Hierarchical Porous Carbon Microfibers Derived from Tamarind Seed Coat for High-Energy Supercapacitor Application

Sustainable synthesis of spongy-like porous carbon for supercapacitive energy storage systems towards pollution control

In this study, the fruit of Terminalia chebula, commonly known as chebulic myrobalan, is used as the precursor for carbon for its application in supercapacitors. The Terminalia chebula biomass-derived sponge-like porous carbon (TC-SPC) is synthesized using a facile and economical method of pyrolysis. TC-SPC thus obtained is subjected to XRD, FESEM, TEM, HRTEM, XPS, Raman spectroscopy, ATR-FTIR, and nitrogen adsorption-desorption analyses for their structural and chemical composition. The examination revealed that TC-SPC has a crystalline nature and a mesoporous and microporous structure accompanied by a disordered carbon framework that is doped with heteroatoms such as nitrogen and sulfur. Electrochemical studies are performed on TC-SPC using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. TC-SPC contributed a maximum specific capacitance of 145 F g-1 obtained at 1 A g-1. The cyclic stability of TC-SPC is significant with 10,000 cycles, maintaining the capacitance retention value of 96%. The results demonstrated that by turning the fruit of Terminalia chebula into an opulent product, a supercapacitor, TC-SPC generated from biomass has proven to be a potential candidate for energy storage application.

Valorization of orange peel waste to tunable heteroatom-doped hydrochar-derived microporous carbons for selective CO2 adsorption and separation

Constrained by the extortionately expensive carbon sources, low carbon yields, inadequate adsorption capacities, and corrosive chemical activating agents, the commercialization of carbonaceous CO₂ adsorbents remains a challenging task. Herein, potassium oxalate (K₂C₂O₄), an activating agent with less corrosive properties, was used for the synthesis of activated carbons from inexhaustibly available "orange peel biowaste." For the first time, a comprehensive report is presented on the effect of hydrothermal treatment, hydrochar/K₂C₂O₄ ratio, activation temperature, and melamine modification in tailoring the porosity and surface functionalization of activated carbons. The optimized sample, OPMK-900, exhibited large specific surface area ~2130 m²/g; micropore volume ~1.1166 cm³/g, and a high pyrrolic nitrogen content (~ 46.1 %). Notably, melamine played the dual role as a promoter to K₂C₂O₄ porosity generation and a nitrogen dopant, which synergistically led to an efficient CO₂ uptake of ~6.67 mmol/g at 273 K/ 1 bar via micropore-filling mechanism and Lewis acid-base interactions. Moreover, remarkably high IAST CO₂/N₂ selectivity (105 at 273 K and 96 at 298 K) surpasses most of the biomass-derived carbons. Furthermore, the moderately high isosteric heat of adsorption (∆H_ads ~ 38.9 kJ/mol) revealed the physisorption mechanism of adsorption with a limited energy requirement for the regeneration of the spent adsorbents.

Tamarindus indica seed-shell nanoparticles‑silver nanoparticles-Ceratonia silique bean gum composite for copper-micro mesh grid electrode fabrication and its application for glucose detection in artificial salivary samples

This study used a new approach to fabricate a glucose detection system based on nano-engineered biomaterials. The fabrication steps included strategic synthesis, integration and stabilization of biological and metal nanoparticles in superabsorbent hydrogel gum matrix. The design of the high-performance electrochemical biosensor platform includes copper-micro mesh grid electrode modified with polymer phase comprising of silver nanoparticles surface coroneted with Ceratonia silique locust bean gum (LBG), Tamarindus indica seed-shell nanoparticles and glucose oxidase (GOx). Fundamental assessment of catalytic properties of the nanobiocomposite films on copper grid probe were performed by cyclic voltammetry, amperometry, differential pulse voltammetry. Probes showed good repeatability, reproducibility, selectivity, and long-term stability. The GOx was well-immobilized and stabilized by C. siliqua nano-matrix, with 85% and 98% activity retention when stored at different condiions for 6 month and 3 months, respectively. The fabricated grid-platform exhibited linear response in a wide range of glucose concentration, with detection limit of 1.0 nM (S/N = 3) and sensitivity 38.7 mA nM^-1 cm^-2. The bionanomaterial-based sensor was successfully applied for ultra-low glucose detection in artificial salivary samples. The designed sensor, perhaps with further modifications, has potential for the next generation of sensing platform in various biological fluids especially for non-invasive glucose detection for diabetic patients.

Promising High-Performance Supercapacitor Electrode Materials from MnO2 Nanosheets@Bamboo Leaf Carbon

MnO₂@bamboo leaf (BL) carbon composites have been prepared by a hydrothermal method, wherein, the BL porous carbon structure was based on BLs. The MnO₂@BL composites were characterized by SEM, TEM, XRD, Raman, XPS, and TGA. The electrochemical properties of the composites were investigated in a three-electrode system using 1 M Na₂SO₄ aqueous solution as an asymmetric supercapacitor electrolyte. Electrochemical measurements showed that the MnO₂@BL composites can be applied in asymmetric supercapacitors and exhibited a good cycling stability with a capacitance retention ratio of 85.3% after 5000 cycles (at 0.5 A g^-1). The MnO₂@BL composites were promising materials for application in supercapacitors.

Efficient Toluene Adsorption on Metal Salt-Activated Porous Carbons Derived from Low-Cost Biomass: A Discussion of Mechanism

Porous carbons (PCS) derived from sodium lignin sulfonate were activated by four common metal salts. The samples exhibit distinct characteristics of irregular, sunflower-like, interconnected sheet, and tine block morphologies under the impact of NaCl, CaCl₂, ZnCl₂, and FeCl₃, respectively (PCS-MCl _x ). Surprisingly, the maximum and minimum specific surface areas are 1524 and 44 m²/g corresponding to PCS-ZnCl₂ and PCS-NaCl. All of the samples have plentiful functional groups; herein, PCS-NaCl and PCS-FeCl₃ are detected with the highest O and S contents (11.85, 1.08%), respectively, which signifies sufficient active sites for adsorption. These porous materials were applied in toluene adsorption from paraffin liquid and matched the Langmuir isotherm models well. Thus, the activation mechanism was discussed in detail. PCS-MCl _x has a completely different pyrolysis behavior according to thermogravimetry/derivative thermogravimetry (TG/DTG) analysis. It is speculated that H[ZnCl₂(OH)] would have an etching effect on the carbon structure of PCS-ZnCl₂, and HCl or H₂SO₄, resulting from FeCl₃ hydrolysis and a reduction reaction, would be corrosive to the sodium lignin sulfonate (SLS) surface. Each metal salt plays a different role in activation. The devised method for the synthesis of porous carbons is green and economical, which is suited to mass production.

Properties of -O-Cu-O- Bridged Copper Phosphate-Based Thermal Insulation Materials

P-O-H polycondensation -O-Cu-O- ion-bonded bridges were formed in copper phosphate thermal insulation materials by mixing Al(OH)₃ dissolved in H₃PO₄ with CuO filler and Al₂O₃, SiC, ZrC, and Cr₂O₃ as curing accelerators, alone or in combination. The effects of different additive combinations on the curing behavior and thermal stability of the copper phosphate thermal insulation material matrixes were compared using thermogravimetry/differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. The copper phosphate materials exhibit good thermal stabilities and low thermal conductivities. The thermal weight losses before and after ceramic reinforcement were 4-19.8 and 3.8-9.4%, respectively, and the thermal conductivities of the P-O-H polycondensation -O-Cu-O- ion-bonded bridges formed in the copper phosphate thermal insulation materials were in the range of 0.656-1.824 W/(m·K).

High Specific Capacitance Electrode Material for Supercapacitors Based on Resin-Derived Nitrogen-Doped Porous Carbons

Carbon-based materials, as electrodes for supercapacitors, have attracted tremendous attention. Therefore, nitrogen-doped porous carbons (NPCs) were prepared through a facile carbonization/activation strategy by treating different mass ratios of melamine-urea-formaldehyde resin and KOH. It is clearly demonstrated that because of the introduction of KOH, the resulting NPCs were shown to have increased specific surface area and a rich pore structure, and the best sample possessed a large specific surface area of 2248 m² g^-1 and high N content, which contributed to the good electrochemical performance for supercapacitors. Accordingly, a three-electrode system assembles NPCs as an electrode using aqueous KOH solution; the specific capacitance was 341 F g^-1 under the current density of 1 A g^-1 and retained a specific capacitance of almost 92% after 5000 cycles. The maximum energy output for a symmetrical solid-state supercapacitor with NPCs as the electrode material was 9.60 W h kg^-1 at 1 A g^-1. NPCs have promising applications on high-performance supercapacitors and other energy-storage devices.

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption

Currently, electromagnetic (EM) pollution poses severe complication toward the operation of electronic devices and biological systems. To this end, it is pertinent to develop novel microwave absorbers through compositional and structural design. Porous carbon (PC) materials demonstrate great potential in EM wave absorption due to their ultralow density, large surface area, and excellent dielectric loss ability. However, the large-scale production of PC materials through low-cost and simple synthetic route is a challenge. Deriving PC materials through biomass sources is a sustainable, ubiquitous, and low-cost method, which comes with many desired features, such as hierarchical texture, periodic pattern, and some unique nanoarchitecture. Using the bio-inspired microstructure to manufacture PC materials in mild condition is desirable. In this review, we summarize the EM wave absorption application of biomass-derived PC materials from optimizing structure and designing composition. The corresponding synthetic mechanisms and development prospects are discussed as well. The perspective in this field is given at the end of the article.