance if they can be engineered for practical applications. The electrode material encompassing high surface area, better electrochemical stability, high conductivity, moderate distribution of pore size, and their interaction with suitable electrolytes is imperative to enable bipolar supercapacitor performance. Apropos of the aforementioned aspects, the intent of this work is to ascertain the effect of ionic properties of different electrolytes on the electrochemical properties and performance of a porous CNT-MoS₂ hybrid microstructure toward bipolar supercapacitor applications. The electrochemical assessment reveals that the CNT-MoS₂ hybrid electrode exhibited a two- to threefold higher areal capacitance value of 122.3 mF cm^-2 at 100 μA cm^-2 in 1 M aqueous Na₂SO₄ and 42.13 mF cm^-2 at 0.30 mA cm^-2 in PVA-Na₂SO₄ gel electrolyte in the negative potential window in comparison to the positive potential window. The CNT-MoS₂ hybrid demonstrates a splendid Coulombic efficiency of ∼102.5% and outstanding stability with capacitance retention showing a change from 100% to ∼180% over 7000 repeated charging-discharging cycles.