Effect of surfactant on high capacitance of galvanostatically deposited MnO2

Manganese dioxide has been galvanostatically deposited on stainless-steel substrate from an aqueous acidic solution of manganese sulphate (1 M) in presence of a surface active agent (surfactant), namely, sodium lauryl sulphate (SLS), for supercapacitor applications. The deposits have been developed under different conditions of SLS and their specific capacitance is measured by cyclic voltammetry (CV) and also by galvanostatic charge/discharge cycle. The oxide film (∼0.1 mg cm−2) anodized from the manganese solution at 2.0 mA cm−2 has shown the highest specific capacitance of 255.8 F g−1, at scan rate of 10 mV s−1. It is observed that the capacitance increased by about 40% compared to the oxide prepared in the absence of SLS. Improved specific capacitance is due to the effect of the surfactant molecules in the deposit, causing high surface area of the deposit. The deposit is found to display good cycleability, even up to 1500 cycles. The structure and surface morphology of the deposits have been studied by means of X-ray diffraction (XRD) analysis and Scanning Electron Microscopy (SEM). XRD study reveals that crystallinity of the deposit with SLS remains unchanged, both are amorphous in nature. The surface area of the deposit is found to increase considerably due to the effect of SLS, as evident by SEM study.

► Galvanostatic deposition of MnO2 on SS and study of the effect of surfactant (SLS). ► Cyclic voltammetric and charge/discharge studies done using 0.1 M Na2SO4. ► Increase of 40% of the specific capacitance of MnO2 in presence of SLS (255.8 F g−1). ► Increase in capacitance due to increase in surface area.