In Situ O and N Self-Doped Fruit Waste-Derived Microporous Activated Carbon for All-Solid-State Supercapacitors

Activated carbon, known for its simple preparation, cost-effectiveness, physicochemical stability, and wide applicability, has garnered significant attention. As a primary application, supercapacitors focus on developing porous activated carbon materials with high surface area, high porosity, and low cost. Herein, a straightforward and efficient two-step process of high-temperature carbonization and activation was introduced to successfully synthesize Rosa roxburghii Tratt fruit waste-derived porous activated carbon (RFAC) with in situ N and O self-doping. The optimized RFAC-6 possesses an exceptional specific surface area (3952.9 m(2) g(-1)), with micropores constituting up to 99% and a rich presence of heteroatom functional groups. The RFAC-6 electrode demonstrates remarkable specific capacitance (370 F g(-1) at 0.5 A g(-1)), excellent rate capability (69% at 20 A g(-1)), and outstanding cyclic stability (95% capacity retention after 5000 cycles). To assess the practicality of RFAC-6, symmetric supercapacitors (SSCs) were assembled by using aqueous KOH, ionic liquid ([BMIM]BF4), and solid-state PVA/KOH electrolytes, all exhibiting superior electrochemical performance. Notably, the KOH SSC achieves a high specific capacitance of 91 F g(-1) at 0.25 A g(-1), the [BMIM]BF4 SSC reaches an ultrahigh energy density of 56.6 W h kg(-1) at a power density of 375 W kg(-1), and the PVA/KOH SSC maintained 92% of its initial capacity even after 10,000 charge-discharge cycles. The activated carbon material prepared from R. roxburghii Tratt fruit waste exhibits exceptional electrochemical performance in various electrolytes, demonstrating significant potential in the energy storage field.