Effect of Aqueous Electrolytes on the Electrochemical Performance of MoO ₃ Nanobelts

Achieving optimal supercapacitor performance requires a customized combination of electrode material and electrolyte. This study examines the electrochemical behavior of hydrothermally synthesized molybdenum trioxide (MoO 3 ) nanobelts in 1 M aqueous solutions of Na 2 SO 4 , KOH, and H 2 SO 4 . The results demonstrate that the highest specific capacitance of 227.9 F/g was achieved in 1 M H 2 SO 4 at a scan rate of 5 mV/s. This superior performance is attributed to the high mobility and small ionic and hydration radii of the H + ions compared to the Na + and K + ions in the other electrolytes. Additionally, Electrochemical Impedance Spectroscopy (EIS) data revealed lower solution and charge transfer resistance for the MoO 3 nanobelt electrode in the acidic electrolyte, which promotes faster charge transfer. Despite its superior initial performance, the long‐term stability of the studied material was better in neutral Na 2 SO 4 and alkaline KOH electrolytes, showing capacitance retention of 97% and 95%, respectively, after 5000 cycles. A fairly good stability of 88% was achieved in the acidic H 2 SO 4 solution. It suggests that the electrode deteriorated due to a combination of intricate side reactions, the degradation of adhesives, and the peeling‐induced loss of active material. This study provides an effective framework for selecting electrolytes for energy storage systems.