N/O co-doped edamame shell derived porous carbon materials for high-performance supercapacitors†

Abstract

Supercapacitors, an innovative energy storage technology, combine the strengths of batteries and capacitors, enabling diverse applications in sectors such as communications, transportation, and aerospace. Porous carbon materials derived from biomass have excellent electrical conductivity, customizable dimensions, high surface area, and robust electrochemical stability, rendering them ideal candidates for supercapacitor electrodes. This research utilized edamame shells as the carbon precursor and KOH as the activating agent to synthesize a series of N/O co-doped porous carbons (ESC-x-800) through a combined pre-carbonization and activation process. This study thoroughly investigated the effect of KOH addition on the morphology, structure, and electrochemical performance of the materials. The result showed that the ESC-3-800 stood out as the top performer, distinguished by its unique self-doping characteristic with N and O atoms and a unique hierarchical porous structure. The ESC-3-800 boasted an impressive specific surface area of 3188.98 m² g⁻¹, coupled with a substantial pore volume of 1.86 cm³ g⁻¹. When evaluated in a three-electrode system, ESC-3-800 demonstrated a remarkable specific capacitance of 301 F g⁻¹, and a capacitance retention rate of 73.1% at a high current density of 20 A g⁻¹. In a two-electrode setup, the ESC-3-800 achieved a notable high energy density of 37.6 W h kg⁻¹ (at a power density of 200 W kg⁻¹) in the 1 M Na₂SO₄ electrolyte. Remarkably, after enduring 12 000 charge–discharge cycles in 6 M KOH, it maintained an impressive 96.68% of its initial capacity (8 A g⁻¹), demonstrating exceptional long-term stability and durability. The straightforward preparation method and outstanding performance of the edamame shell-derived N/O co-doped porous carbon underscore its immense potential for practical applications in supercapacitors.