Pore regulation and surface modification collaboratively enhance biomass porous carbon anchoring azure A for stable supercapacitor electrode

Biomass derived porous carbon shows promising application potential in energy storage, however, the electric double layer charge storage mechanism of carbon material triggers low capacitance performance. The combination of porous carbon with redox-active molecules is effective measure to break through its application bottleneck. In this work, pore structure and surface charge state of wheat straw derived carbon (WS) were reasonably regulated by KOH activation and sodium dodecyl sulfate (SDS) modification, respectively. Moreover, microporous structure and abundant negatively charged groups in SDS modified porous carbon (SWS) enhance the anchoring of redox active molecule azure A (AA) through micropore confinement and electrostatic interaction. The leakage of AA molecule from porous carbon is suppressed and AA@SWS composite exhibits good electrochemical stability. AA@SWS shows high specific capacitance (557.9 F g-1 at 1 A g-1) and durable cycle stability (capacitance retention of 92.4% after 12,000 charge-discharge cycles). Ex-situ XPS reveals the reversible change of C--N active site during charge-discharge process. Density functional theory calculations show that AA@SWS system has a lower adsorption energy than AA@WS system. Symmetric supercapacitor with AA@SWS as electrode delivers high energy density (32.1 Wh kg- 1) and power density (6500.0 W kg- 1), and the capacitance remains 88.9% after 10,000 charge-discharge cycles. This work provides new insights for constructing high-performance and stable carbon-organic composite electrode.