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

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.