Abstract
Owing to their low cost, good performance, and high lifetime stability, activated carbons (ACs) with a large surface area rank among the most popular materials deployed in commercially available electrochemical double-layer (EDLC) capacitors. Here, we report a simple two-step synthetic procedure for the preparation of activated carbon from natural flax. Such ACs possess a very high specific surface area (1649 m2 g–1) accompanied by a microporous structure with the size of pores below 2 nm. These features are behind the extraordinary electrochemical performance of flax-derived ACs in terms of their high values of specific capacitance (500 F g–1 at a current density of 0.25 A g–1 in the three-electrode setup and 189 F g–1 at a current density of 0.5 A g–1 in two-electrode setup.), high-rate stability, and outstanding lifetime capability (85% retention after 150,000 charging/discharging cycles recorded at the high current density of 5 A g–1). These findings demonstrate that flax-based ACs have more than competitive potential compared to standard and commercially available activated carbons.
Highlights
Supercapacitors have been attracting tremendous interest for more than fifty years and are considered an excellent counterpart to batteries for energy storage applications [1].They can be sorted into two basic classes, based on the charge storage mechanism: electrochemical double-layer (EDLC) or faradic capacitors [2]
Such an AC material exhibits a very high specific surface area (SSA) (1649 m2 g–1 ) accompanied by a microporous structure with the size of pores below 2 nm. All of these facts result in extraordinary electrochemical performance in terms of high values of specific capacitance (500 F g–1 at a current density of 0.25 A g–1 in a three-electrode setup and 189 F g–1 at the current density of 0.5 A g–1 in a two-electrode setup), high-rate stability, and outstanding lifetime capability (85% retention after 150,000 charging/discharging cycles recorded at a high current density of 5 A g–1 ). These findings clearly show that a flax-based carbon derivative can be a sustainable source of AC from an abundant plant, which has more than competitive potential in comparison to standard and commercially available activated carbons
The flax hydrochar (24 g) was rinsed with distilled water and dried at 105 ◦ C for 8 h. This step was followed by the biochar activation process carried out as follows: 24 g of hydrochar was mixed with 72 g of KOH, and after complete homogenization, placed in a stainless steel reactor equipped with a corundum crucible
Summary
Supercapacitors have been attracting tremendous interest for more than fifty years and are considered an excellent counterpart to batteries for energy storage applications [1]. They can be sorted into two basic classes, based on the charge storage mechanism: electrochemical double-layer (EDLC) or faradic (pseudo) capacitors [2]. Due to the nature of the material, the EDLC-based system exhibits significantly higher lifetime stability than the pseudo-capacitors. This aspect together with the fast charging capabilities and low maintenance costs make EDCL capacitors very suitable for practical applications [11].
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