Self-templating synthesis strategy of oxygen-doped carbon from unique wasted pulping liquid directly as a cathode material for high-performance zinc ion hybrid capacitors.

Affinity and storage capacity for zinc ions of the electrode materials are crucial factors on the properties of zinc ion hybrid capacitors (ZHICs). Wasted pulping liquor with abundant carbohydrates, lignin and inorganic matter served as a unique precursor to produce embedded oxygen-doped hierarchical porous carbon directly through a one-step carbonization process in this investigation. In carbonization process, lignin can serve effectively as the carbon framework, carbohydrates not only act as sacrificial templates but also offer a plentiful oxygen source which can increase the affinity for Zn ²⁺ , and sodium-containing inorganic substances plays a role as hard templates to optimize the pore structure. The resulting porous carbon under carbonization temperature of 800 °C shows a high specifical area of 2186 m ² g ^-1 with oxygen content of 4.8 %, which can reduce the adsorption energy of Zn ²⁺ from -0.16 eV to -0.32 eV through electrochemical techniques and density functional theory (DFT) calculations, the incorporation of oxygen was demonstrated to enhance the adsorption and desorption kinetics of Zn ²⁺ , suggesting a bright future for application in the domain of energy storage. The resulting ZIHC assembly showcases a notable energy density of 84.6 Wh kg ^-1 at a power density of 359 W kg ^-1 . Remarkably, even after 10,000 charge and discharge cycles, it exhibits exceptional cycle stability with retaining 86.56 % of its capacity. Consequently, this approach provides fresh insights for exploring the facile and commercial fabrication of biomass-derived cathodes for ZIHCs, thereby propelling the progress of eco-friendly energy storage devices.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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