Abstract
In this study, the synthesis of porous activated carbon nanostructures from peanut (Arachis hypogea) shell waste (PSW) was described using different porosity enhancing agents (PEA) at various mass concentrations via a two-step process. The textural properties obtained were depicted with relatively high specific surface area values of 1457 m2 g−1, 1625 m2 g−1 and 2547 m2 g−1 for KHCO3, K2CO3 and KOH respectively at a mass concentration of 1 to 4 which were complemented by the presence of a blend of micropores, mesopores and macropores. The structural analyses confirmed the successful transformation of the carbon-containing waste into an amorphous and disordered carbonaceous material. The electrochemical performance of the material electrodes was tested in a 2.5 M KNO3 aqueous electrolyte depicted its ability to operate reversibly in both negative and positive potential ranges of 0.90 V. The activated carbon obtained from the carbonized CPSW:PEA with a mass ratio of 1:4 yielded the best electrode performance for all featured PEAs. The porous carbons obtained using KOH activation displayed a higher specific capacitance and the lower equivalent series resistance as compared to others. The remarkable performance further corroborated the findings linked to the textural and structural properties of the material. The assembled device operated in a neutral electrolyte (2.5 M KNO3) at a cell potential of 1.80 V, yielded a ca. 224.3 F g−1 specific capacitance at a specific current of 1 A g−1 with a corresponding specific energy of 25.2 Wh kg−1 and 0.9 kW kg−1 of specific power. This device energy was retained at 17.7 Wh kg−1 when the specific current was quadrupled signifying an excellent supercapacitive retention with a corresponding specific power of 3.6 kW kg−1. These results suggested that peanut shell waste derived activated carbons are promising candidates for high-performance supercapacitors.
Highlights
The global demand for energy increases exponentially due to the new development and skyrocketing consumption of electronic gadgets such as mobile phones, laptops, and hybrid electric vehicles[1]
The adsorption isotherms for all the APSW-Yx exhibit a hybrid of type I and IV isotherms with a H4 hysteresis loop according to the IUPAC
An hysteresis loop between the adsorption and desorption branches indicates the presence of mesoporous at a medium pressure, while a little adsorption increase was observed relating to the existence of macropores at high pressure (P/P0 > 0.9)[37,38]
Summary
The global demand for energy increases exponentially due to the new development and skyrocketing consumption of electronic gadgets such as mobile phones, laptops, and hybrid electric vehicles[1]. SCs have attracted significant attention due to their long cycle life, stability, low maintenance and efficiency[5,6] According to their charge storage mechanism, two types of SCs can be classified namely electrical double layer capacitors (EDLCs) and faradic capacitors (FCs). The porosity enhancing agents (PEAs) play an important role in the activation process by creating a porous network, which aids the development of a high specific surface area (SSA). This can contribute to the charge storing ability and facilitate easy access of the electrolytes ions into the pores of the AC electrode materials. The KOH-activated raw material showed a higher SSA of 1721 m2 g−1 and total pore volume of 0.90 cm[3] g−1 as compared to the one activated with ZnCl2 (1210 m2 g−1 and 0.57 cm[3] g–1, respectively)
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