N and P Co‐doped Green Waste Derived Hierarchical Porous Carbon as a Supercapacitor Electrode for Energy Storage: Electrolyte Effects

Abstract

N, P dual-doped watermelon peel-derived carbon (NPW) was prepared and found to exhibit a larger specific surface area of 1809 m 2 g À 1 and improved hierarchically interconnected pores than N-doped and P-doped carbons. The NPW electrode exhibits excellent electrochemical activity in a three-electrode setup with 1 M H 2 SO 4 , 6 M KOH, and 1 M Na 2 SO 4 electrolytes; with high specific capacitance (498.8, 397.6, and 378.6 F g À 1 at 1 A g À 1 , respectively) and an average capacitance retention of ∼ 96.9 % after 10,000 charge-discharge cycles at 10 A g À 1 . The NPW//NPW-based symmetric cell with 1 M H 2 SO 4 -PVA-electrolyte provided a high energy density of 71.84 Wh kg À 1 at 1 A g À 1 and a specific capacitance of 263.9 F g À 1 . In the neutral electrolyte, NPW showed a wider operating voltage window of up to 2.0 V with no discernible anodic current and delivered 97.11 Wh kg À 1 energy density.

Mechanochemically Assisted Microwave-Induced Plasma Synthesis of a N-Doped Graphitic Porous Carbon-Based Aqueous Symmetric Supercapacitor with Ultrahigh Volumetric Capacitance and Energy Density

“…This quick ion transport through the interconnected and uniform porous network of HP-NGC reduces its internal resistance, enabling high charge/discharge rates and hence improving the capacitance of the HP-NGC electrode. 19 However, the macropores present in the HP-NGC probably function as ion-buffering reservoirs, minimizing the diffusion distance of the electrolyte, and hence, promoting a consistent and efficient ion distribution throughout the electrode material. 18,28 The cycling performance of the developed electrodes is also carried out and shown in Figure 5g, which confirmed that the HP-NGC electrode retained 80% of its initial capacitance after 10,000 cycles with a remarkable Coulombic efficiency of 101%.…”

“…However, they seriously suffer from agglomeration during solution processing, which restricts their surface area and reaction kinetics to result in low volumetric capacitance (∼<60 F cm –3 ) and energy density . Recent studies ,− indicate that the preparation of heteroatom-doped biomass-derived carbon with adjusted pore structures could be a potential strategy to enhance the electrochemical storage performances of carbon-based SCs by improving surface wettability, , electrolyte diffusion, and pseudocapacitance (PC). ,, For instance, Liang et al have synthesized N- and sulfur (S)-codoped hierarchical porous carbon electrodes from foxtail grass seeds through a multistep method, including freeze-drying and pyrolysis at different temperatures with the addition of mixed additives like NaHCO 3 and KHCO 3 in 1:1 weight ratio to deliver a moderate volumetric capacitance of 243.4 F cm –3 at 0.5 A g –1 and an electrode energy density of 33.8 Wh L –1 in 6 M KOH having a limited potential window of 1 V. In another report, N- and oxygen (O)-codoped carbon electrodes were prepared from soybean dregs through time- and energy-consuming multistep heating, including the hydrothermal method at 100 °C for 6 h followed by conventional carbonization at 650 °C for 2 h using KOH as an activating agent. Moreover, the developed material showed an inferior volumetric capacitance of 247.6 F cm –3 and an energy density of 34.3 Wh L –1 at 0.5 A g –1 in 6 M KOH in a limited potential window of 1 V .…”

“…17 Recent studies 14,18−20 indicate that the preparation of heteroatomdoped biomass-derived carbon with adjusted pore structures could be a potential strategy to enhance the electrochemical storage performances of carbon-based SCs by improving surface wettability, 14,19 electrolyte diffusion, and pseudocapacitance (PC). 14,19,20 For instance, Liang et al 21 have synthesized N-and sulfur (S)-codoped hierarchical porous carbon electrodes from foxtail grass seeds through a multistep method, including freeze-drying and pyrolysis at different temperatures with the addition of mixed additives like NaHCO 3 and KHCO 3 in 1:1 weight ratio to deliver a moderate volumetric capacitance of 243.4 F cm −3 at 0.5 A g −1 and an electrode energy density of 33.8 Wh L −1 in 6 M KOH having a limited potential window of 1 V. In another report, Nand oxygen (O)-codoped carbon electrodes were prepared from soybean dregs through time-and energy-consuming multistep heating, including the hydrothermal method at 100 °C for 6 h followed by conventional carbonization at 650 °C for 2 h using KOH as an activating agent. Moreover, the developed material showed an inferior volumetric capacitance of 247.6 F cm −3 and an energy density of 34.3 Wh L −1 at 0.5 A g −1 in 6 M KOH in a limited potential window of 1 V. 22 Similarly, O-doped carbon was prepared via two-step conventional carbonization at 400 °C for 1 h followed by 700 °C for 1 h under an air atmosphere, 23 N-and fluorine (F)-codoped carbon prepared via solvothermal method at 400 °C for 16 h under N 2 atmosphere, 24 phosphorus (P)-and N-codoped carbon prepared via conventional carbonization at 800 °C for 2 h under N 2 atmosphere, 25 N-, P-, and O-tridoped carbon synthesized through electrophilic substitution reaction, 26 have also been investigated.…”

“…The produced AC with abundant micropores exhibited a capacitance of 325 F g −1 at 0.5 F g −1 in 6 M KOH with a limited potential window of 1 V, which was further reduced to 0.8 V in the case of a device with a capacitance of 268.5 F g −1 at 0.5 F g −1 . 28 Few other investigations are also available where heteroatom-doped carbon has been derived from different biomasses using KOH 19 or urea 20 as the dopant/activator; however, they also require the combination of conventional and microwave heating methods. It was also observed that most of the previous methods used corrosive KOH in a high proportion (2−6 times the biomass weight) and/or a longer microwave treatment (3−20 min) in specially designed reactors (as discussed above), which are not favorable for controlling porosity and implementing scale up.…”

Role of ZnO/GO nanocomposite in photocatalytic degradation of mixture of organic pollutants and antimicrobial activity

“…These include lipid peroxidation, oxida-tive stress, proteolysis, ROS induction, and cell membrane lysis. [39,40]…”