S/N Co-Doped Activated Mesoporous Carbon derived from Protein-Rich Dried Pollock for Supercapacitor

S/N Co-Doped Activated Mesoporous Carbon derived from Protein-Rich Dried Pollock for Supercapacitor | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article S/N Co-Doped Activated Mesoporous Carbon derived from Protein-Rich Dried Pollock for Supercapacitor Hyo-Jin Ahn, Gyu-Jin Park This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9164790/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Biomass derived activated carbon has been emerged as alternatives to the depletable resources due to its sustainability and low cost. Large surface area and the optimal pore distribution of micropores, mesopores, and macropores are crucial for achieving high performance activated carbon. Thereby, we synthesized KOH activated carbon derived from protein-rich dried pollack which exhibits mesoporous structure with high surface area. We improved the electrolyte wettability and charge transfer capability by performing a doping process to introduce electrochemically active nitrogen species (graphitic N and pyrrolic N) and functional groups forming surface functionalities (C-N, C-S). 2SN-DP electrode shows the largest specific surface area (2764.8 m 2 g -1 ), favorable pore distribution, nearly capacitive charge storage behavior (b ≈ 0.774), and superior specific capacitance (189.5 F g -1 at a current density of 0.2 A g -1 and 128.52 F g -1 at 20 A g -1 ). The outstanding performance of 2SN-DP electrode was attributed to the interactive effects of improved ion transportation and conductivity provided by KOH activation and N/S co-doping. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The accelerating depletion of fossil fuels and the growing urgency of slowing climate change, the development of sustainable energy storage technologies has become a global issue [1]. Among the various strategies to reduce greenhouse gas emissions, renewable energy sources such as marine, geothermal, and solar have drawn significant attention. However, the need for energy storage system to store generated energy has also become urgent owing to their intermittency and output variability arising from their dependence on fluctuating environmental conditions. Electrochemical energy storage devices, such as lithium-ion batteries [2], fuel cells [3], and electrochemical capacitors (ECs) [4], are promising energy storage devices because of their high efficiency and environmental friendliness. Among them, ECs have the advantages including fast charging and discharging rate, excellent stability, and long cycle performance. Electrochemical capacitors are classified into pseudocapacitors (PCs) and electrical double-layer capacitors (EDLCs) according to the charge storage mechanism. EDLCs store energy through the non-Faradaic reaction, indicating physical adsorption and desorption of electrolyte ions at the electrode-electrolyte interface result in ultrafast charge/discharge rates, high- power density, and long cycle life [5]. Activated carbon has been widely employed as an EDLC electrode material due to its high surface area, low cost, and chemical stability [6]. However, conventional Activated carbon derived from non-renewable sources often suffers from limited conductivity, poor pore size distribution, and low active site density, which interrupt ion transport and high-rate performance. In recent years, biomass-derived carbons came out as sustainable alternatives, offering heteroatom functional groups and tunable pore structures [7]. Biomass precursors such as coconut shells, fruit seeds, and agricultural byproducts have been well explored. Among these, protein-rich biomass is particularly attractive because its nitrogen-containing amino acids can directly serve as in situ N-doping sources during carbonization [8, 9]. Dried pollock (DP) is a protein-rich marine biomass, which can be a novel and sustainable carbon active material for EDLCs applications. Following KOH activation, the protein-rich pollock undergoes structural evolution into a mesoporous framework, which significantly increases the electrochemically active sites. [10]. Furthermore, heteroatom doping has been reported to improve wettability, enhance electrical conductivity, and increase the electrochemically active sites, improving both double-layer capacitance and pseudocapacitive behavior [11]. Hence, we reported the synthesis of N/S co-doped porous carbon materials via KOH activation and heteroatom doping through hydrothermal synthesis. The relationship among doping concentration, pore structure evolution, surface chemistry, and electrochemical performance was systematically analyzed. The optimal sample exhibits a balanced micro–mesoporous structure, with a high density of graphitic/pyrrolic nitrogen and C-S functionalities, resulting in superior capacitive. This study not only demonstrates the potential of KOH activated dried pollack biomass as a high-performance electrode material but also provides insight into the role of controlling heteroatom doping to tailoring carbon structure and surface chemistry for advanced EDLC applications. 2. Experimental section and Methods 2.1. Synthesis of dried pollack derived activated carbons (bare DP) Dried pollack derived activated carbons were synthesized by KOH activation. First, dried pollack was fully dried in the 80 ℃ oven for 12 h to evaporate moisture. After drying, dried pollacks were stabilized in a box furnace at 400 ℃ for 3 h. Stabilized dried pollacks were stirred with nitric acid (HNO 3 , Junsei) to remove impurities. For KOH activation, dried pollack derived activated carbons and potassium hydroxide powders (KOH, Samchun) were mixed by mass ratio of 1:4 with a small amount of DI water. Mixed solution was well dried in the 80 ℃ oven and the brownish black powders were obtained. The powders were carbonized at 800 ℃ for 2 h in the N 2 atmosphere. Heat treated powders were washed using hydrogen chloride (HCl, Samchun) and dried to finally obtain dried pollack derived activated carbons (bare DP). 2.2. S/N co-doped dried pollack derived activated carbons (1SN-DP, 2SN-DP, and 3SN-DP) To synthesize S/N co-doped dried pollack derived activated carbons, hydrothermal method was used as doping strategy. Bare DP and thiourea (SC(NH 2 ) 2 , Sigma-Aldrich) were stirred for 30 min by mass ratio of 1:1, 1:2, and 1:3 with 30 ml Di water. After stirring, homogeneously mixed solutions were heated 180 ℃ for 4 h. Lastly, the solutions were centrifuged at 10,000 rpm for several times to eliminate impurities and S/N co-doped dried pollack derived activated carbons were obtained. These samples were named as 1SN-DP, 2SN-DP, and 3SN-DP. 2.3. Characterizations The morphology image of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were obtained using high-resolution scanning electron microscopy (HR-SEM, Hitachi). Crystal structures of four samples were revealed by X-ray diffraction (XRD) in a range of 10 ◦ to 90 ◦ . X-ray photoelectron spectroscopy (XPS) was performed to clarify the chemical bonding status of the surface. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were used to track the mass variation with the temperature range from 0 ℃ to 900 ℃ in the air atmosphere. The surface pore distribution was measured by Brunauer-Emmett-Teller (BET). 2.4. Electrochemical performances Electrodes were fabricated to measure the electrical performance of each sample. Bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were used as an active material, respectively, accounting for 80 wt% of the total mass of electrode. 10 wt% of ketjen black as a conductive material and 10 wt% of polyvinylpyrrolidone (PVDF, Sigma-Aldrich) as a binder were also used to prepare electrode slurry mixtures. All these materials were well dispersed by NMP solvent (Sigma-Aldrich). The slurry mixtures were casted on the nickel foam and dried 12 h at 80 ℃. Electrochemical measurements were conducted using an autolab potentiostat/galvanostat. The measurement was carried out based on two electrode system made up of a beaker-type supercapacitor cell composed of two electrodes which were fabricated by synthesized activated carbon and 6 M KOH dissolved aqueous electrolyte. The charge/discharge test was carried out at 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A. And cyclic voltammetry (CV) curves were performed at diverse scan rates of 20, 40, 60, 80, and 100 mV s -1 in the range of 0 V to 1 V. 3. Results and discussion Bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were successfully synthesized by KOH activation process using dried pollack and doping process through hydrothermal method. Stabilization process and KOH activation process were performed to use dried pollack as activated carbon. KOH activation process was performed to form a porous carbon with a high specific surface area. During KOH activation the reaction shown in the following equation has occurred (1)–(3) [12]. 6KOH + 2C → 2K + 3H + 2KCO (1) K 2 CO 3 → K 2 O + CO or K 2 CO 3 + C → K 2 O + CO 2 (2) 2K + CO → KO + CO (3) Doping process via hydrothermal synthesis was introduced to KOH activated dried pollack to tunning surface chemistry that enhancing electron conductivity and facilitating ion transportation. By N/S co-doping using thiourea, activated dried pollack provided a balanced pore structure due to the reaction of the carbon structure and the released gas during doping process [13]. Figure 1 represent HR-SEM images of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. All samples show porous surface, irregular particle size and shape, respectively. Figure 1 (c and g), 2SN-DP notably exhibits a highly porous structure, indicating S/N co-doping induced the uniform development of homogeneously and valanced micropore and mesopore distribution across the entire surface. In contrast, the Fig. 1 (d and e), 3SN-DP displayed partial pore coalescence and surface densification, suggesting that excessive S/N co-doping leads to structural collapse. It indicates that an appropriate amount of S/N co-doping effectively activates the carbon matrix, enhancing ion accessibility and providing high-surface-area frameworks suitable for electrochemical applications [14]. Figure 2 shows BET results of all synthesized samples. Bare DP, 1SN-DP, 2SN-DP, and 3SN-DP exhibit the shape of a type Ⅳ isotherm hysteresis loop, indicating all samples are highly mesoporous [15]. The pore structure of the activated carbons were significantly influenced by the concentration of dopants. As shown in Fig. 2 (d), 1SN-DP and 2SN-DP samples exhibited enhanced surface areas of 3,099.9 m² g⁻¹ and 3,267.1 m² g⁻¹, compared to bare DP respectively. This enhancement can be attributed to the chemical etching effect during the hydrothermal doping processes. During the thermal treatment, the reaction between carbon atoms and doping precursors occurs that releases gaseous byproducts, which creates new mesopores and micropores on the carbon surface and refines the pore network [16]. Notably, the 2SN-DP sample showed the highest specific surface area among all samples. While the specific surface area increased, the average pore diameter decreased from 3.46 nm to 2.91. It suggests that the doping process induced a structural rearrangement which converts macropores into mesopores and micropores. These changes are crucial because it greatly increases the number of adsorption sites per unit mass, which enhancing specific surface area [17]. Such a highly developed specific surface area in 2SN-DP is important for providing extensive electrode-electrolyte interfaces, promoting electric double layer formation and accommodating pseudo-capacitive reactions contributed by the heteroatoms S and N introduced through doping. However, as the doping concentration increases, the structure collapsed. The 3SN-DP sample displayed a reduced specific surface area (2597.5 m² g⁻¹) and the lowest total pore volume (1.9589 m² g⁻¹). This degradation indicates that an excessive amount of doping agents caused the collapse of the fragile pore walls and led to the agglomeration of dopants that physically blocked the pore channels. Consequently, this blockage led to limited electrolyte accessibility. Figure 3 presents XRD patterns of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. All samples revealed broad diffraction peaks at around 2θ = 24° and 43°, corresponding to the (002) and (100) planes of amorphous carbon, respectively. All samples show consistent peak positions and widths which suggest that S/N co-doping does not significantly affect the activated dried pollack’s crystallinity and bring out new crystalline phases. This observation suggests that the doping process mainly influences the surface chemistry and pore structure of the activated carbon derived from dried pollack, while the overall crystallinity unchanged and no additional crystalline phases are formed. Figure 4 indicate thermogravimetric analysis (TGA) and differential thermal analysis (DTA) curves. TGA and DTA were used to trace the thermal stability and compositional differences among the samples in a range of 25–900°C in the air condition. Bare DP exhibits two major weight loss stages and 1SN-DP, 2SN-DP, and 3SN-DP exhibits three major weight loss stages. Initial loss below 100°C attributed to moisture and volatile impurities [18]. Around 250 ~ 350°C, 1SN-DP, 2SN-DP, and 3SN-DP exhibit major decomposition and endothermic peaks due to the decomposition of bonded surface functional groups [19]. Above 500°C, carbon decomposition begins, lattice rearrangement occurs due to carbon decomposition, and a strong exothermic peak appears [20]. The decomposition reaction of surface functional groups at 250 ~ 350°C indicates that surface functional groups were provided due to doping and more surface functional groups were generated as the amount of doping increased. Figure 5 X-ray photoelectron spectroscopy (XPS) analyses were conducted to clarify the chemical bonding of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. In Fig. 5 (a), the C 1s X-ray photoelectron spectrum shows that all samples comprise three major peaks at approximately 284.5, 286.1, and 287.1 eV, signifying C-C, C-O, and C = O, respectively. In particular, 1SN-DP, 2SN-DP, and 3SN-DP include two peaks related to doping at approximately 285.1 and 285.6 corresponding to C-S and C-N. 2SN-DP shows the largest peak area of C-C bonding which implies S/N co-doping promoted graphitization, forming π-π electron conduction path [21]. Notably, 3SN-DP shows smallest area of C-C, C-S, and C-N bonding among all samples. It indicates that excessive doping interrupts graphitization and heteroatoms fail to react reliably with the carbon lattice, resulting in forming defects. In Fig. 5 (b), the O 1s X-ray photoelectron spectrum presents three bonding states at ~ 530.6, ~ 531.5, and ~ 532.9 eV, corresponding to O = C, HO-C, and O = C-C. As the amount of doping source increases, HO-C bonding peak increases and facilitates ion affinity. 3SN-DP shows an excessive amount of HO-C bonding, which means that heteroatoms such as S and N cannot enter the lattice stably and formed defects outside the framework, creating excessive functional groups disturbing electron and ion transportation. Figure 5 (c) exhibits that the N 1s X-ray photoelectron spectrum consist of four peaks at approximately 398.7, 399.9, 401.4, and 403.3 eV, corresponding to pyridine N, pyrrolic N, graphitic N, and oxidized N [22]. Among 1SN-DP, 2SN-DP, and 3SN-DP, 2SN-DP exhibits the largest area corresponding to the bonding state of graphitic N and pyrrolic N. Graphitic N enhances the electrical conductivity of the carbon matrix by promoting π-electron delocalization and improving structural order. Pyrrolic N contributes to the faradic redox reaction, providing additional pseudocapacitive behavior and improving ion accessibility. It enhances electron conductivity and pseudocapacitive behavior which leads to improve electrochemical performance of 2SN-DP [23]. Figure 5 (d) presents that the S 2p X-ray photoelectron spectrum consist of two peaks at ~ 164.1, and ~ 165.2 eV, indicating C-S-C 2p 1/2 , and C-S-C 2p 3/2 , respectively. All samples exhibit two peaks, but conspicuously the 2SN-DP sample exhibits the most well-defined spin–orbit doublet, with a sharp and symmetric peak shape, suggesting sulfur atoms well doped within the carbon lattice due to the optimized doping concentration [24, 25]. In contrast, the 1SN-DP and 3SN-DP show poorly resolved peaks with diminished intensity, suggesting sulfur doping is not well-formed within the carbon lattice. In Fig. 6 , cyclic voltammetry (CV) profiles, as expected, 2SN-DP shows the largest area closest to the rectangular. The bare DP electrode exhibits distorted, non-rectangular CV curves, indicating sluggish ion transport and limited double-layer formation. Furthermore, distortion of the rectangular shape of CV curves becomes more pronounced as the scan rate increases, which implies poor rate capacity. In contrast, the 2SN-DP electrode retains semi-rectangular shape even at high scan rates, suggesting excellent rate capability and efficient ion accessibility [26, 27]. Notably, 3SN-DP electrode shows a slightly improved rectangular shape compared to the bare DP electrode, but a distorted rectangular shape compared to the 2SN-DP electrode, implying that excessive doping interrupted rapid ion diffusion and block active sites. In Fig. 7 (a), to define the charge storage mechanism, scan rate and peak current were analyzed in detail through the power law equation i = a v b . In Fig. 7 , Log i -log v plots yielded b-values of 0.652, 0.769, 0.774, and 0.649 for bare DP, 1SN-DP, 2SN-DP, and 3SN-DP, respectively. The 2SN-DP sample exhibits the highest b-value (0.774), confirming its capacitive-diffusion mixed energy storage mechanism [28]. As 2SN-DP shows capacitive behavior, it retained the quasi-rectangular CV profiles even at high scan rates, confirming the ability to sustain rapid ion diffusion and efficient electronic conductivity under fast charge-discharge condition [29]. The low b-value of 3SN-DP suggests that excessive doping induces pore blockage, which lengthens effective diffusion paths and lowers accessible surface on the time scale of fast scans. In Fig. 7 (b) the Nyquist plots of the 2SN-DP electrode notably exhibited the lowest charge-transfer resistance (R ct ) in comparison with the Bare DP and other doped samples. This significant reduction was caused by the interactive effect of the optimized surface functionalization and pore distribution. The chemical etching during the S/N co-doping process helps to form interconnection of channels between micropores and mesopores within the carbon matrix. This well-developed porous network minimizes the resistance for electrolyte penetration, leading to the fast ion diffusion rate at the interface of electrode-electrolyte comparison with the Bare DP. Moreover, the 2SN-DP electrode showed the largest slope of the graph, indicating the most efficient ion diffusion rate in the electrolyte. This superior electrochemical behavior is derived from improved electrical conductivity resulting from the incorporation of sulfur and nitrogen heteroatoms. The doping introduces electron-rich sites into the carbon lattice, which produces extra electrons to the conduction band and induces the delocalization of electrons [30]. This modification effectively lowers the intrinsic resistance of the material, facilitating faster electron transport in the charge-storage process. Consequently, 2SN-DP demonstrated the highest electrochemical conductivity and ideal capacitive behavior among all prepared samples [31]. Figure 8 (a-d) presents the GCD curves of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP measured at diverse current densities. All electrodes show the typical charge/discharge profiles. The 2SN-DP sample exhibited the longest discharge time due to enhanced electron conduction and ion transportation, development of uniform micro-mesopores, and increased active sites via doping. Figure 8 (e) presents the specific capacitance values of all samples derived from galvanostatic charge–discharge (GCD) curves. C sp was derived using the following Eq. ( 4 ). $$\:{C}_{sp}=\frac{I\:\times\:\:\varDelta\:t}{m\:\times\:\:\varDelta\:V}$$ 4 \(\:\) The specific capacitances of the bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were calculated to 127.0, 184.9, 189.5, and 161.2 F g -1 at 0.2 A g -1 . Table 2 shows the specific capacitance of all electrodes at 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A g -1 , respectively. 2SN-DP electrode performed the highest capacitance value in all section, suggesting well doped activated carbon exhibits superior high-rate performance. 3SN-DP showed the smallest specific surface area but performed better capacitance performance than bare DP. It implies that changes in pore distribution through doping also affected the electrochemical performance, in particular formation of surface functional groups and N, S doping sites significantly contributes to electrochemical performance improvement. Table 1 BET and BJH result of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP Samples S BET [m 2 g -1 ] Total pore volume [P/P 0 = 0.990] [cm 3 g -1 ] Average pore diameter [nm] Pore size distribution V micro (%) V meso (%) V macro (%) Bare DP 2880.4 2.4911 3.4593 52.491 46.842 0.667 1SN-DP 3099.9 2.3223 2.9697 52.561 46.925 0.514 2SN-DP 3267.1 2.4027 2.9072 54.982 46.400 0.440 3SN-DP 2597.5 1.9589 3.2684 54.796 44.689 0.515 Table 2 Specific capacitance of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP Samples Specific capacitance (C sp , F g -1 ) 0.2 A g -1 0.5 A g -1 1 A g -1 2 A g -1 3 A g -1 5 A g -1 7 A g -1 10 A g -1 15 A g -1 20 A g -1 Bare DP 127.0 120.8 114.8 109.6 105.6 100 95.2 92.3 84.1 80.7 1SN-DP 184.9 182.1 172.4 164.5 158.4 148.7 140.2 128.3 114.6 108.6 2SN-DP 189.5 182.3 172.8 166.8 162.2 154.8 151.2 144.1 132.7 128.5 3SN-DP 161.2 158.4 151.2 144.1 139.6 132.5 127.2 120.4 112.8 108.4 4. Conclusions In this study, 2SN-DP was successfully synthesized by KOH activation and heteroatom doping via hydrothermal synthesis. KOH activation generated a highly mesoporous structure resulting in the largest specific surface area and doping process introduced the functional groups on surface which are favorable for high-efficient EDLCs. To determine the optimal doping ratio, the amount of doping precursor added during synthesis was adjusted to three levels, corresponding to mass ratios of bare DP to doping precursor of 1:1, 1:2, and 1:3. Optimal doping with a mass ratio of carbon-to-doping source 1:2 was applied to 2SN-DP sample, which optimally formed high specific surface area via gas-releasing decomposition during pyrolysis, which provides abundant active sites for ion adsorption, significantly facilitating the development of the electric double layer and thereby enhancing the overall energy storage capacity. Doping process also facilitated the incorporation of electrochemically active nitrogen species (graphitic N and pyrrolic N), and enhanced the surface functionalities (C-N, C-S), leading to improved electrolyte wettability and charge transfer capability. This resulted in the superior specific surface area (3267.1m 2 g-1), favorable pore distribution, and nearly capacitive charge storage behavior (b ≈ 0.774). Specifically, the CV curves of 2SN-DP showed a symmetric quasi-rectangular profile typical of EDLCs, with a significantly larger CV curve area compared to Bare DP. This confirms that the heteroatom doping successfully enhanced the overall charge storage capacity which can improve specific capacitance (189.5 F g -1 at a current density of 0.2 A g -1 , 128.52 F g -1 at 20 A g -1 ). In contrast, insufficient doping (1SN-DP) produced limited porosity and reduced functionalization, while excessive doping (3SN-DP) induced partial pore blockage and an increased proportion of -OH groups that hinders ion transport, shifting the charge storage toward a diffusion-controlled process. The results demonstrate that controlled heteroatom doping finely tune both the physical structure and the chemical composition of carbon materials, maximizing their electrochemical performance for energy storage applications. Thus, 2SN-DP could be an attractive active material for high performance supercapacitor. Declarations Declaration of Competing Interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This study was supported by the Research Program funded by the SeoulTech (Seoul National University of Science and Technology) References W. Xu, G.Wang, S. Liu, J. Wang, W.H. Mcdaowell, K. Huang, P.A. Raymong, Z. Yang, X. Xia, Globally elevated greenhouse gas emissions from polluted urban rivers. Nat. Sustain. 7, 938–948 (2024) J. Liu, Z. Bao, Y. Cui, E.J. Dufek, J.B. Goodenough, P. Khalifah, Q. Li, B.Y. Liaw, P. Liu, A. Manthiram, Y.S. Meng, V.R. Subramanian, M.F. Toney, V.V. Viswanathan, M.S. Whittingham, J. Xiao, W. Xu, J. Yang, X.Q. Yang, J.G. Zhang, Pathways for practical high-energy long-cycling lithium metal batteries. Nat. Energy 4, 180–186 (2019) X. Tian, X. Zhao, Y.Q. Su, L. Wang, H. Wang, D. Dang, B. Chi, H, Liu, E.J.M. Hensen, X.W. Lou, B.Y. Xia, Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells. Electrochemistry 366, 6467 (2019) G Xu, J. Han, B. Ding, P. Nie, J, Pan, H. Dou, H. Li, X. Zhang, Biomass-derived porous carbon materials with sulfur and nitrogen dual-doping for energy storage. Green Chem. 17, 1668 (2015) G.-H. An, S.-N. Cha, H.-J. Ahn, Surface functionalization of the terraced surface-based current collector for a supercapacitor with an improved energy storage performance. Appl. Surf. Sci. 478, 435–440 (2019) J. Zhang, Y.L. Xie, Hierarchical porous hollow of carbon spheres with high surface area for high performance supercapacitor electrode materials. Sci Rep 15, 15125 (2025) G. Zhong, S. Xu, J. Chao, X. Fu, W. Liao, Y. Xu, Z. Liu, Y. Cao, Biomass derived nitrogen-doped porous carbons activated by magnesium chloride as ultrahigh performance supercapacitors. Ind. Eng. Chem. Res. 59, 21756–21767 (2020) M.-H. Jo, H.-J. Yoon, H.-J. Ahn, Pre‑nitrogen doping effects on mesoporous activated carbon derived from passiflora edulis for high‑performance supercapacitors. Korean J. Chem. Eng. 43, 337–349 (2026) K.-H. Kim, Y.-J. Song, H.-J. Ahn, N-doped mesoporous activated carbon derived from protein-rich biomass. Korean J. Chem. Eng. 40, 1071–1076 (2023) for energy storage applications W. Chen, M. Gong, K. Li, M. Xia, Z. Chen, H. Xiao, Y. Fang, Y. Chen, H. Yang, H. Chen, Insight into KOH activation mechanism during biomass pyrolysis: chemical reactions between O-containing groups and KOH. Appl. Energy 278, 115730 (2020) D. Guo, Z. Li, P. Liu, M. Sun, N, P, S co-doped biomass-derived hierarchical porous carbon through simple phosphoric acid assisted activation for high-performance electrochemical energy storage. Int. J. Hydrog. Energy 46, 8197–8209 (2021) J. Wang, T. Huo, Y. Zhao, R. Lu, X. Wu, Recent advances in heteroatoms-doped porous carbon electrode materials for supercapacitors: A review. J. Energy Storage 110, 115216 (2025) D. Wang, H. Dong, D. Zhang, C. Wang, K. Lu, M. Shi, G. Tong, In-situ template-assisted self-activation craft for direct preparing mesoporous-dominated N/S co-doped hierarchical porous carbon for supercapacitors. Int. J. Biol. Macromol. 305, 141361 (2025) H. Rustamaji, T. Prakoso, H. Devianto, P. Widiatmoko, K.A. Kurnia, Facile synthesis of N, S-modified activated carbon from biomass residue for promising supercapacitor electrode applications. Bioresour. Technol. Rep 21, 101301 (2023) Y. Yardim, I. Genel, C. Saka, Enhanced supercapacitor performance of hierarchical mesoporous sulfur-doped carbon particles from biomass waste for energy storage. Int. J. Hydrog. Energy 99, 383–393 (2025) J. Han, Q. Li, C. Peng, N. Shu, F. Pan, J. Wang, Y. Zhu, Increasing S dopant and specific surface area of N/S-codoped porous carbon y in-situ polymerization of PEDOT into biomass precursor for high performance supercapacitor. Appl. Surf. Sci. 502, 144191 (2020) M. Jiang, X. Yu, R. Gao, T. Yang, Z. Xu, L. Cao, Fabrication of biomass-derived N, S co-doped carbon with hierarchically porous architecture for high performance supercapacitor. Nano 15, 2050096 (2020) O. Zanella, D. Bilibio, W.L. Priamo, Porous structure and characterization of activated carbons from the grape stalks. SusProc. 1, 138473 (2025) J. Zhang, S. Li, B. Tang, Z. Wang, G. Ji, W. Huang, J. Wang, High photocatalytic performance of two types of graphene modified TiO 2 composite photocatalysts. Nano Express 12, 457 (2017) H. Liu, Y. Zhang, R. Li, X. Sun, H. Abou-Rachid, Thermal and chemical durability of nitrogen-doped carbon nanotubes. J. Nanopart. Res. 14, 1016 (2012) H. Jia, J. Sun, X. Xie, K. Yin, L. Sun, Cicada slough-derived heteroatom incorporated porous carbon for supercapacitor: ultra-high gravimetric capacitance. Carbon 143, 309–317 (2029) C.-Y. Lee, H.-J. Ahn, Electrochemical performance of reduced graphyne oxide and biomass-derived activated carbon composite for energy storage devices. J. Porous Mat. 32, 1519–1530 (2025) L. Ji, B. Wang, Y. Yu, N. Wang, J. Zhao, N, S co-doped biomass derived carbon with sheet-like microstructures for supercapacitors. Electrochim. Acta 331, 135348 (2020) V. Thirumal, T.V.M. Sreekanth, K.-S. Yoo, J.-H. Kim. Biomass-derived hard carbon and nitrogen-sulfur co-doped graphene for high-performance symmetric sodium ion capacitor devices. Energies 16, 802 (2023) Y. Li, G. Wang, T. Wei, Z. Fan, P. Yen, Nitrogen and sulfur co-doped porous carbon nanosheets derived from willow catkin for supercapacitors. Nano Energy 19, 165–175 (2016) A. Borenstein, O. Hanna, R. Attias, S. Luski, T. Brousse, D. Aurbach, Carbon based composite materials for supercapacitor electrodes: a review. J. Mater. Chem. A 5, 12653 (2017) R. Dev, H. Gupta, H. Gahtori, H.K. Rathore, M. Hariram, M. Kumar, P.W. Menezes, D. Sarkar, Sustainable activated carbon for aqueous and flexible zinc-ion energy storage. Carbon 245, 120762 (2025) J. Qi, C. Zhang, M. Huang, M. Zhang, T. Li, M. Shi, Z. Wei, J, Ni, Q. Li, Y. Sui, Q. Meng, B. Xiao, F. Wei, L. Zhu, R. Shao, Defect engineering of porous carbon with high N/S doping for potassium ion storage. Appl. Surf. Sci. 657, 159771 (2024) Y. Liao, Z. Shang, G. Ju, D. Wang, Q Yang, Y. Wang, S. Yuan, Biomass derived N-doped porous carbon made from reed straw for an enhanced supercapacitor. Molecules 28, 4633 (2023) G. Zhao, Y. Li, G. Zhu, J. Shi, T. Lu, L. Pan, Biomass-based N, P, and S self-doped porous carbon for high-performance supercapacitors. ACS Sustain. Chem. Eng. 7, 12052–12060 (2019) X. Yang, X. Wang, B. Lu, B. Huang, Y. Xia, G. Lin, Biomass-derived N, S co-doped activated carbon-polyaniline nanorod composite electrodes for high-performance supercapacitors. Appl. Surf. Sci. 639, 158191 (2023) Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 26 Mar, 2026 Reviewers invited by journal 26 Mar, 2026 Editor assigned by journal 25 Mar, 2026 First submitted to journal 18 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Ahn","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIie3RMQrCMBSA4VcCurR0rRTqFVoKircxeAIX6VBqgmAXD2BBPINT50igXXKADg6K0LmTuAimbi5p3RzyD+GF8JFAAHS6P8wHNgCI2hERubDP1IOIdjQo6UlgAMb2FzI1eH1fHhPPdnB6beIL2ClDYaQgM1JMwyzn4WiPKd0XNThijrBQPYyxiWvlDJ8qTDcW4QAVoDNRkvLhWodk/SEvScbdRMhbCJr7LTEk8SXBHWTlmgUPst2NZruCm4HAm0BJqjJ3zTgZ28MFa54x97yS85GKgMO+96b8ICUAsDvOdTqdTgdvuyxWMdPEHLwAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-5786-3937","institution":"Seoul National University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Hyo-Jin","middleName":"","lastName":"Ahn","suffix":""},{"id":612953436,"identity":"5cee35c3-fbe8-4c4e-a5d0-610703668e06","order_by":1,"name":"Gyu-Jin Park","email":"","orcid":"","institution":"Seoul National University of Science \u0026 Technology","correspondingAuthor":false,"prefix":"","firstName":"Gyu-Jin","middleName":"","lastName":"Park","suffix":""}],"badges":[],"createdAt":"2026-03-19 04:25:02","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9164790/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9164790/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105904214,"identity":"1b02024f-06fb-4417-a970-2dce54a38823","added_by":"auto","created_at":"2026-04-01 10:06:21","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":607397,"visible":true,"origin":"","legend":"\u003cp\u003eHR-SEM images of (a and e) bare DP, (b and f) 1SN-DP, (c and g) 2SN-DP, and (d and h) 3SN-DP\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/28971c6daff0fd205abc3a96.png"},{"id":105753418,"identity":"7729e1d9-303c-480a-b571-ab591bb3c57d","added_by":"auto","created_at":"2026-03-30 16:08:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":483173,"visible":true,"origin":"","legend":"\u003cp\u003e(a) N\u003csub\u003e2\u003c/sub\u003e adsorption volume profiles of bare DP, 1SN-DP, 2SN-DP and 3SN-DP, pore volume distributions according to the pore diameter of (b) 0.4-180 nm, and (c) 0.4-2 nm, (d) Specific surface area of all activated carbon\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/fdb251c5df0aecf1be127cbd.png"},{"id":105753414,"identity":"882cf00f-f7ad-4d49-bd6e-9235c8f6304a","added_by":"auto","created_at":"2026-03-30 16:08:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":236058,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of bare DP, 1SN-DP, 2SN-DP and 3SN-DP in the 2θ range from 10° to 90°\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/373110e4f2fbffdedc6b898a.png"},{"id":105753420,"identity":"74c37075-a66a-44e6-bd1f-c0e8f4cb7997","added_by":"auto","created_at":"2026-03-30 16:08:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":520075,"visible":true,"origin":"","legend":"\u003cp\u003eTGA-DTA profile of (a) bare DP, (b) 1SN-DP, (c) 2SN-DP and (d) 3SN-DP\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/402b6923e2796193f0bf7c2a.png"},{"id":105753417,"identity":"2bbabd04-e84f-44d0-bd81-f47de36123ab","added_by":"auto","created_at":"2026-03-30 16:08:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":685700,"visible":true,"origin":"","legend":"\u003cp\u003eXPS data of (a) C 1s, (b) O 1s, (c) N 1s and (d) S 2p of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/a430ddcd66226d21bab7ce4d.png"},{"id":105753419,"identity":"6f77a9c9-d321-474d-af59-d9961742762f","added_by":"auto","created_at":"2026-03-30 16:08:58","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":598224,"visible":true,"origin":"","legend":"\u003cp\u003eCV curves of (a) bare DP, (b) 1SN-DP, (c) 2SN-DP and (d) 3SN-DP electrodes in the voltage range from 0 V to 1 V\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/63a5d480cc6c1f4f9e443b0c.png"},{"id":105753412,"identity":"fcbb0087-ab81-4115-ab25-7d5071d2b884","added_by":"auto","created_at":"2026-03-30 16:08:58","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":210506,"visible":true,"origin":"","legend":"\u003cp\u003e(a) b-value plots of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP, (b) Nyquist plots of all electrodes\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/c64c51fc5119b25ac0fecbc4.png"},{"id":105753451,"identity":"e712560e-970a-4ba7-a6fc-849d0d8b5377","added_by":"auto","created_at":"2026-03-30 16:09:20","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":677442,"visible":true,"origin":"","legend":"\u003cp\u003eThe galvanostatic charge-discharge (GCD) curves of (a) bare DP, (b) 1SN-DP, (c) 2SN-DP and (d) 3SN-DP electrodes at the current densities of 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A g\u003csup\u003e-1\u003c/sup\u003e. (e) Specific capacitance of bare DP, 1SN-DP, 2SN-DP and 3SN-DP electrodes at the current densities of 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A g\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/c0bdc38dc1bed61737559885.png"},{"id":106092983,"identity":"baa44f8b-6543-4449-8f36-24b3d396a9c4","added_by":"auto","created_at":"2026-04-03 11:31:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4806896,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9164790/v1/e1452ed9-f5b3-4c39-945c-66a5adaadaa2.pdf"}],"financialInterests":"","formattedTitle":"S/N Co-Doped Activated Mesoporous Carbon derived from Protein-Rich Dried Pollock for Supercapacitor","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe accelerating depletion of fossil fuels and the growing urgency of slowing climate change, the development of sustainable energy storage technologies has become a global issue [1]. Among the various strategies to reduce greenhouse gas emissions, renewable energy sources such as marine, geothermal, and solar have drawn significant attention. However, the need for energy storage system to store generated energy has also become urgent owing to their intermittency and output variability arising from their dependence on fluctuating environmental conditions. Electrochemical energy storage devices, such as lithium-ion batteries [2], fuel cells [3], and electrochemical capacitors (ECs) [4], are promising energy storage devices because of their high efficiency and environmental friendliness. Among them, ECs have the advantages including fast charging and discharging rate, excellent stability, and long cycle performance. Electrochemical capacitors are classified into pseudocapacitors (PCs) and electrical double-layer capacitors (EDLCs) according to the charge storage mechanism. EDLCs store energy through the non-Faradaic reaction, indicating physical adsorption and desorption of electrolyte ions at the electrode-electrolyte interface result in ultrafast charge/discharge rates, high- power density, and long cycle life [5]. Activated carbon has been widely employed as an EDLC electrode material due to its high surface area, low cost, and chemical stability [6]. However, conventional Activated carbon derived from non-renewable sources often suffers from limited conductivity, poor pore size distribution, and low active site density, which interrupt ion transport and high-rate performance. In recent years, biomass-derived carbons came out as sustainable alternatives, offering heteroatom functional groups and tunable pore structures [7]. Biomass precursors such as coconut shells, fruit seeds, and agricultural byproducts have been well explored. Among these, protein-rich biomass is particularly attractive because its nitrogen-containing amino acids can directly serve as in situ N-doping sources during carbonization [8, 9]. Dried pollock (DP) is a protein-rich marine biomass, which can be a novel and sustainable carbon active material for EDLCs applications. Following KOH activation, the protein-rich pollock undergoes structural evolution into a mesoporous framework, which significantly increases the electrochemically active sites. [10]. Furthermore, heteroatom doping has been reported to improve wettability, enhance electrical conductivity, and increase the electrochemically active sites, improving both double-layer capacitance and pseudocapacitive behavior [11]. Hence, we reported the synthesis of N/S co-doped porous carbon materials via KOH activation and heteroatom doping through hydrothermal synthesis. The relationship among doping concentration, pore structure evolution, surface chemistry, and electrochemical performance was systematically analyzed. The optimal sample exhibits a balanced micro\u0026ndash;mesoporous structure, with a high density of graphitic/pyrrolic nitrogen and C-S functionalities, resulting in superior capacitive. This study not only demonstrates the potential of KOH activated dried pollack biomass as a high-performance electrode material but also provides insight into the role of controlling heteroatom doping to tailoring carbon structure and surface chemistry for advanced EDLC applications.\u003c/p\u003e"},{"header":"2. Experimental section and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Synthesis of dried pollack derived activated carbons (bare DP)\u003c/h2\u003e \u003cp\u003eDried pollack derived activated carbons were synthesized by KOH activation. First, dried pollack was fully dried in the 80 ℃ oven for 12 h to evaporate moisture. After drying, dried pollacks were stabilized in a box furnace at 400 ℃ for 3 h. Stabilized dried pollacks were stirred with nitric acid (HNO\u003csub\u003e3\u003c/sub\u003e, Junsei) to remove impurities. For KOH activation, dried pollack derived activated carbons and potassium hydroxide powders (KOH, Samchun) were mixed by mass ratio of 1:4 with a small amount of DI water. Mixed solution was well dried in the 80 ℃ oven and the brownish black powders were obtained. The powders were carbonized at 800 ℃ for 2 h in the N\u003csub\u003e2\u003c/sub\u003e atmosphere. Heat treated powders were washed using hydrogen chloride (HCl, Samchun) and dried to finally obtain dried pollack derived activated carbons (bare DP).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. S/N co-doped dried pollack derived activated carbons (1SN-DP, 2SN-DP, and 3SN-DP)\u003c/h2\u003e \u003cp\u003eTo synthesize S/N co-doped dried pollack derived activated carbons, hydrothermal method was used as doping strategy. Bare DP and thiourea (SC(NH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, Sigma-Aldrich) were stirred for 30 min by mass ratio of 1:1, 1:2, and 1:3 with 30 ml Di water. After stirring, homogeneously mixed solutions were heated 180 ℃ for 4 h. Lastly, the solutions were centrifuged at 10,000 rpm for several times to eliminate impurities and S/N co-doped dried pollack derived activated carbons were obtained. These samples were named as 1SN-DP, 2SN-DP, and 3SN-DP.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Characterizations\u003c/h2\u003e \u003cp\u003eThe morphology image of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were obtained using high-resolution scanning electron microscopy (HR-SEM, Hitachi). Crystal structures of four samples were revealed by X-ray diffraction (XRD) in a range of 10\u003csup\u003e◦\u003c/sup\u003e to 90\u003csup\u003e◦\u003c/sup\u003e. X-ray photoelectron spectroscopy (XPS) was performed to clarify the chemical bonding status of the surface. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were used to track the mass variation with the temperature range from 0 ℃ to 900 ℃ in the air atmosphere. The surface pore distribution was measured by Brunauer-Emmett-Teller (BET).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Electrochemical performances\u003c/h2\u003e \u003cp\u003eElectrodes were fabricated to measure the electrical performance of each sample. Bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were used as an active material, respectively, accounting for 80 wt% of the total mass of electrode. 10 wt% of ketjen black as a conductive material and 10 wt% of polyvinylpyrrolidone (PVDF, Sigma-Aldrich) as a binder were also used to prepare electrode slurry mixtures. All these materials were well dispersed by NMP solvent (Sigma-Aldrich). The slurry mixtures were casted on the nickel foam and dried 12 h at 80 ℃. Electrochemical measurements were conducted using an autolab potentiostat/galvanostat. The measurement was carried out based on two electrode system made up of a beaker-type supercapacitor cell composed of two electrodes which were fabricated by synthesized activated carbon and 6 M KOH dissolved aqueous electrolyte. The charge/discharge test was carried out at 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A. And cyclic voltammetry (CV) curves were performed at diverse scan rates of 20, 40, 60, 80, and 100 mV s\u003csup\u003e-1\u003c/sup\u003e in the range of 0 V to 1 V.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eBare DP, 1SN-DP, 2SN-DP, and 3SN-DP were successfully synthesized by KOH activation process using dried pollack and doping process through hydrothermal method. Stabilization process and KOH activation process were performed to use dried pollack as activated carbon. KOH activation process was performed to form a porous carbon with a high specific surface area. During KOH activation the reaction shown in the following equation has occurred (1)\u0026ndash;(3) [12].\u003c/p\u003e\n\u003ch3\u003e6KOH + 2C → 2K + 3H + 2KCO (1)\u003c/h3\u003e\n\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e \u0026rarr; K\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;CO or K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;C \u0026rarr; K\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;CO\u003csub\u003e2\u003c/sub\u003e (2)\u003c/p\u003e\n\u003ch3\u003e2K + CO → KO + CO (3)\u003c/h3\u003e\n\u003cp\u003eDoping process via hydrothermal synthesis was introduced to KOH activated dried pollack to tunning surface chemistry that enhancing electron conductivity and facilitating ion transportation. By N/S co-doping using thiourea, activated dried pollack provided a balanced pore structure due to the reaction of the carbon structure and the released gas during doping process [13]. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e represent HR-SEM images of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. All samples show porous surface, irregular particle size and shape, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(c and g), 2SN-DP notably exhibits a highly porous structure, indicating S/N co-doping induced the uniform development of homogeneously and valanced micropore and mesopore distribution across the entire surface. In contrast, the Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d and e), 3SN-DP displayed partial pore coalescence and surface densification, suggesting that excessive S/N co-doping leads to structural collapse. It indicates that an appropriate amount of S/N co-doping effectively activates the carbon matrix, enhancing ion accessibility and providing high-surface-area frameworks suitable for electrochemical applications [14].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows BET results of all synthesized samples. Bare DP, 1SN-DP, 2SN-DP, and 3SN-DP exhibit the shape of a type Ⅳ isotherm hysteresis loop, indicating all samples are highly mesoporous [15]. The pore structure of the activated carbons were significantly influenced by the concentration of dopants. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(d), 1SN-DP and 2SN-DP samples exhibited enhanced surface areas of 3,099.9 m\u0026sup2; g⁻\u0026sup1; and 3,267.1 m\u0026sup2; g⁻\u0026sup1;, compared to bare DP respectively. This enhancement can be attributed to the chemical etching effect during the hydrothermal doping processes. During the thermal treatment, the reaction between carbon atoms and doping precursors occurs that releases gaseous byproducts, which creates new mesopores and micropores on the carbon surface and refines the pore network [16]. Notably, the 2SN-DP sample showed the highest specific surface area among all samples. While the specific surface area increased, the average pore diameter decreased from 3.46 nm to 2.91. It suggests that the doping process induced a structural rearrangement which converts macropores into mesopores and micropores. These changes are crucial because it greatly increases the number of adsorption sites per unit mass, which enhancing specific surface area [17]. Such a highly developed specific surface area in 2SN-DP is important for providing extensive electrode-electrolyte interfaces, promoting electric double layer formation and accommodating pseudo-capacitive reactions contributed by the heteroatoms S and N introduced through doping. However, as the doping concentration increases, the structure collapsed. The 3SN-DP sample displayed a reduced specific surface area (2597.5 m\u0026sup2; g⁻\u0026sup1;) and the lowest total pore volume (1.9589 m\u0026sup2; g⁻\u0026sup1;). This degradation indicates that an excessive amount of doping agents caused the collapse of the fragile pore walls and led to the agglomeration of dopants that physically blocked the pore channels. Consequently, this blockage led to limited electrolyte accessibility. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents XRD patterns of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. All samples revealed broad diffraction peaks at around 2θ\u0026thinsp;=\u0026thinsp;24\u0026deg; and 43\u0026deg;, corresponding to the (002) and (100) planes of amorphous carbon, respectively. All samples show consistent peak positions and widths which suggest that S/N co-doping does not significantly affect the activated dried pollack\u0026rsquo;s crystallinity and bring out new crystalline phases. This observation suggests that the doping process mainly influences the surface chemistry and pore structure of the activated carbon derived from dried pollack, while the overall crystallinity unchanged and no additional crystalline phases are formed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e indicate thermogravimetric analysis (TGA) and differential thermal analysis (DTA) curves. TGA and DTA were used to trace the thermal stability and compositional differences among the samples in a range of 25\u0026ndash;900\u0026deg;C in the air condition. Bare DP exhibits two major weight loss stages and 1SN-DP, 2SN-DP, and 3SN-DP exhibits three major weight loss stages. Initial loss below 100\u0026deg;C attributed to moisture and volatile impurities [18]. Around 250\u0026thinsp;~\u0026thinsp;350\u0026deg;C, 1SN-DP, 2SN-DP, and 3SN-DP exhibit major decomposition and endothermic peaks due to the decomposition of bonded surface functional groups [19]. Above 500\u0026deg;C, carbon decomposition begins, lattice rearrangement occurs due to carbon decomposition, and a strong exothermic peak appears [20]. The decomposition reaction of surface functional groups at 250\u0026thinsp;~\u0026thinsp;350\u0026deg;C indicates that surface functional groups were provided due to doping and more surface functional groups were generated as the amount of doping increased.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eX-ray photoelectron spectroscopy (XPS) analyses were conducted to clarify the chemical bonding of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a), the C 1s X-ray photoelectron spectrum shows that all samples comprise three major peaks at approximately 284.5, 286.1, and 287.1 eV, signifying C-C, C-O, and C\u0026thinsp;=\u0026thinsp;O, respectively. In particular, 1SN-DP, 2SN-DP, and 3SN-DP include two peaks related to doping at approximately 285.1 and 285.6 corresponding to C-S and C-N. 2SN-DP shows the largest peak area of C-C bonding which implies S/N co-doping promoted graphitization, forming π-π electron conduction path [21]. Notably, 3SN-DP shows smallest area of C-C, C-S, and C-N bonding among all samples. It indicates that excessive doping interrupts graphitization and heteroatoms fail to react reliably with the carbon lattice, resulting in forming defects. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b), the O 1s X-ray photoelectron spectrum presents three bonding states at ~\u0026thinsp;530.6, ~\u0026thinsp;531.5, and ~\u0026thinsp;532.9 eV, corresponding to O\u0026thinsp;=\u0026thinsp;C, HO-C, and O\u0026thinsp;=\u0026thinsp;C-C. As the amount of doping source increases, HO-C bonding peak increases and facilitates ion affinity. 3SN-DP shows an excessive amount of HO-C bonding, which means that heteroatoms such as S and N cannot enter the lattice stably and formed defects outside the framework, creating excessive functional groups disturbing electron and ion transportation. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c) exhibits that the N 1s X-ray photoelectron spectrum consist of four peaks at approximately 398.7, 399.9, 401.4, and 403.3 eV, corresponding to pyridine N, pyrrolic N, graphitic N, and oxidized N [22]. Among 1SN-DP, 2SN-DP, and 3SN-DP, 2SN-DP exhibits the largest area corresponding to the bonding state of graphitic N and pyrrolic N. Graphitic N enhances the electrical conductivity of the carbon matrix by promoting π-electron delocalization and improving structural order. Pyrrolic N contributes to the faradic redox reaction, providing additional pseudocapacitive behavior and improving ion accessibility. It enhances electron conductivity and pseudocapacitive behavior which leads to improve electrochemical performance of 2SN-DP [23]. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(d) presents that the S 2p X-ray photoelectron spectrum consist of two peaks at ~\u0026thinsp;164.1, and ~\u0026thinsp;165.2 eV, indicating C-S-C 2p\u003csup\u003e1/2\u003c/sup\u003e, and C-S-C 2p\u003csup\u003e3/2\u003c/sup\u003e, respectively. All samples exhibit two peaks, but conspicuously the 2SN-DP sample exhibits the most well-defined spin\u0026ndash;orbit doublet, with a sharp and symmetric peak shape, suggesting sulfur atoms well doped within the carbon lattice due to the optimized doping concentration [24, 25]. In contrast, the 1SN-DP and 3SN-DP show poorly resolved peaks with diminished intensity, suggesting sulfur doping is not well-formed within the carbon lattice.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, cyclic voltammetry (CV) profiles, as expected, 2SN-DP shows the largest area closest to the rectangular. The bare DP electrode exhibits distorted, non-rectangular CV curves, indicating sluggish ion transport and limited double-layer formation. Furthermore, distortion of the rectangular shape of CV curves becomes more pronounced as the scan rate increases, which implies poor rate capacity. In contrast, the 2SN-DP electrode retains semi-rectangular shape even at high scan rates, suggesting excellent rate capability and efficient ion accessibility [26, 27]. Notably, 3SN-DP electrode shows a slightly improved rectangular shape compared to the bare DP electrode, but a distorted rectangular shape compared to the 2SN-DP electrode, implying that excessive doping interrupted rapid ion diffusion and block active sites.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a), to define the charge storage mechanism, scan rate and peak current were analyzed in detail through the power law equation \u003cem\u003ei\u0026thinsp;=\u0026thinsp;a v\u003c/em\u003e\u003csup\u003e\u003cem\u003eb\u003c/em\u003e\u003c/sup\u003e. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, Log \u003cem\u003ei\u003c/em\u003e-log \u003cem\u003ev\u003c/em\u003e plots yielded b-values of 0.652, 0.769, 0.774, and 0.649 for bare DP, 1SN-DP, 2SN-DP, and 3SN-DP, respectively. The 2SN-DP sample exhibits the highest b-value (0.774), confirming its capacitive-diffusion mixed energy storage mechanism [28]. As 2SN-DP shows capacitive behavior, it retained the quasi-rectangular CV profiles even at high scan rates, confirming the ability to sustain rapid ion diffusion and efficient electronic conductivity under fast charge-discharge condition [29]. The low b-value of 3SN-DP suggests that excessive doping induces pore blockage, which lengthens effective diffusion paths and lowers accessible surface on the time scale of fast scans. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b) the Nyquist plots of the 2SN-DP electrode notably exhibited the lowest charge-transfer resistance (R\u003csub\u003ect\u003c/sub\u003e) in comparison with the Bare DP and other doped samples. This significant reduction was caused by the interactive effect of the optimized surface functionalization and pore distribution. The chemical etching during the S/N co-doping process helps to form interconnection of channels between micropores and mesopores within the carbon matrix. This well-developed porous network minimizes the resistance for electrolyte penetration, leading to the fast ion diffusion rate at the interface of electrode-electrolyte comparison with the Bare DP. Moreover, the 2SN-DP electrode showed the largest slope of the graph, indicating the most efficient ion diffusion rate in the electrolyte. This superior electrochemical behavior is derived from improved electrical conductivity resulting from the incorporation of sulfur and nitrogen heteroatoms. The doping introduces electron-rich sites into the carbon lattice, which produces extra electrons to the conduction band and induces the delocalization of electrons [30]. This modification effectively lowers the intrinsic resistance of the material, facilitating faster electron transport in the charge-storage process. Consequently, 2SN-DP demonstrated the highest electrochemical conductivity and ideal capacitive behavior among all prepared samples [31].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a-d) presents the GCD curves of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP measured at diverse current densities. All electrodes show the typical charge/discharge profiles. The 2SN-DP sample exhibited the longest discharge time due to enhanced electron conduction and ion transportation, development of uniform micro-mesopores, and increased active sites via doping. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(e) presents the specific capacitance values of all samples derived from galvanostatic charge\u0026ndash;discharge (GCD) curves. C\u003csub\u003esp\u003c/sub\u003e was derived using the following Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{C}_{sp}=\\frac{I\\:\\times\\:\\:\\varDelta\\:t}{m\\:\\times\\:\\:\\varDelta\\:V}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:\\)\u003c/span\u003e \u003c/span\u003eThe specific capacitances of the bare DP, 1SN-DP, 2SN-DP, and 3SN-DP were calculated to 127.0, 184.9, 189.5, and 161.2 F g\u003csup\u003e-1\u003c/sup\u003e at 0.2 A g\u003csup\u003e-1\u003c/sup\u003e. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the specific capacitance of all electrodes at 0.2, 0.5, 1, 2, 3, 5, 7, 10, 15, and 20 A g\u003csup\u003e-1\u003c/sup\u003e, respectively. 2SN-DP electrode performed the highest capacitance value in all section, suggesting well doped activated carbon exhibits superior high-rate performance. 3SN-DP showed the smallest specific surface area but performed better capacitance performance than bare DP. It implies that changes in pore distribution through doping also affected the electrochemical performance, in particular formation of surface functional groups and N, S doping sites significantly contributes to electrochemical performance improvement.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBET and BJH result of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSamples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e [m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eTotal pore volume\u003c/p\u003e \u003cp\u003e[P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.990] [cm\u003csup\u003e3\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eAverage pore diameter [nm]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e \u003cp\u003ePore size distribution\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003eV\u003csub\u003emicro\u003c/sub\u003e(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eV\u003csub\u003emeso\u003c/sub\u003e(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eV\u003csub\u003emacro\u003c/sub\u003e(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBare DP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2880.4\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e2.4911\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.4593\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e52.491\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e46.842\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.667\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3099.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.3223\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e2.9697\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e52.561\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e46.925\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e0.514\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3267.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.4027\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e2.9072\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e54.982\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e46.400\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e0.440\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e2597.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e\u003cb\u003e1.9589\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e3.2684\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003e\u003cb\u003e54.796\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e44.689\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e0.515\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSpecific capacitance of bare DP, 1SN-DP, 2SN-DP, and 3SN-DP\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSamples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"10\" nameend=\"c11\" namest=\"c2\"\u003e \u003cp\u003eSpecific capacitance (C\u003csub\u003esp\u003c/sub\u003e, F g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.2 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e10 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e15 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e20 A g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBare DP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e127.0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e120.8\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e114.8\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e109.6\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e105.6\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e95.2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e92.3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e84.1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003e80.7\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e184.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e182.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e172.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e164.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e158.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e148.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e140.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e128.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e114.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e108.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e189.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e182.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e172.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e166.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e162.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e154.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e151.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e144.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e132.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e128.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3SN-DP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e161.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e158.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e151.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e144.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e139.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e132.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e127.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e120.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003e112.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003e108.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, 2SN-DP was successfully synthesized by KOH activation and heteroatom doping via hydrothermal synthesis. KOH activation generated a highly mesoporous structure resulting in the largest specific surface area and doping process introduced the functional groups on surface which are favorable for high-efficient EDLCs. To determine the optimal doping ratio, the amount of doping precursor added during synthesis was adjusted to three levels, corresponding to mass ratios of bare DP to doping precursor of 1:1, 1:2, and 1:3. Optimal doping with a mass ratio of carbon-to-doping source 1:2 was applied to 2SN-DP sample, which optimally formed high specific surface area via gas-releasing decomposition during pyrolysis, which provides abundant active sites for ion adsorption, significantly facilitating the development of the electric double layer and thereby enhancing the overall energy storage capacity. Doping process also facilitated the incorporation of electrochemically active nitrogen species (graphitic N and pyrrolic N), and enhanced the surface functionalities (C-N, C-S), leading to improved electrolyte wettability and charge transfer capability. This resulted in the superior specific surface area (3267.1m\u003csup\u003e2\u003c/sup\u003e g-1), favorable pore distribution, and nearly capacitive charge storage behavior (b\u0026thinsp;\u0026asymp;\u0026thinsp;0.774). Specifically, the CV curves of 2SN-DP showed a symmetric quasi-rectangular profile typical of EDLCs, with a significantly larger CV curve area compared to Bare DP. This confirms that the heteroatom doping successfully enhanced the overall charge storage capacity which can improve specific capacitance (189.5 F g\u003csup\u003e-1\u003c/sup\u003e at a current density of 0.2 A g\u003csup\u003e-1\u003c/sup\u003e, 128.52 F g\u003csup\u003e-1\u003c/sup\u003e at 20 A g\u003csup\u003e-1\u003c/sup\u003e). In contrast, insufficient doping (1SN-DP) produced limited porosity and reduced functionalization, while excessive doping (3SN-DP) induced partial pore blockage and an increased proportion of -OH groups that hinders ion transport, shifting the charge storage toward a diffusion-controlled process. The results demonstrate that controlled heteroatom doping finely tune both the physical structure and the chemical composition of carbon materials, maximizing their electrochemical performance for energy storage applications. Thus, 2SN-DP could be an attractive active material for high performance supercapacitor.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Research Program funded by the SeoulTech (Seoul National University of Science and Technology)\u003cbr clear=\"all\"\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eW. Xu, G.Wang, S. Liu, J. Wang, W.H. Mcdaowell, K. Huang, P.A. Raymong, Z. Yang, X. Xia, Globally elevated greenhouse gas emissions from polluted urban rivers. Nat. Sustain. 7, 938\u0026ndash;948 (2024)\u003c/li\u003e\n\u003cli\u003eJ. Liu, Z. Bao, Y. Cui, E.J. Dufek, J.B. Goodenough, P. Khalifah, Q. Li, B.Y. Liaw, P. Liu, A. Manthiram, Y.S. Meng, V.R. Subramanian, M.F. Toney, V.V. Viswanathan, M.S. Whittingham, J. Xiao, W. Xu, J. Yang, X.Q. Yang, J.G. Zhang, Pathways for practical high-energy long-cycling lithium metal batteries. Nat. Energy 4, 180\u0026ndash;186 (2019)\u003c/li\u003e\n\u003cli\u003eX. Tian, X. Zhao, Y.Q. Su, L. Wang, H. Wang, D. Dang, B. Chi, H, Liu, E.J.M. Hensen, X.W. Lou, B.Y. Xia, Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells. Electrochemistry 366, 6467 (2019)\u003c/li\u003e\n\u003cli\u003eG Xu, J. Han, B. Ding, P. Nie, J, Pan, H. Dou, H. Li, X. Zhang, Biomass-derived porous carbon materials with sulfur and nitrogen dual-doping for energy storage. Green Chem. 17, 1668 (2015)\u003c/li\u003e\n\u003cli\u003eG.-H. An, S.-N. Cha, H.-J. Ahn, Surface functionalization of the terraced surface-based current collector for a supercapacitor with an improved energy storage performance. Appl. Surf. Sci. 478, 435\u0026ndash;440 (2019)\u003c/li\u003e\n\u003cli\u003eJ. Zhang, Y.L. Xie, Hierarchical porous hollow of carbon spheres with high surface area for high performance supercapacitor electrode materials. Sci Rep 15, 15125 (2025)\u003c/li\u003e\n\u003cli\u003eG. Zhong, S. Xu, J. Chao, X. Fu, W. Liao, Y. Xu, Z. Liu, Y. Cao, Biomass derived nitrogen-doped porous carbons activated by magnesium chloride as ultrahigh performance supercapacitors. Ind. Eng. Chem. Res. 59, 21756\u0026ndash;21767 (2020)\u003c/li\u003e\n\u003cli\u003eM.-H. Jo, H.-J. Yoon, H.-J. Ahn, Pre‑nitrogen doping effects on mesoporous activated carbon derived from passiflora edulis for high‑performance supercapacitors. Korean J. Chem. Eng. 43, 337\u0026ndash;349 (2026)\u003c/li\u003e\n\u003cli\u003eK.-H. Kim, Y.-J. Song, H.-J. Ahn, N-doped mesoporous activated carbon derived from protein-rich biomass. Korean J. Chem. Eng. 40, 1071\u0026ndash;1076 (2023) for energy storage applications\u003c/li\u003e\n\u003cli\u003eW. Chen, M. Gong, K. Li, M. Xia, Z. Chen, H. Xiao, Y. Fang, Y. Chen, H. Yang, H. Chen, Insight into KOH activation mechanism during biomass pyrolysis: chemical reactions between O-containing groups and KOH. Appl. Energy 278, 115730 (2020)\u003c/li\u003e\n\u003cli\u003eD. Guo, Z. Li, P. Liu, M. Sun, N, P, S co-doped biomass-derived hierarchical porous carbon through simple phosphoric acid assisted activation for high-performance electrochemical energy storage. Int. J. Hydrog. Energy 46, 8197\u0026ndash;8209 (2021)\u003c/li\u003e\n\u003cli\u003eJ. Wang, T. Huo, Y. Zhao, R. Lu, X. Wu, Recent advances in heteroatoms-doped porous carbon electrode materials for supercapacitors: A review. J. Energy Storage 110, 115216 (2025)\u003c/li\u003e\n\u003cli\u003eD. Wang, H. Dong, D. Zhang, C. Wang, K. Lu, M. Shi, G. Tong, In-situ template-assisted self-activation craft for direct preparing mesoporous-dominated N/S co-doped hierarchical porous carbon for supercapacitors. Int. J. Biol. Macromol. 305, 141361 (2025)\u003c/li\u003e\n\u003cli\u003eH. Rustamaji, T. Prakoso, H. Devianto, P. Widiatmoko, K.A. Kurnia, Facile synthesis of N, S-modified activated carbon from biomass residue for promising supercapacitor electrode applications. Bioresour. Technol. Rep 21, 101301 (2023)\u003c/li\u003e\n\u003cli\u003eY. Yardim, I. Genel, C. Saka, Enhanced supercapacitor performance of hierarchical mesoporous sulfur-doped carbon particles from biomass waste for energy storage. Int. J. Hydrog. Energy 99, 383\u0026ndash;393 (2025)\u003c/li\u003e\n\u003cli\u003eJ. Han, Q. Li, C. Peng, N. Shu, F. Pan, J. Wang, Y. Zhu, Increasing S dopant and specific surface area of N/S-codoped porous carbon y in-situ polymerization of PEDOT into biomass precursor for high performance supercapacitor. Appl. Surf. Sci. 502, 144191 (2020)\u003c/li\u003e\n\u003cli\u003eM. Jiang, X. Yu, R. Gao, T. Yang, Z. Xu, L. Cao, Fabrication of biomass-derived N, S co-doped carbon with hierarchically porous architecture for high performance supercapacitor. Nano 15, 2050096 (2020)\u003c/li\u003e\n\u003cli\u003eO. Zanella, D. Bilibio, W.L. Priamo, Porous structure and characterization of activated carbons from the grape stalks. SusProc. 1, 138473 (2025)\u003c/li\u003e\n\u003cli\u003eJ. Zhang, S. Li, B. Tang, Z. Wang, G. Ji, W. Huang, J. Wang, High photocatalytic performance of two types of graphene modified TiO\u003csub\u003e2\u003c/sub\u003e composite photocatalysts. Nano Express 12, 457 (2017)\u003c/li\u003e\n\u003cli\u003eH. Liu, Y. Zhang, R. Li, X. Sun, H. Abou-Rachid, Thermal and chemical durability of nitrogen-doped carbon nanotubes. J. Nanopart. Res. 14, 1016 (2012)\u003c/li\u003e\n\u003cli\u003eH. Jia, J. Sun, X. Xie, K. Yin, L. Sun, Cicada slough-derived heteroatom incorporated porous carbon for supercapacitor: ultra-high gravimetric capacitance. Carbon 143, 309\u0026ndash;317 (2029)\u003c/li\u003e\n\u003cli\u003eC.-Y. Lee, H.-J. Ahn, Electrochemical performance of reduced graphyne oxide and biomass-derived activated carbon composite for energy storage devices. J. Porous Mat. 32, 1519\u0026ndash;1530 (2025)\u003c/li\u003e\n\u003cli\u003eL. Ji, B. Wang, Y. Yu, N. Wang, J. Zhao, N, S co-doped biomass derived carbon with sheet-like microstructures for supercapacitors. Electrochim. Acta 331, 135348 (2020)\u003c/li\u003e\n\u003cli\u003eV. Thirumal, T.V.M. Sreekanth, K.-S. Yoo, J.-H. Kim. Biomass-derived hard carbon and nitrogen-sulfur co-doped graphene for high-performance symmetric sodium ion capacitor devices. Energies 16, 802 (2023)\u003c/li\u003e\n\u003cli\u003eY. Li, G. Wang, T. Wei, Z. Fan, P. Yen, Nitrogen and sulfur co-doped porous carbon nanosheets derived from willow catkin for supercapacitors. Nano Energy 19, 165\u0026ndash;175 (2016)\u003c/li\u003e\n\u003cli\u003eA. Borenstein, O. Hanna, R. Attias, S. Luski, T. Brousse, D. Aurbach, Carbon based composite materials for supercapacitor electrodes: a review. J. Mater. Chem. A 5, 12653 (2017) \u003c/li\u003e\n\u003cli\u003eR. Dev, H. Gupta, H. Gahtori, H.K. Rathore, M. Hariram, M. Kumar, P.W. Menezes, D. Sarkar, Sustainable activated carbon for aqueous and flexible zinc-ion energy storage. Carbon 245, 120762 (2025) \u003c/li\u003e\n\u003cli\u003eJ. Qi, C. Zhang, M. Huang, M. Zhang, T. Li, M. Shi, Z. Wei, J, Ni, Q. Li, Y. Sui, Q. Meng, B. Xiao, F. Wei, L. Zhu, R. Shao, Defect engineering of porous carbon with high N/S doping for potassium ion storage. Appl. Surf. Sci. 657, 159771 (2024)\u003c/li\u003e\n\u003cli\u003eY. Liao, Z. Shang, G. Ju, D. Wang, Q Yang, Y. Wang, S. Yuan, Biomass derived N-doped porous carbon made from reed straw for an enhanced supercapacitor. Molecules 28, 4633 (2023)\u003c/li\u003e\n\u003cli\u003eG. Zhao, Y. Li, G. Zhu, J. Shi, T. Lu, L. Pan, Biomass-based N, P, and S self-doped porous carbon for high-performance supercapacitors. ACS Sustain. Chem. Eng. 7, 12052\u0026ndash;12060 (2019)\u003c/li\u003e\n\u003cli\u003eX. Yang, X. Wang, B. Lu, B. Huang, Y. Xia, G. Lin, Biomass-derived N, S co-doped activated carbon-polyaniline nanorod composite electrodes for high-performance supercapacitors. Appl. Surf. Sci. 639, 158191 (2023)\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"korean-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"kjce","sideBox":"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)","snPcode":"11814","submissionUrl":"https://www.editorialmanager.com/kjce/default2.aspx","title":"Korean Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Subscription","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9164790/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9164790/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBiomass derived activated carbon has been emerged as alternatives to the depletable resources due to its sustainability and low cost. Large surface area and the optimal pore distribution of micropores, mesopores, and macropores are crucial for achieving high performance activated carbon. Thereby, we synthesized KOH activated carbon derived from protein-rich dried pollack which exhibits mesoporous structure with high surface area. We improved the electrolyte wettability and charge transfer capability by performing a doping process to introduce electrochemically active nitrogen species (graphitic N and pyrrolic N) and functional groups forming surface functionalities (C-N, C-S). 2SN-DP electrode shows the largest specific surface area (2764.8 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e), favorable pore distribution, nearly capacitive charge storage behavior (b\u0026thinsp;\u0026asymp;\u0026thinsp;0.774), and superior specific capacitance (189.5 F g\u003csup\u003e-1\u003c/sup\u003e at a current density of 0.2 A g\u003csup\u003e-1\u003c/sup\u003e and 128.52 F g\u003csup\u003e-1\u003c/sup\u003e at 20 A g\u003csup\u003e-1\u003c/sup\u003e). The outstanding performance of 2SN-DP electrode was attributed to the interactive effects of improved ion transportation and conductivity provided by KOH activation and N/S co-doping.\u003c/p\u003e","manuscriptTitle":"S/N Co-Doped Activated Mesoporous Carbon derived from Protein-Rich Dried Pollock for Supercapacitor","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-30 15:57:45","doi":"10.21203/rs.3.rs-9164790/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-03-27T01:12:23+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-27T01:11:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-25T12:59:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Korean Journal of Chemical Engineering","date":"2026-03-19T00:23:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"korean-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"kjce","sideBox":"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)","snPcode":"11814","submissionUrl":"https://www.editorialmanager.com/kjce/default2.aspx","title":"Korean Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Subscription","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"55e199c4-0c6f-40ca-a5a9-b4f9a88e53b9","owner":[],"postedDate":"March 30th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-18T03:25:53+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-30 15:57:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9164790","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9164790","identity":"rs-9164790","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}