Hierarchical porous carbon microtubes derived from corn silks for supercapacitors electrode materials

Turning mango kernel waste into high-energy porous carbon: a sustainable electrode material for high-performance supercapacitors with exceptional stability

This study explores the sustainable production of high-performance supercapacitor electrodes from waste mango kernels, addressing the growing need for eco-friendly energy storage solutions. Porous carbon materials were synthesized via pyrolysis at varying temperatures (700, 800, 900, and 1000 °C), designated as MK7, MK8, MK9, and MK10, respectively. The synthesized carbon was obtained via a simple and eco-friendly carbonization, yielding a highly porous structure with a large specific surface area of 1348.9 m2 g-1, for MK9 material as confirmed by BET analysis. Raman spectroscopy revealed a high degree of graphitization with D and G bands, indicating the presence of both disordered and graphitic carbon domains. SEM imaging showed a well-developed, interconnected porous morphology, while XRD patterns confirmed the amorphous nature with partially crystalline domains. The resulting carbon materials were evaluated for their electrochemical performance in supercapacitor applications. Electrochemical characterization revealed that the MK9 sample, pyrolyzed at 900 °C, exhibited the highest specific capacitance of 205.8 F g-1, surpassing the performance of the other samples. To optimize device performance, symmetric supercapacitors were fabricated using a CR2032 coin cell configuration with different electrolytes and concentrations. The KOH electrolyte device demonstrated a maximum power density of 5137.86 W kg-1, an energy density of 12.32 W h kg-1, and a specific capacitance of 112.4 F g-1. Furthermore, this device exhibited excellent cycling stability, maintaining its performance over 100 000 galvanostatic charge-discharge cycles. A practical demonstration showed the ability of the device to power a red LED for approximately 15 minutes. These results highlight the potential of utilizing waste biomass, specifically mango kernels, for sustainable and efficient supercapacitor development.

Optimized mesopore design in ginkgo nuts-derived hyper-crosslinked porous carbon for enhancing supercapacitor capacitance performance

The capacitance performance of a co-doped carbon-based supercapacitor derived from Ginkgo nuts was significantly enhanced by optimizing the mesoporous structure through high-temperature pyrolysis combined with KOH activation. The precisely engineered GBHHPC-750-4 is characterized by a hyper-crosslinked 3D hierarchical porous structure, with an exceptionally high specific surface area of 3163.9 m2/g, a substantial mesopore proportion (Vmeso/Vt = 74.1 %), a broad pore size range of 2-10 nm, and elevated levels of heteroatom doping (3.4 at.% N, 8.3 at.% O, 1.6 at.% P). The symmetric supercapacitor based on the GBHHPC-750-4 electrode exhibits a peak specific capacitance of 256 F/g at 1 A/g, achieves an energy density of 118.2 Wh kg-1, maintains an impressive rate capability of 63.6 % across a wide current range (0.5-20 A/g) and demonstrates a prolonged cycle lifespan with 88.0 % capacitance retention after 5000 cycles in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMBF4) electrolyte, emphasizing the substantial potential of the optimized mesoporous carbon material for energy storage applications.

PEDOT-Doped Mesoporous Nanocarbon Electrodes for High Capacitive Aqueous Symmetric Supercapacitors

Poly(3,4-ethylenedioxythiophene) (PEDOT) and PEDOT-functionalized carbon nanoparticles (f-CNPs) were synthesized by in situ chemical oxidative polymerization and pyrolysis methods. f-CNP-PEDOT nanocomposites were prepared by varying the concentration of PEDOT from 1 to 20% by weight (i.e., 1, 2.5, 5, 10, and 20 wt%). Several characterization techniques, such as field-emission scanning electron microscopy (FESEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray diffraction (XRD), N2 Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses, as well as cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS), were applied to investigate the morphology, the crystalline structure, the N2 adsorption/desorption capability, as well as the electrochemical properties of these new synthesized nanocomposite materials. FESEM analysis showed that these nanocomposites have defined porous structures, and BET surface area analysis showed that the standalone f-CNP exhibited the largest surface area of 801.6 m2/g, whereas the f-CNP-PEDOT with 20 wt% exhibited the smallest surface area of 116 m2/g. The BJH method showed that the nanocomposites were predominantly mesoporous. CV, GCD, and EIS measurements showed that f-CNP functionalized with 5 wt% PEDOT had a higher capacitive performance compared to the individual f-CNPs and PEDOT constituents, exhibiting an extraordinary specific capacitance of 258.7 F/g, at a current density of 0.25 A/g, due to the combined advantage of enhanced electrochemical activity induced by PEDOT doping, and highly developed porosity of f-CNPs. Symmetric aqueous supercapacitor devices were fabricated using the optimized f-CNP-PEDOT doped with 5 wt% of PEDOT as active material, exhibiting a high capacitance of 96.7 F/g at 1.4 V, holding practically their full charge, after 10,000 charge-discharge cycles at 2 A/g, thus providing the highest electrical electrodes performance. Hereafter, this work paves the way for the potential use of f-CNP-PEDOT nanocomposites in the development of high-energy-density supercapacitors.

Hierarchical hollow-tubular porous carbon microtubes prepared via a mild method for supercapacitor electrode materials with high volumetric capacitance

In this paper, hollow-tubular porous carbons were synthesized from abundant biomass Cycas fluff (CF) through simple carbonization followed by an NaHCO₃ mild activation process. After activation, the tubular structure of the CF was retained, and a hierarchical structure of micropores, mesopores and macropores was formed. When the optimal mass ratio of NaHCO₃/CF is 2, the obtained porous carbon CF-HPC-2 sample has a large specific surface area (SSA) of 516.70 m² g⁻¹ in Brunauer–Emmett–Teller (BET) tests and a total pore volume of 0.33 cm³ g⁻¹. The C, O, N and S contents of CF-HPC-2 were tested as 91.77 at%, 4.09 at%, 3.54 at%, and 0.6 at%, respectively, by elemental analysis. Remarkably, CF-HPC-2 exhibits a high volume capacitance (349.1 F cm⁻³ at 1 A g⁻¹) as well as a higher rate capability than other biomass carbon materials (289.1 F cm⁻³ at 10 A g⁻¹). Additionally, the energy density of the CF-HPC-2 based symmetric supercapacitor in 2 M Na₂SO₄ electrolyte at 20 kW kg⁻¹ is 27.72 W h kg⁻¹. The particular hollow tubular morphology and activated porous structure determine the excellent electrochemical performance of the material. Hence, this synthetic method provides a new way of storing energy for porous carbon as high volumetric capacitance supercapacitor materials.

In this paper, hollow-tubular porous carbons were synthesized from abundant biomass Cycas fluff (CF) through simple carbonization followed by an NaHCO₃ mild activation process.

Hydroxyl/amino and Fe(III) co-grafted graphite carbon nitride for photocatalytic removal of volatile organic compounds

Hydroxyl/amino and Fe(III) co-grafted graphite carbon nitride (CN) is fabricated via alkaline hydrothermal treatment and followed by an impregnation adsorption process. In this unique fabrication, hydroxyl and amino groups enriched on the surface play a vital role in improving the adsorption capacity for volatile organic compounds (VOCs), while the grafted amorphous Fe(III) clusters could dominantly regulate the path of molecular oxygen activation via photo-Fenton reaction, and change the selectivity of intermediate reactive oxygen species (ROS) with the assistant of the rich surficial hydroxyl groups. Meanwhile, both the grafted functional groups and Fe(III) clusters can serve as photogenerated charge acceptors for collaboratively accelerating carriers' separation. Besides, the Fe(III)-mediated interfacial charge transfer effect (IFCT) also could extend visible light absorption and boost carriers' generation. Benefiting from the virtues of the complementary and synergy of the grafted hydroxyl/amino and Fe(III), the dual-functionalized CN is qualified as an efficient photocatalyst for removal of VOCs, which exhibits 22 and 18 times isopropanol (IPA) adsorption capacity and CO₂ production than of pristine CN during photocatalytic IPA removal, respectively. Moreover, this work provides a new strategy of surficial group-cluster bifunctionalization for systematically improving sustainable solar-to-chemical energy conversion towards VOCs mineralization.