Construction of aqueous‐based symmetric supercapacitor with high energy from wood-based self-supporting carbon by coupling CO2 activation and redox electrolyte

Finding the delicate balance between energy storage/conversion and environmental protection is a pressing concern. This study focuses on addressing this issue by utilizing poplar-based self-supporting carbons. These carbons were prepared through chemical composition decomposition, with the hierarchical porous structures meticulously controlled using a multi-stage carbonization and green CO2 activation process. The resulting carbon material possesses a well-defined pore size structure, exhibiting good hydrophilicity, conductivity, and stable mechanical strength. And it demonstrates excellent electrochemical properties across a range of acidic, alkaline, and neutral electrolyte environments. In the single-electrode electrochemical system, the addition of a redox electrolyte yielded an outstanding specific capacitance value of 842.5 F·g–1 at 0.5 A·g–1. Moving forward, in the assembled symmetrical super capacitor, the synergistic effect of the self-supporting/hierarchical structures from the carbon electrode and the pseudocapacitance effect from the redox electrolyte enhanced the electrostatic adsorption on the carbon electrode surface. Consequently, the specific capacitance value reached 66.3 F·g–1 at 0.125 A·g–1. Moreover, the system maintained a high energy density of 23.6 Wh kg–1 at a power density of 100 W kg–1 under water system conditions. The specific self-supporting biomass-based carbon not only enables the construction of symmetrical electrodes without the need for additional additives or subsequent processing but also possesses a high energy density through a simple process under water system conditions. These materials strike an achievable balance between environmental concerns and energy demands. [Display omitted] •Support carbon aqueous‐based symmetric supercapacitors were constructed from poplar-based biomass.•The interface and pore structures of carbon were effectively controlled by the green physical activation-redox electrolyte.•The energy density was improved by controlling the interface and pore structures.