| Summary: | Biomass-waste activated carbon/molybdenum oxide/molybdenum carbide ternary composites are prepared using a facile in-situ pyrolysis process in argon ambient with varying mass ratios of ammonium molybdate tetrahydrate to porous peanut shell activated carbon (PAC). The formation of MoO<sub>2</sub> and Mo<sub>2</sub>C nanostructures embedded in the porous carbon framework is confirmed by extensive structural characterization and elemental mapping analysis. The best composite when used as electrodes in a symmetric supercapacitor (PAC/MoO<sub>2</sub>/Mo<sub>2</sub>C-1//PAC/MoO<sub>2</sub>/Mo<sub>2</sub>C-1) exhibited a good cell capacitance of 115 F g<sup>−1</sup> with an associated high specific energy of 51.8 W h kg<sup>−1</sup>, as well as a specific power of 0.9 kW kg<sup>−1</sup> at a cell voltage of 1.8 V at 1 A g<sup>−1</sup>. Increasing the specific current to 20 A g<sup>−1</sup> still showcased a device capable of delivering up to 30 W h kg<sup>−1</sup> specific energy and 18 kW kg<sup>−1</sup> of specific power. Additionally, with a great cycling stability, a 99.8% coulombic efficiency and capacitance retention of ~83% were recorded for over 25,000 galvanostatic charge-discharge cycles at 10 A g<sup>−1</sup>. The voltage holding test after a 160 h floating time resulted in increase of the specific capacitance from 74.7 to 90 F g<sup>−1</sup> at 10 A g<sup>−1</sup> for this storage device. The remarkable electrochemical performance is based on the synergistic effect of metal oxide/metal carbide (MoO<sub>2</sub>/Mo<sub>2</sub>C) with the interconnected porous carbon. The PAC/MoO<sub>2</sub>/Mo<sub>2</sub>C ternary composites highlight promising Mo-based electrode materials suitable for high-performance energy storage. Explicitly, this work also demonstrates a simple and sustainable approach to enhance the electrochemical performance of porous carbon materials.
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