Spinel-Functionalized Bamboo-Derived Hierarchical Carbon: Dual Activation Strategy for Synergistic Double-Layer/Pseudocapacitance Energy Conversion

Luanxing JinZhi Cheng^*Shuhan Zhang^*

• China Three Gorges University, Hubei, China

In response to the dual bottlenecks of low energy density in carbon materials and poor cycling stability of metal oxides in supercapacitors, this study proposes a biomimetic hierarchical pore engineering strategy. Using bamboo-based biochar as a precursor, a hierarchical structure consisting of "ultra-micropores (0.55 nm, accounting for 42%) -mesopores (1.32 nm, accounting for 38%)" is constructed through coupled CO₂ physical activation (PHAC) and KOH chemical activation (CHAC), achieving a micropore/mesopore volume ratio of 0.45. Additionally, a supercritical-assisted impregnation method is employed to selectively anchor 5 wt% MnCo₂O₄ spinel on the surface of activated carbon. XPS characterization confirms the formation of strong interfacial C-O-Mn/Co bonds (12.4%) and mixed valence states of Mn³⁺/Mn²⁺ (62:38), which synergistically optimizes charge transfer efficiency. This electrode achieves a high specific capacity of 1258 F/g at a current density of 1 A/g (a 44% increase compared to pure AC), with a capacity retention of 80% (1004 F/g) at a high rate of 10 A/g, and a remarkable energy density of 59.18 Wh/kg at a power density of 8.42 kW/kg. For the first time, the dual activation strategy eliminates the negative pore volume phenomenon and reveals its synergistic mechanism in accelerating H⁺ transport (with a diffusion rate increase of 37%) and buffering load fluctuations through the hierarchical pore channels in PEMFC, providing a new paradigm for high-performance energy storage devices.