Nitrogen-doped Activated Carbon Research Articles

WO3 Nanoparticle/Biomass Derived N‐Doped Activated Carbon Decorated with Polyaniline Nanofibers Ternary Nanocomposite for High‐Performance Symmetric and Asymmetric Supercapacitor

AbstractSupercapacitors have captured the curiosity of researchers due to their extremely high energy storage capacity. Hybrid supercapacitors deliver high specific capacitance values compared to the exciting (electrical double layer capacitor) EDLC and pseudocapacitors. This work presents a simple and scalable synthetic method to design a hybrid ternary composite as electrode material. In this work, the combination of EDLC‐type behaviour material, i. e., sustainable biomass‐derived Nitrogen‐doped activated carbon (NAC) and pseudocapacitive behaviour electrode materials, i. e., metal oxides (tungsten oxide) and conductive polymer (polyaniline) are selected to achieve a high gravimetric capacity. The PANi/WO3/NAC (PWNAC) ternary composite is tested for symmetric and asymmetric supercapacitor (ASC). In a symmetric capacitor, PWNAC acts as both the positive and negative electrode, whereas in ASC, PWNAC acts as the positive electrode and NAC as the negative electrode. It is observed that the ASC shows a better capacitance value than symmetric. ASC operates at a potential range of 1.4 V in 1 M H2SO4 aqueous electrolyte, shows a maximum capacitance of 608.2 F/g at 0.5 A/g, and has long capacitance retention of 98.32 % of its initial capacitance after 2000 charge‐discharge cycles.

Unprecedented 100% conversion from pyridinic to pyrrolic nitrogen configuration for electrochemically active nitrogen-doped carbon materials

Nitrogen-doped carbons with promising electrochemical performance exhibit a strong dependence on nitrogen configuration. Therefore, accurate control of nitrogen configurations is crucial to clarify their influence. Unfortunately, there is still no well-defined conversion route to finely control nitrogen configuration. Herein, we proposed the concept of 100% conversion from pyridinic to pyrrolic nitrogen in carbon materials through low-temperature pyrolysis and alkali activation of hydroxypyridine-3-halophenol-formaldehyde resins. Their dehalogenation pyrolysis promotes formation of carbon intermediates and conversion of tautomeric pyridone and hydroxypyridine into pyrrolic and pyridinic nitrogen through eliminating carbonyl and hydroxyl functionalities, respectively. Continuous thermal alkali activation introduces hydroxyl groups into carbon materials, converting pyridinic species to intermediate hydroxypyridine and pyridone; subsequently, these configurations transform to pyridinic and pyrrolic nitrogen, respectively, and finally, an excessive alkali ensures 100% conversion from pyridinic to pyrrolic nitrogen. NaOH activation for pyrrolic and pyridinic nitrogen co-doped carbon and KOH activation for model nitrogen-containing compounds including acridine, phenanthridine, and acridone further confirm that alkali activation plays an indispensable role in 100% conversion from pyridinic to pyrrolic units through the tautomeric hydroxypyridine and pyridone intermediates. Low-temperature alkali-induced controllable conversion of nitrogen configuration in carbon materials is suitable modulating nitrogen configurations for almost all nitrogen-doped carbon materials in electrochemical applications.

Preparation of nitrogen-doped activated carbon from bio-oil residue for efficient CO2 adsorption

An efficient strategy for the resourcezation of waste bio-oil residue was developed to fabricate nitrogen-doped activated carbon (NAC) as CO2 adsorbent. The NAC was produced by in-situ nitrogen-doped carbonization and K2CO3 activation, using urea as nitrogen source. The effects of activation temperature, mass ratios of urea to bio-oil residue (U/O ratio) and K2CO3 to char (K/C ratio) on the physicochemical properties and CO2 adsorption performance of NAC were investigated. Under the conditions of activation temperature of 750 °C, U/O ratio of 1 and K/C ratio of 3, the as-prepared NAC exhibited the greatest CO2 adsorption performance with an excellent CO2 adsorption capacity of 6.22 mmol/g at 1 bar and 0 °C, which was much higher than that without nitrogen doping (2.21 mmol/g). In addition, the CO2/N2 selectivity of NAC was 14.3 and the adsorption capacity loss was below 1% after 5 consecutive cycles, revealing promising potentials in carbon capture applications.

Biomass-based nitrogen-doped carbon/polyaniline composite as electrode material for supercapacitor devices

Nitrogen-doped activated carbon (N-AC) was prepared from water hyacinth stems for loading polyaniline (PANI) by in-situ polymerization to synthesize N-AC/PANI composites for utilization as electrode materials in supercapacitors. Using potassium hydroxide as the activating agent, stems of water hyacinth were carbonized and activated in a single step to produce N-AC powders. Raman, FTIR, SEM, BET, TGA, and XPS techniques were used to characterize the resultant N-AC materials. The findings revealed that the N-AC materials had a porous structure and high specific surface area. Neat PANI was synthesized by varying the reaction time to 8, 16, and 24 h. During the reaction time of 16 h, the maximum specific capacitance was obtained. For the synthesis of N-AC/PANI composites, in-situ polymerization of aniline was performed for 16 h. Tests of cyclic voltammetry and galvanostatic charge/ discharge were conducted on the electrode materials to assess their electrochemical performance for supercapacitors. Because of the synergistic effect of PANI and N-AC, the produced N-AC/PANI composite showed good supercapacitor performance compared with neat PANI and N-AC. In the case of the N-AC/PANI composite, the specific capacitance was determined by the electrochemical double-layer capacitance (EDLC) of N-AC and the pseudocapacitance resulting from the redox reaction of PANI.

A Review on Hydrogen Generation by Photo-, Electro-, and Photoelectro-Catalysts Based on Chitosan, Chitin, Cellulose, and Carbon Materials Obtained from These Biopolymers

Biopolymer-based catalysts like chitosan, chitin, and cellulose offer sustainability and high efficiency both as the catalyst or catalyst support in a broad range of applications, especially in hydrogen evolution reactions. This review focused on hydrogen evolution catalysts of chitosan, chitin, cellulose, and carbon materials obtained from these biopolymers to highlight the opportunities of these sustainable catalysts in this field. All the reports in this area could be classified as one of the photocatalysts, electrocatalysts, and photoelectrocatalysts, and their mechanisms were clarified in the beginning. Then, the results of catalysts obtained from each of these biopolymers were discussed separately to reveal the roles of the biopolymers. It was concluded that all of the biopolymers enjoy some common benefits like hydrogen bonding, chelating with transition metals, easy chemical modification, high performance, and potential to be used as the precursors of carbon or porous materials. Among them, chitosan showed outstanding merit due to the better performance in metal grafting, amendment, and ability of hydrogen bonding. Moreover, it provides highly active nitrogen-doped carbon as the support of transition metals in the hydrogen generation, enhancing the reaction rate by retarding the charges recombination.

Synthesis of aromatic monomers via hydrogenolysis of lignin over nickel catalyst supported on nitrogen-doped carbon nanotubes

The utilization of lignin to produce high value-added chemicals remains a significant challenge, this study reports the synthesis of highly active nitrogen-doped carbon nanotubes to support nickel-based catalysts via a two-stage pyrolysis process using a mixture of melamine and nickel acetate. The catalyst morphology is controlled through the use of melamine, the doped pyridinic nitrogen serves as an anchoring site for Ni metal, facilitating the dispersion of Ni metal and the formed Ni-Nx bond enhanced the stability of the catalyst. Additionally, the electron transfer between Ni and N atoms promoting the activation of hydrogen on the metallic nickel surface, which together with the aforementioned factors, contributes to the cleavage of the C-O bond in lignin, with 23.1% monomer yield under mild conditions. The density functional theory (DFT) calculations reveal that doped nitrogen atoms can provide electrons to carbon atoms, resulting in an electron-rich state that facilitated the adsorption of hydrogen.

Melamine assisted preparation of nitrogen doped activated carbon from sustainable biomass for H2 and CO2 storage

Activated carbon (AC), as an effective solid adsorbent, is extensively employed in H2 and CO2 storage. To enhance its adsorption capability and selectivity, it is necessary to increase its surface area and dope heteroatoms by a simple and environment-friendly method. In this work, nitrogen doped activated carbon (NAC) has been synthesized from sustainable biomass by direct activation with the assistance of melamine. The obtained NAC with 2.1 wt% N dopants possesses a high surface area (2477.27 m2/g) and pore volume (1.93 cm3/g). The NAC displayed enhanced H2 uptake capacity (2.29 wt% at 77 K, 1 bar and 0.83 wt% at 298 K, 100 bar) and adequate CO2 uptake capacity (2.85 mmol/g at 298 K, 1 bar and 4.49 mmol/g at 273 K, 1 bar). Activation mechanism with the assistance of melamine was proposed in accordance with the experimental data. The facile method of preparing NAC is potential for large-scaled production.

Biomass valorisation of marula nutshell waste into nitrogen-doped activated carbon for use in high performance supercapacitors

This study reports on the valorisation of marula nutshell waste into a valuable electrode material for supercapacitors. Marula nutshell waste, a brown hard residue from marula fruits was valorised into a nitrogen-doped activated carbon (N-ACs) by KOH treatment and using melamine as a nitrogen source. The microporous and mesoporous nature of N-ACs exhibited a high surface area of 1427 m² g−1 and pore volume of 0.31 cm3 g−1. Three electrode measurements were done in 6 M KOH and 2.5 M KNO3 aqueous electrolytes, to examine the materials in alkaline and neutral medium. The N-ACs exhibited a capacitance of 350 F g−1 in 6 M KOH and 248 F g−1 in 2.5 M KNO3 electrolyte. Due to low toxicity and wider operating voltage (∼1.8 V) of 2.5 KNO3, the material was further analysed in a symmetric device. The high surface area, the defects, and the high content of nitrogen (5.1%) revealed that the material produced an outstanding energy density of 17.2 Wh kg−1 and a power density of 448.7 W kg−1 in 2.5 M KNO3 electrolyte. The conversion of marula nuts waste into N-ACs thus provide a means of converting biomass waste into a useful energy storage material for supercapacitors.

Ultrastable Fe-N-C Fuel Cell Electrocatalysts by Eliminating Non-Coordinating Nitrogen and Regulating Coordination Structures at High Temperatures.

Pyrolyzed Fe-N-C materials have attracted considerable interest as one of the most active noble-metal-free electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Despite significant progress is made in improving their catalytic activity during past decades, the Fe-N-C catalysts still suffer from fairly poor electrochemical and storage stability, which greatly hurdles their practical application. Here, an effective strategy is developed to greatly improve their catalytic stability in PEMFCs and storage stability by virtue of previously unexplored high-temperature synthetic chemistry between 1100 and 1200°C. Pyrolysis at this rarely adopted temperature range not only enables the elimination of less active nitrogen-doped carbon sites that generate detrimental peroxide byproduct but also regulates the coordination structure of Fe-N-C from less stable D1 (O-FeN4 C12 ) to a more stable D2 structure (FeN4 C10 ). The optimized Fe-N-C catalyst exhibits excellent stability in PEMFCs (>80% performance retention after 30h under H2 /O2 condition) and no activity loss after 35 day storage while maintaining a competitive ORR activity and PEMFC performance.

Electrospun MnCo2O4/carbon-nanofibers as oxygen electrode for alkaline zinc-air batteries

A MnCo2O4 catalyst supported on nitrogen-doped carbon nanofibers (CNF) obtained in a single-step electrospinning process is presented. MnCo2O4/CNF is investigated as bifunctional electrode for the electrocatalysis of oxygen in metal-air batteries. Crystallographic structure, morphology, and surface properties are analyzed using solid-state characterization techniques that reveal the presence of a 20 nm-particle-sized spinel and a large amount of oxidized metal species (Mn4+ and Co3+). These features are correlated with the electrochemical behavior for the oxygen reduction (ORR) and oxygen evolution (OER), showing good performances in particular for the OER compared with IrO2, benchmark catalyst for this reaction. Results revealed a synergistic effect of the catalytically active nitrogen-doped carbon nanofiber and the manganese and cobalt active species from the spinel, being responsible for the remarkable reversibility of this catalyst (ΔE = 799 mV), outperforming most of the previous works in the literature on this type of manganese/cobalt-based spinel materials. A preliminary test of an alkaline Zn-air battery equipped with this catalyst at the oxygen (positive) electrode confirms proper activity and stability during cycling operations typical of these rechargeable devices. Besides, the spinel-nanofiber-based catalyst has been produced by an easily-scalable electrospinning process, representing an advance of the current technology on positive electrodes for metal-air batteries. The curated synthesis of our MnCo-N-CNF spinel is fundamental to obtaining a catalyst with a high intrinsic catalytic activity (determined by rotating disk electrode) and an appropriate performance in a relevant environment (both gas diffusion electrode and Zn-air battery).

Optimized Lithography-Free Fabrication of Sub-100 nm Nb2O5 Nanotube Films as Negative Supercapacitor Electrodes: Tuned Oxygen Vacancies and Cationic Intercalation.

The direct growth of sub-100 nm thin-film metal oxides has witnessed a sustained interest as a superlative approach for the fabrication of smart energy storage platforms. Herein, sub-100 nm Zr-doped orthorhombic Nb2O5 nanotube films are synthesized directly on the Nb-Zr substrate and tested as negative supercapacitor electrode materials. To boost the pseudocapacitive performance of the fabricated films, supplement Nb4+ active sites (defects) are subtly induced into the metal oxide lattice, resulting in 13% improvement in the diffusion current at 100 m V/s over that of the defect-free counterpart. The defective sub-100 nm film (H-NbZr) exhibits areal and volumetric capacitances of 6.8 mF/cm2 and 758.3 F/cm3, respectively. The presence of oxygen-deficient states enhances the intrinsic conductivity of the thin film, resulting in a reduction in the band gap energy from 3.25 to 2.5 eV. The assembled supercapacitor device made of nitrogen-doped activated carbon (N-AC) and H-NbZr (N-AC//H-NbZr) is able to retain 93, 83, 78, and 66% of its first cycle capacitance after 1000, 2000, 3000, and 4500 successive charge/discharge cycles, respectively. An eminent energy record of approximately 0.77 μW h/cm2 at a power of 0.9 mW/cm2 is achieved at 1 mA/cm2 with superb capability.

Exploring the electrochemical behavior of Mo1.33CTz MXene in aqueous sulfates electrolytes: Effect of intercalating cations on the stored charge

MXenes have been introduced as a high energy and power density electrochemical supercapacitor material owing to their high specific capacitance and electrochemical stability. The operating potential window and, in turn, energy density of MXene based symmetric and asymmetric supercapacitors can be effectively enhanced by the proper choice of aqueous electrolyte. Herein, we investigate the electrochemical behavior of vacancy-containing i-MXene (Mo1.33CTz) in sulfate based aqueous electrolytes with univalent (Li+, Na+, or K+) or divalent (Mg2+, Mn2+, or Zn2+) cations. The results show that the Mo1.33CTz MXene electrodes can be operated in a potential window higher than 1 V without degradation in these sulfate electrolytes. The Mo1.33CTz MXene electrodes deliver a high volumetric capacitance up to ∼677 F cm−3 as measured in 1.0 M MnSO4 solution. Furthermore, symmetric (Mo1.33CTz//Mo1.33CTz) and asymmetric (Mo1.33CTz//nitrogen-doped activated carbon (NAC)) devices in 0.5 M K2SO4 solution can be operated with a cell voltage of about 1.1 V and 1.8 V, respectively. The asymmetric devices retain about 97% of their initial capacitance after 5000 charge/discharge cycles. Overall, the results reveal that the choice of the intercalating cations is a viable route to boost the performance of Mo1.33CTz MXene and to construct energy storage devices.

SnO2/SnS2 heterostructure@ MXene framework as high performance anodes for hybrid lithium-ion capacitors

Among all kinds of energy storage devices, lithium-ion capacitors (LICs) emerged victorious because of their advantages of high energy densities and power densities. The main issue that limits the performance of LICs is the mismatch in reaction kinetics caused by the disparate energy storage mechanisms of the positive and negative materials. Herein, a Sn-based heterostructure@MXene anode material was synthesized to achieve excellent rate performance and to increase the lithium storage capacity, which enables a good match with the cathode. In the synthesized hybrid electrode, the heterostructure can regulate the charge transmission at interfaces and improve the kinetics of electron conduction and ion diffusion. Meanwhile, the highly conductive MXene can buffer the large volumetric change of SnS2/SnO2 nanoparticles, and synergically improve electrochemical properties of the hybrid electrode. The hybrid electrode exhibited remarkable rate performance and cycle stability, showing 619 mAh g−1 at 0.5 A g−1 after 200 cycles, which greatly reduced the kinetic gap with capacitor-type cathodes. The assembled LICs based on the SnS2/SnO2@MXene hybrid anode and nitrogen-doped activated carbon (N-AC) cathode offer a high power/energy density (maximum 11.25 kW kg−1 and 145.2 Wh kg−1) and a long cycling life (93.6% capacity retention after 2000 discharges/charges). This unique structure and the composition design provide a promising path for the fast kinetic LICs anode materials.

Interface Engineering on Cellulose-Based Flexible Electrode Enables High Mass Loading Wearable Supercapacitor with Ultrahigh Capacitance and Energy Density.

For practical energy storage devices, a bottleneck is to retain decent integrated performances while increasing the mass loading of active materials to the commercial level, which highlights an urgent need for novel electrode structure design strategies. Here, an active nitrogen-doped carbon interface with "high conductivity, high porosity, and high electrolyte affinity" on a flexible cellulose electrode surface is engineered to accommodate 1D active materials. The high conductivity of interface favors fast electron transport, while its high porosity and high electrolyte affinity properties benefit ion migration. As a result, the flexible anode accommodated by carbon nanotubes achieves an ultrahigh capacitance of 9501 mF cm-2 (315.6 F g-1 ) at a high mass loading of 30.1mg cm-2 , and the flexible cathode accommodated by polypyrrole nanotubes realizes a remarkably high capacitance of 6212 mF cm-2 (248 F g-1 , 25mg cm-2 ). The assembled flexible quasi-solid-state asymmetric supercapacitor delivers a maximum energy density of 1.42 mWh cm-2 (2.2V, 2105 mF cm-2 ), representing the highest value among all reported flexible supercapacitors. This versatile design concept provides a new way to prepare high performance flexible energy storage devices.

A high-performance asymmetric supercapacitor achieved by surface-regulated MnO2 and organic-framework–derived N-doped carbon cloth

It is possible to achieve high energy density and power density simultaneously for asymmetric supercapacitors by using pseudocapacitive materials with abundant ion intercalation/de-intercalation sites on the surface. Herein, a positive electrode based on feather-like MnO2 anchored on the activated carbon cloth is prepared, in which oxygen-enriched MnO2 nanorods with a radial sheet-like structure (OMO@AC) further form via electrochemical oxidation. Because of the large contact area with electrolyte and abundant oxidation functional groups on its surface, the OMO@AC displays excellent capacitance of 3,160 mF/cm2 at 1 mA/cm2. For the nitrogen-doped active carbon negative electrode, the capacitance is up to 1,875 mF/cm2 at 4 mA/cm2 due to the increase in disorder and defect on the carbon surface by N-doping. Furthermore, we verify the good electrochemical activity on the OMO@AC electrode surface by first-principles calculations and confirm the good matching degree between the positive and negative electrodes by CV testes. The aqueous oxygen-enriched MnO2// nitrogen-doped active carbon asymmetric supercapacitor exhibits an ultrahigh energy density of 8.723 mWh/cm3 at a power density of 14.248 mW/cm3 and display excellent cycle stability maintaining 95.5% after 10,000 cycles. The facile synthesis method and excellent performance provide a feasible way for the preparation of high-performance electrode materials for energy storage devices.

A high-temperature anion-exchange membrane fuel cell with a critical raw material-free cathode

We present a first high-temperature anion-exchange membrane fuel cell (HT-AEMFC, operating at 105 °C) based on a critical raw material (CRM)-free cathode catalyst; at the same temperature, the anion-exchange membrane (AEM) has a high ex-situ hydroxide conductivity value of 201 mS cm−1. Our HT-AEMFC, containing a highly active nitrogen-doped carbon (N-doped-C) cathode catalyst, also features low polarization resistances, high catalytic activity and stability, with retention of 81% of the catalyst layer capacitance after an initial 10 h longevity test, and delivery of a peak power of 1.14 W cm−2. This is one of the highest power densities reported for an AEMFC containing a CRM-free cathode. This work shows the potential of the new field of HT-AEMFCs, opening opportunities for developing and using novel CRM-free catalysts that are highly active at these high operating temperatures.

Efficient light-free activation of peroxymonosulfate by carbon ring conjugated carbon nitride for elimination of organic pollutants

Realizing graphitic carbon nitride (g-C3N4) being active in light-free heterogeneous catalysis remains a big challenge as a result of its inertness if not irradiated. Herein, we demonstrate the successful construction of g-C3N4-based in-plane heterostructure by intimately connecting g-C3N4 framework with carbon ring via strong π-conjugated bonds, which regulates the electron density distribution of the g-C3N4 composite. The optimized carbon ring conjugated carbon nitride (CCN0.1) with porous architecture and modulated electronic structure delivers admirable catalytic performance in peroxymonosulfate (PMS) activation without the need of light, with its specific activity being significantly superior to nonmetal-doped g-C3N4 and comparable to part of active nitrogen-doped carbon materials. Experimental data and theoretical results revealed the two domains of g-C3N4 with higher electron density and the conjugated carbon ring with lower electron density in CCN0.1 involve in PMS conversion accounting for PMS reduction and oxidation, respectively, which simultaneously facilitates dissolved oxygen reduction over the g-C3N4 field. Moreover, CCN0.1 shows robust stability in PMS activation, and meanwhile, the CCN0.1/PMS system exhibits potential effectiveness in actual industrial wastewater remediation. This work expands the range of nonmetallic g-C3N4-based materials for light-free activation of persulfate and deepens the mechanistic understanding of persulfate conversion process for wider environmental applications.

Preparation of porous nitrogen-doped activated carbon derived from rice straw for high-performance supercapacitor application

Environmental-friendly and low-cost biomass-derived materials have been attracted many attentions to produce porous activated carbon (AC) with high surface area for supercapacitor (SC) application. In this study, rice straw (RS), an agricultural waste, is used to prepare ACs with a two-step process of carbonization and KOH activation. As-produced AC has a high specific surface area (SSA) of 2651 m2g-1 with hierarchical pore structure. In order to enhance the performance of SC, nitrogen-doping strategy is carried out to increase nitrogen functional groups in the AC using melamine as a precursor. The SSA of the nitrogen-doped AC is 2537 m2g-1 and the capacitance of 324 F/g is achieved using nitrogen-doped AC at a current density of 0.5 Ag-1 in 6 M KOH aqueous electrolyte. The capacitance retention is 95% after 10,000 charge and discharge cycles at a current density of 5.0 Ag-1. In addition, ionic liquid is employed as the electrolyte for the supercapacitor. The energy density of 48.9 Wh/kg at a power density of 750 W/kg can be achieved using EMI-TFSI electrolyte. We think that the proposed method can be used for a variety of biomass for preparation of ACs with high specific surface area and nitrogen functional groups for the energy storage applications.

A high energy flexible symmetric supercapacitor fabricated using N-doped activated carbon derived from palm flowers.

Nitrogen doped activated carbons of high surface area are synthesized using palm flower biomaterial by KOH activation followed by pyrolysis. The concentration of the activating agent KOH and carbonization temperature are found to be crucial to obtain high surface area activated carbon. The optimal concentration of KOH and carbonization temperature for the synthesis of activated carbon, respectively, are 2 M and 800 °C in the flow of nitrogen gas. The optimized conditions have been employed to further prepare nitrogen doped activated carbon (NAC) by varying the weight ratio of palm flowers to melamine. All activated carbons are characterized by powder XRD, BET analysis, RAMAN spectroscopy, HR-SEM analysis, HR-TEM analysis and FT-IR analysis. With 2 wt% nitrogen doping, the BET surface area and pore diameter of the NAC-2 sample are 1054 m2 g−1 and 1.9 nm, respectively. The electrochemical charge storage performance of the nitrogen doped activated carbons has been evaluated in an aqueous acidic electrolyte medium. The results indicate that among the nitrogen doped activated carbons, the NAC-2 sample exhibits the highest electrochemical capacitance of 296 F g−1 at 0.5 A g−1. The performance of the NAC-2 electrode is further tested in aqueous, ionic liquid and solid polymer electrolytes by assembling a symmetric capacitor for real time application. By employing an ionic liquid as the electrolyte, the device delivers an energy density of 8.6 Wh kg−1 and a power density of 38.9 W kg−1 in the voltage window of 1.5 V and at an operating current density of 0.1 A g−1. Interestingly, the NAC-2 electrode shows good cycling performance in the ionic liquid electrolyte (up to 50k cycles). Furthermore, the symmetric device in 0.1 M H2SO4/PVA solid state electrolyte shows excellent electrochemical stability under various bending angles, demonstrating its potential in flexible electronic devices.

Preparation of activated carbon derived from oil palm empty fruit bunches and its modification by nitrogen doping for supercapacitors

Activated carbon (AC) is one of the most promising active materials for high-performance supercapacitors (SCs) owing to its high specific surface area and theoretical specific capacity. In this study, oil palm empty fruit bunches (EFBs), which are agricultural residue, are employed as a precursor to produce AC using a series of cleaning, carbonization, and chemical activation processes. The as-produced AC has a specific surface area of 2774 m2/g, which is very high among AC produced from biomass materials. To enhance the performance of SCs, the AC is modified by nitrogen doping. The specific capacities of AC and nitrogen-doped AC are found to be 182 to 217 F/g, respectively, at a current density of 0.5 A/g in 6 M KOH aqueous electrolyte. We demonstrate that agricultural waste can be processed into AC with a high specific surface area for SC applications.