Synthesis of Ultrathin MnO2 Nanowire-Intercalated 2D-MXenes for High-Performance Hybrid Supercapacitors

Recently, the MXene itself and its composites with various metal oxides have shown excellent electrochemical performance due to the presence of multiple oxidation states. However, the restacking of MXene layers and poor electrical conductivity of metal oxides are major bottlenecks in their effective electrochemical transport, when they are applied individually. Herein, we report a novel manganese oxide/MXene (MnO2/MXene) composite material to overcome these critical issues. Sub-50 nm-thick MnO2 nanowires (NWRs) were introduced inside the MXene to effectively stop the restacking as well as to increase the surface area of the supercapacitor (SC) electrode material. The special control on the thickness of NWRs is not only providing an opportunity to adjust them inside the MXene layers but also giving a high surface area. Electrochemical studies suggested that the MnO2/MXene composite behaves as an excellent electrode material for hybrid SCs, as compared to individual MXene and MnO2. Maximum specific capacitance (C-sp) of MXene, MnO2 NWRs, and MnO2/MXene composite was observed to be about 527.8, 337.5, and 611.5 F/g, respectively. The calculated specific capacity of the MnO2/MXene composite was about 489.5 C/g at 1 A/g, which shows better performance as an electrode material for energy storage devices. The synthesized electrode material demonstrated excellent capacitance retention of about 96% up to 1000 cycles.

Automated summary

The novel manganese oxide/MXene composite material overcomes the issues of MXene layer restacking and poor electrical conductivity of metal oxides, increasing the surface area of the electrode material and exhibiting excellent electrochemical performance.