Activated carbon nanofibers (ACFs) with high specific surface area, excellent conductivity, and narrow pore‐size distribution, are regarded as a promising electrode material for high‐performance supercapacitors (SCs). Herein, a facile route to synthesize large‐scale amorphous CF (a‐CF) using catalytic pyrolysis of acetylene (C2H2) at 260 °C over copper catalysts is reported. The conversion rate of acetylene into a‐CF is estimated as high as 72.05 wt%. Subsequently, the as‐prepared a‐CF is transformed into ACFs by potassium hydroxide (KOH) at 800 °C with high specific surface area and porous structures. Moreover, nitrogen‐doped ACFs are conducted in the activation step through a physical mixing of a‐CF/KOH/melamine with various ratios. For SCs, the as‐prepared N‐ACFs display excellent specific capacitance and cycle stability. In the three‐electrode system, the N‐ACF (CF‐03) demonstrates a specific capacitance value of 227 F g−1 at 0.5 A g−1, and shows a 94% capacitance retention after a long cycle (10 000 cycles) at 2 A g−1. Moreover, the CF‐03‐based two‐electrode SC demonstrates a high energy density of 14.30 Wh kg−1 and a high power density of 79.88 W kg−1 in 1 m Na2SO4 electrolyte. Herein, a simple and promising way to prepare large‐scale a‐CF, ACF, and N‐doped ACFs is demonstrated.
Although highly porous carbon electrode materials from biomass wastes for high-performance electric double-layer capacitors (EDLCs) have attracted great attention recently, the fast charge−discharge performance under ultrahigh current density (100 A g −1 ) still remains a challenge. Herein, we develop a promising route to massively prepare honeycomb-like activated carbon (AC) with hierarchical porous features from spent lotus stems (SLSs) exhibiting an ultrahigh specific surface area of 4190 m 2 g −1 . The preparation process of the SLSAC samples includes carbonization at 400 °C in argon (denoted as c-SLS) and followed a KOH chemical activation using various KOH/c-SLS mass ratios at 800 °C for 1 h. The SLSAC-5-based electrode (KOH/c-SLS = 5/1) displays a good gravimetric capacitance of 330 F g −1 at 0.5 A g −1 with a superior high-rate capacitance of 243 F g −1 at 100 A g −1 and presents remarkable cycling stability with a capacitance retention near 100% over 10,000 cycles at 2 A g −1 using 6 M KOH aqueous electrolyte. Additionally, the SLSAC-5-based sample delivers an energy density of 18.6 W h kg −1 at 199.2 W kg −1 with 1 M Na 2 SO 4 electrolyte. Herein, we reveal a simple, promising route to massively generate SLSAC-based samples and investigate prominent electrochemical properties in ultra-fast charge−discharge EDLCs.
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