Converting Hippophae rhamnoides fruit extraction residue into porous carbons with ultra-high surface area for superior-performance supercapacitors

Scalable production of carbon materials from sustainable and renewable biomass as electrode materials in supercapacitors (SCs) has garnered considerable attention. However, the practical applications of the carbon-based SCs are still been hindered by the low energy density . Herein, hierarchical porous carbons (HPCs) with very high specific surface area and controlled porosity were synthesized by a facile method, which employed Hippophae rhamnoides fruit (HRF) extraction residue as raw materials, and KOH as the activation agent. The prepared carbon (HRF-NPC-2) exhibited a well-developed hierarchical pore structure , which gave an ultra-large specific surface area (SSA) of 2362.8 m 2  g −1 with a pore volume of 1.27 cm 3  g −1 . Electrochemical studies showed that the HRF-NPC-2 based electrode achieved an ultra-high specific capacity of 385.0 F g −1 at 1 A g −1 , and the symmetric supercapacitor in an ionic liquid electrolyte (1 M EMIMBF 4 ) achieved superior energy densities of 36.28 Wh kg −1 at 687.5 W kg −1 , and 43.82 Wh kg −1 at 1715 W kg −1 . Most importantly, the HRF-NPC-2//HRF-NPC-2 symmetric SCs can simultaneously light 88 LED lights for over 10 min, indicating great potential for practical application. The proposed simple fabrication strategy could be extended to convert other biomass waste into useful energy storage materials for supercapacitors .