Search Results (32)

The development of cost-effective and scalable air/oxygen electrode materials is crucial for the advancement of Zn–air batteries (ZABs). Porous carbon materials doped with heteroatoms have attracted considerable attention in energy and environmental fields because of their tunable nanoporosity and high electrical conductivity. In this work, we report the synthesis of a three-dimensional (3D) N and P co-doped porous carbon (PA@pDC-1000), derived from a conjugated polyaniline–phytic acid polymer. The cross-linked, rigid conjugated polymeric framework plays a crucial role in maintaining the integrity of micro- and mesoporous structures and promoting graphitization during carbonization. As a result, the material exhibits a hierarchical pore structure, a high specific surface area (1045 m² g⁻¹), and a large pore volume (1.02 cm³ g⁻¹). The 3D N, P co-doped PA@pDC-1000 catalyst delivers a half-wave potential of 0.80 V (vs. RHE) and demonstrates a higher current density compared to commercial Pt/C. A primary ZAB utilizing this material achieves an open-circuit voltage of 1.51 V and a peak power density of 217 mW cm⁻². This metal-free, self-templating presents a scalable route for the generating and producing of high-performance oxygen reduction reaction catalysts for ZABs. Full article

The electrochemical properties of the hydrophobic room-temperature ionic liquid 1-propyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (PMMIm(TFSI)) were investigated, for the first time, using an electrochemical double-layer capacitor-mimicking cell containing two identical-sized micro–mesoporous molybdenum carbide-derived carbon electrodes (MMP-C(Mo₂C)), by applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Surprisingly, despite the substitution of the slightly acidic hydrogen atom with a methyl group at the carbon atom located between two nitrogen atoms in the imidazolium cation, the EIS and CV measurements demonstrated that PMMIm(TFSI) began to decompose electrochemically at the same cell potential (ΔE) as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm(BF₄)), specifically at ΔE = 2.75 V. However, the CV and EIS data indicated that PMMIm(TFSI) decomposed with a significantly lower intensity than EMIm(BF₄). Therefore, we believe that the use of PMMIm(TFSI) as the electrolyte will enable the construction of safer supercapacitors that can tolerate short periods of over-polarization up to ΔE = 4.0 V. However, when the ΔE ≤ 3.2 V was applied, EMIm(BF₄) offered higher maximum power compared to PMMIm(TFSI). We found that the calculated maximum gravimetric power precisely describes the maximum ΔE applicable for a supercapacitor candidate. Full article

Carbon is predominantly used in zinc-ion hybrid capacitors (ZIHCs) as an electrode material. Nitrogen doping and strategic design can enhance its electrochemical properties. Melamine formaldehyde resin, serving as a hard carbon precursor, synthesizes nitrogen-doped porous carbon after annealing. Incorporating transition metal catalysts like Ni, Co, and Fe alters the morphology, pore structure, graphitization degree, and nitrogen doping types/proportions. Electrochemical tests reveal a superior capacitance of 159.5 F g⁻¹ at a scan rate of 1 mV s⁻¹ and rate performance in Fe-catalyzed N-doped porous carbon (Fe-NDPC). Advanced analysis shows Fe-NDPC’s high graphitic nitrogen content and graphitization degree, boosting its electric double-layer capacitance (EDLC) and pseudocapacitance. Its abundant micro- and mesopores increase the surface area fourfold compared to non-catalyzed samples, favoring EDLC and fast electrolyte transport. This study guides catalyst application in carbon materials for supercapacitors, illuminating how catalysts influence nitrogen-doped porous carbon structure and performance. Full article

Polymers with micro- and mesoporous structure are promising as materials for gas storage and separation, encapsulating agents for controlled drug release, carriers for catalysts and sensors, precursors of nanostructured carbon materials, carriers for biomolecular immobilization and cellular scaffolds, as materials with a low dielectric constant, filtering/separating membranes, proton exchange membranes, templates for replicating structures, and as electrode materials for energy storage. Sol–gel technologies, track etching, and template synthesis are used for their production, including in micelles of surfactants and microemulsions and sublimation drying. The listed methods make it possible to obtain pores with variable shapes and sizes of 5–50 nm and achieve a narrow pore size distribution. However, all these methods are technologically multi-stage and require the use of consumables. This paper presents a review of the use of macromolecular architecture in the synthesis of micro- and mesoporous polymers with extremely high surface area and hierarchical porous polymers. The synthesis of porous polymer frameworks with individual functional capabilities, the required chemical structure, and pore surface sizes is based on the unique possibilities of developing the architecture of the polymer matrix. Full article

Atomically dispersed Fe-N-C catalysts for the oxygen reduction reaction (ORR) have been synthesized with a template-free method using carbon xerogels (CXG) as a porous matrix. The porosity of the CXGs is easily tunable through slight variations in the synthesis procedure. In this work, CXGs are prepared by formaldehyde and resorcinol polymerization, modifying the pH during the process. Materials with a broad range of porous structures are obtained: from non-porous to micro-/meso-/macroporous materials. The porous properties of CXG have a direct effect on Fe-N-CXG activity against ORR in an acidic medium (0.5 M H₂SO₄). Macropores and wide mesopores are vital to favor the mass transport of reagents to the active sites available in the micropores, while narrower mesopores can generate additional tortuosity. The role of microporosity is investigated by comparing two Fe-N-C catalysts using the same CXG as the matrix but following a different Fe and N doping procedure. In one case, the carbonization of CXG occurs rapidly and simultaneously with Fe and N doping, whereas in the other case it proceeds slowly, under controlled conditions and before the doping process, resulting in the formation of more micropores and active sites and achieving higher activity in a three-electrode cell and a better durability during fuel cell measurements. This work proves the feasibility of the template-free method using CXG as a carbon matrix for Fe-N-C catalysts, with the novelty of the controlled porous properties of the carbon material and its effect on the catalytic activity of the Fe-N-C catalyst. Moreover, the results obtained highlight the importance of the carbon matrix’s porous structure in influencing the activity of Fe-N-C catalysts against ORR. Full article

This study investigates three carbide-derived carbon (CDC) materials (TiC, NbC, and Mo₂C) characterized by uni-, bi-, and tri-modal pore sizes, respectively, for energy storage in both neat and acetonitrile-diluted 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A distribution of micro- and mesopores was studied through low-temperature N₂ and CO₂ adsorption. To elucidate the relationships between porosity and the electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were conducted using three-electrode test cells. The ultramicroporous TiC-derived carbon is characterized by a high packing density of 0.85 g cm⁻³, resulting in superior cathodic and anodic capacitances for both neat ionic liquid (IL) and a 1.9 M IL/acetonitrile electrolyte (93.6 and 75.8 F cm⁻³, respectively, in the dilute IL). However, the bi-modal pore-sized microporous NbC-derived carbon, with slightly lower cathodic and anodic capacitances (i.e., 85.0 and 73.7 F cm⁻³ in the dilute IL, respectively), has a lower pore resistance, making it more suitable for real-world applications. A symmetric two-electrode capacitor incorporating microporous CDC-NbC electrodes revealed an acceptable cycle life. After 10,000 cycles, the cell retained approximately 75% of its original capacitance, while the equivalent series resistance (ESR) only increased by 13%. Full article

N-doping is a very useful method to improve the electrochemical performance of porous carbon (PC) materials. In this study, the potential of furfural residue (FR), a solid waste in furfural production, as a precursor to producing PC materials for supercapacitors was highlighted. To obtain an N-doped PC with a high specific surface area (SSA) and hierarchical porous structure, the urea-KOH synergistic activation method was proposed. The obtained FRPCK-Urea showed a high SSA of 1850 m² g⁻¹, large pore volume of 0.9973 cm³ g⁻¹, and interconnected micro/mesoporous structure. Besides, urea can also serve as a nitrogen source, resulting in a high N content of 5.31% in FRPCK-Urea. These properties endow FRPCK-Urea with an excellent capacitance of 222.7 F g⁻¹ at 0.5 A g⁻¹ in 6 mol L⁻¹ KOH aqueous electrolyte in a three-electrode system. The prepared FRPCK-Urea possessed a well capacitance retention at current densities from 0.5 to 20 A g⁻¹ (81.90%) and cycle durability (96.43% after 5000 cycles), leading to FRPCK-Urea to be a potential electrode material for supercapacitors. Therefore, this work develops an effective way for the high-valued utilization of FR. Full article

Biorefineries with the significant amounts of lignin as a by-product have a potential to increase business revenues by using this residue to produce high value-added materials. The carbon materials from biomass waste increases the profitability of the production of porous carbon used for sorbents and energy production. The purpose of this research is to study the chemical properties of lignin from “Sweetwoods” biorefinery as well as to characterize lignin carbonizates and activated carbons synthesized from them. This paper describes the effect of carbonization conditions (thermal or hydrothermal) on the properties of activated carbon material. It can be concluded that, depending on the carbonization method, the three-dimensional hierarchical porous structure of activated carbon materials based on “Sweetwoods” lignin, has micro- and mesopores of various sizes and can be used for number of purposes: both for high-quality sorbents, catalysts for electrochemical reduction reactions, providing sufficient space for ion mass transfer in electrodes for energy storage and transfer. Full article

Nitrogen-doped activated carbons with controlled micro- and mesoporosity were obtained from wood and wastes via chemical processing using pre-treatment (pyrolysis at 500 °C and hydrothermally carbonization at 250 °C) and evaluated as oxygen reduction catalysts for further application in fuel cells. The elemental and chemical composition, structure and porosity, and types of nitrogen bonds of obtained catalyst materials were studied. The catalytic activity was evaluated in an alkaline medium using the rotating disk electrode method. It was shown that an increase in the volume of mesopores in the porous structure of a carbon catalyst promotes the diffusion of reagents and the reactions proceed more efficiently. The competitiveness of the obtained carbon materials compared to Pt/C for the reaction of catalytic oxygen reduction is shown. Full article

This study used a physical activation method to prepare asphalt-pitch-derived activated carbon (Pitch AC) for an electric double-layer capacitor (EDLC) electrode. X-ray diffraction analysis and Raman spectroscopy were used to estimate the change in the crystal structure of Pitch AC with activation time. In addition, the textural properties of Pitch AC were studied by Brunauer-Emmett-Teller (BET), Dubinin-Radushkevich (DR) and non-localized density functional theory (NLDFT) equations with N₂/77K isotherm adsorption-desorption curves. The electrochemical performance of the Pitch AC was analyzed using a coin-type EDLC with 1 M SBPBF₄/PC via galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy. The specific surface area and total pore volume were 990–2040 m²/g and 0.42–1.51 cm³/g, respectively. The pore characteristics of the Pitch AC varied according to the activation time and changed from a microporous structure to a micro-mesoporous structure as the activation time increased. The electrochemical performance analysis also found that the specific capacity was increased from 43.6 F/g to 84.5 F/g at 0.1 A/g as activation time increased. In particular, Pitch AC-9 exhibited the best electrochemical performance (rectangular CV curve, reversible GCD, lowest ion charge transfer resistance and Warburg impedance). In addition, Pitch AC-9 was confirmed to have a specific capacitance similar to commercial activated carbon for EDLC (YP-50F). Therefore, it was considered that Pitch AC could replace commercial activated carbon for EDLC because it has excellent pore characteristics and electrochemical performance despite being manufactured through a very low-cost precursor and a simple process (physical activation method). Full article

MOF-derived carbon (MDC) and metal oxide (MDMO) are superior materials for supercapacitor electrodes due to their high specific capacitances, which can be attributed to their high porosity, specific surface area (SSA), and pore volume. To improve the electrochemical performance, the environmentally friendly and industrially producible MIL-100 (Fe) was prepared using three different Fe sources through hydrothermal synthesis. MDC-A with micro- and mesopores and MDC-B with micropores were synthesized through carbonization and an HCl washing process, and MDMO (α-Fe₂O₃) was obtained by a simple sintering in air. The electrochemical properties in a three-electrode system using a 6 M KOH electrolyte were investigated. These novel MDC and MDMO were applied to an asymmetric supercapacitor (ASC) system to overcome the disadvantages of traditional supercapacitors, enhancing energy density, power density, and cyclic performance. High SSA materials (MDC-A nitrate and MDMO iron) were selected for negative and positive electrode material to fabricate ASC with KOH/PVP gel electrolyte. As-fabricated ASC resulted in high specific capacitance 127.4 Fg⁻¹ at 0.1 Ag⁻¹ and 48.0 Fg⁻¹ at 3 Ag⁻¹, respectively, and delivered superior energy density (25.5 Wh/kg) at a power density 60 W/kg. The charging/discharging cycling test was also conducted, indicating 90.1% stability after 5000 cycles. These results indicate that ASC with MDC and MDMO derived from MIL-100 (Fe) has promising potential in high-performance energy storage devices. Full article

Developing advanced carbon materials by utilizing biomass waste has attracted much attention. However, porous carbon electrodes based on the electronic-double-layer-capacitor (EDLC) charge storage mechanism generally presents unsatisfactory capacitance and energy density. Herein, an N-doped carbon material (RSM-0.33-550) was prepared by directly pyrolyzing reed straw and melamine. The micro- and meso-porous structure and the rich active nitrogen functional group offered more ion transfer and faradaic capacitance. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) measurements were used to characterize the biomass-derived carbon materials. The prepared RSM-0.33-550 possessed an N content of 6.02% and a specific surface area of 547.1 m² g⁻¹. Compared with the RSM-0-550 without melamine addition, the RSM-0.33-550 possessed a higher content of active nitrogen (pyridinic-N) in the carbon network, thus presenting an increased number of active sites for charge storage. As the anode for supercapacitors (SCs) in 6 M KOH, RSM-0.33-550 exhibited a capacitance of 202.8 F g⁻¹ at a current density of 1 A g⁻¹. At a higher current density of 20 A g⁻¹, it still retained a capacitance of 158 F g⁻¹. Notably, it delivered excellent stability with capacity retention of 96.3% at 20 A g⁻¹ after 5000 cycles. This work not only offers a new electrode material for SCs, but also gives a new insight into rationally utilizing biomass waste for energy storage. Full article

The surface properties and the hierarchical pore structure of carbon materials are important for their actual application in supercapacitors. It is important to pursue an integrated approach that is both easy and cost-effective but also challenging. Herein, coal-based hierarchical porous carbon with nitrogen doping was prepared by a simple dual template strategy using coal as the carbon precursor. The hierarchical pores were controlled by incorporating different target templates. Thanks to high conductivity, large electrochemically active surface area (483 m² g⁻¹), hierarchical porousness with appropriate micro-/mesoporous channels, and high surface nitrogen content (5.34%), the resulting porous carbon exhibits a high specific capacitance in a three-electrode system using KOH electrolytes, reaching 302 F g⁻¹ at 1 A g⁻¹ and 230 F g⁻¹ at 50 A g⁻¹ with a retention rate of 76%. At 250 W kg⁻¹, the symmetrical supercapacitor assembled at 6 M KOH shows a high energy density of 8.3 Wh kg^−1, and the stability of the cycling is smooth. The energy density of the symmetric supercapacitor assembled under ionic liquids was further increased to 48.3 Wh kg⁻¹ with a power output of 750 W kg⁻¹ when the operating voltage was increased to 3 V. This work expands the application of coal-based carbon materials in capacitive energy storage. Full article

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m² g⁻¹) and large pore volumes (0.925 to 1.346 cm³ g⁻¹) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g⁻¹ at a 1 A g⁻¹ current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g⁻¹ at 1 A g⁻¹ with sustained 50% capacitance at 10 A g⁻¹ accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications. Full article

The electrical double-layer supercapacitance performance of the nanoporous carbons prepared from the Phyllanthus emblica (Amala) seed by chemical activation using the potassium hydroxide (KOH) activator is reported. KOH activation was carried out at different temperatures (700–1000 °C) under nitrogen gas atmosphere, and in a three-electrode cell set-up the electrochemical measurements were performed in an aqueous 1 M sulfuric acid (H₂SO₄) solution. Because of the hierarchical pore structures with well-defined micro- and mesopores, Phyllanthus emblica seed-derived carbon materials exhibit high specific surface areas in the range of 1360 to 1946 m² g⁻¹, and the total pore volumes range from 0.664 to 1.328 cm³ g⁻¹. The sample with the best surface area performed admirably as the supercapacitor electrode-material, achieving a high specific capacitance of 272 F g⁻¹ at 1 A g⁻¹. Furthermore, it sustained 60% capacitance at a high current density of 50 A g⁻¹, followed by a remarkably long cycle-life of 98% after 10,000 subsequent charging/discharging cycles, demonstrating the electrode’s excellent rate-capability. These results show that the Phyllanthus emblica seed would have significant possibilities as a sustainable carbon-source for the preparing high-surface-area activated-carbons desired in high-energy-storage supercapacitors. Full article