Surfactant-assisted morphology modification of nanostructured MnMoO4 for high-performance asymmetric supercapacitors

Abstract

Supercapacitors are regarded as promising electrochemical energy storage solutions due to their multiple advantages. In this study, we report simple hydrothermal synthesis of nanostructured MnMoO₄ (MMO) using CTAB and PVA as structure-directing agents, which is then employed as an electrode material in high-performance asymmetric supercapacitors. This resulted in the formation of morphologies analogous to nanoflakes (for CTAB; MMO-C), nanosheets (for PVA; MMO-P), and nanobundles (without a surfactant; MMO). MMO-C has a nanoflake-like structure with a large surface area, and an increasing number of electroactive surface sites and contact areas at the electrode–electrolyte interface. This results in a higher specific capacitance than other electrodes, measuring 919.6 F g⁻¹ and 505 F g⁻¹ at 1 A g⁻¹ and 10 A g⁻¹, respectively. It also exhibits extended cycling performance, with 94.1% retention after 10 000 cycles. The fabricated MMO-C//activated carbon (AC) asymmetric supercapacitor (ASC) device achieved a high specific capacitance of 111.9 F g⁻¹ at 1 A g⁻¹ in an operational potential window of 0–1.5 V. The ASC also has a high specific energy of 39.45 W h kg⁻¹ at a specific power of 837.66 W kg⁻¹ while retaining 90.3% of its initial capacitance after 10 000 cycles. A red LED was also turned on for 120 seconds when two ASCs were connected in series.