Effect of porosity enhancing agents on the electrochemical performance of high-energy ultracapacitor electrodes derived from peanut shell waste

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.

More Sustainable Chemical Activation Strategies for the Production of Porous Carbons

“…400 °C), [36,39] which explains the lower pore development achieved with K 2 CO 3 compared to KOH (Table 1). [40–44] Besides, as mentioned above, K 2 CO 3 is one of the products during KOH activation, so that for T >600–700 °C, reactions (1) to (4) also take place during KOH activation, yielding additional pore development. However, K 2 CO 3 has two important additional advantages over KOH.…”

“…It should be noted that the carbon yield of the process is not very high, of around 6–10 % for a KHCO 3 /precursor weight ratio of 4 : 1 (Table 1). Since this study, KHCO 3 activation has been applied to a variety of precursors, including not only biomass, [57–66] but also biochar [43,67–69] and hydrochar, [37,70–72] for use in a variety of applications, as compiled in Table 1.…”

Nitridation Temperature Effect on Carbon Vanadium Oxynitrides for a Symmetric Supercapacitor

“…Interestingly, the specific energy value after 50 h improved from 23 to 27 W h kg −1 before reaching a plateau at a value of 32 W h kg −1 , corresponding to an increase of 27% from the original value of 23 W h kg −1 . This increase in specific capacity and specific energy can be associated to the increase in accessibility of the ions to initially inaccessible redox sites which could increase the wettability and a large diffusion of ions between the electrolyte/electrode during the long floating time (100 h) [63]. The cycling stability and the floating test of the device indicated that the symmetric device showed a good long-term stability without any significant degradation.…”

Preparation of Hierarchical Porous Activated Carbon from Banana Leaves for High‐performance Supercapacitor: Effect of Type of Electrolytes on Performance

“…It might be attributed for the high viscosity of IL and high porous structure of ACNSs. The E values are high compared to other biomass‐derived carbon‐based supercapacitor electrode materials reported in the literature [8,17,21,25,49,51,54,57] . The P values are also high compared to the ACs derived from rice husk, [8] peanut shell, [21] and cauliflower [50] .…”

“…In general, the trend has been to increase capacitance by increasing surface area [18,19] . However, the electrical conductivity of the AC, its structure including the shapes and sizes, number of its pores, and the identities of the functional groups on its surface, must also be considered for achieving the best performance possible [20,21] . The arrangement and type of porosity of the AC materials limit its accumulation and mobility of ions, and thus its capacitance, specific energy and power [21–24] …”