Energy Storage Performance of Environmentally Friendly Lotus Petiole–Porous Carbon Composites

Waste management is essential to achieve sustainable development and protect the environment. Herein, a strategy was tested to utilize large volumes of lotus petiole waste. In this work, a composite supercapacitor electrode of lotus petiole with a porous structure and MoO2 with an ice flower structure was fabricated via an in situ hydrothermal growth method. The prepared PC-50 lotus petiole–porous carbon material exhibited a unique hierarchical porous structure and a high specific surface area (1887 m2 g–1). The composite electrode exhibits high reversible capacity (515.10 mAh g–1 at 2 A g–1) in the three-electrode system. The maximum gravimetric energy density reached 30.10 W h kg–1 at a power density of 387 W kg–1, and a favorable energy density of 20.19 W h kg–1 was retained even at a high power density of 3.69 kW kg–1 in the symmetric device. Moreover, the symmetric device shows superior cycling stability (91.60% capacity retention in 2000 cycles). Electrochemical impedance spectroscopy was used to study the electrochemical interface characteristics and verify the electrochemical performance of the composite electrodes. The research results provide guidance for the design of high-performance metal oxide–biomass carbon composites and the comprehensive utilization of waste biomass.