Carbon Trends最新文献

This study used a scalable process to fabricate activated carbon (AC) supercapacitor electrodes with cornstarch as a green binder. A vital aspect of this study was comparing its performance with synthetic binders like polyvinylidene fluoride (PVDF) and Nafion. The chemical and physical properties of the AC were characterized using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and Field Emission Scanning Electron Microscopy (FE-SEM). Water contact angle measurements evaluated the hydrophilicity of AC-based electrodes with different binders. Their electrochemical characteristics were studied using open circuit potential (OCP), cyclic voltammetry (CV), galvanic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M NaSO4 electrolyte, and the charge storage mechanism was discussed in detail. The starch binder significantly facilitated the charge storage mechanism by suppressing diffusion limitations compared to other binders. The fabricated symmetric supercapacitor device of starch-based electrodes exhibited the highest C_s of 120 F/g at a specific current of 1 A g^-1 with a high energy density of 135 Wh/kg and an exact power density of 750 W/kg. The starch-based supercapacitor device exhibited a capacitance retention of 104 % and 65.5 % at specific currents of 2 A g^-1 and 10 A g^-1 after 10,000 cycles of charging/discharging, respectively.

This study explored the impact of pyrolysis heating rates ranging from 1 to 20 K min⁻¹ (final temperature 500 °C) on the porosity of resorcinol-formaldehyde based carbonaceous xerogels soft-templated with Pluronic F-127. We primarily utilized thermoporometry (differential scanning calorimetry technique) and, to a lesser extent, conventional nitrogen adsorption at −196 °C to analyze the porosity of the resulting carbons. Additionally, we examined the effects of particle size and the scale of the pyrolysis experiment, comparing a laboratory furnace with a thermal analyzer. At lower heating rates, particularly in a thermal analyzer, mesopores approximately 7–8 nm in size were observed. An increase in the heating rate resulted in larger mesopores, from 7 to 17 nm, widened pore size distribution (PSD), and a rise in mesopore volume from 0.21 to 0.53 cm³ g⁻¹. Higher heating rates (> 5 K min^-1) also accelerated the decomposition of the Pluronic F-127, leading to fast gas release, which subsequently caused cracking of the carbon skeleton and widening of the pores. Pyrolysis heating rate had no significant effect on the degree of graphitization in the pyrolyzed samples. Particle size showed minimal influence on porosity when xerogels were pyrolyzed at either the minimal or maximal heating rates in the thermal analyzer. However, experiments conducted in a laboratory furnace at the lowest heating rate demonstrated that imprecise temperature control and fluctuations can lead to the formation of larger mesopores.

Nowadays we are extremely dependent on various synthetic plastic materials to maintain the massive demand, therefore, both the industries and mankind have been generating a massive amount of plastic waste which is so hazardous for the total environment due to their nonbiodegradable nature. To solve this problem by replacing the fossil-based plastic materials with ecofriendly biopolymers in this current study we will be described a novel method for producing Crystalline Nano Cellulose (CNC) from the waste sugarcane leaf sheaths (SLSF) fibers as a green reinforcing agent. The waste-to-wealth approach aims to elevate agricultural residues, particularly SLSF, by transforming them into high-quality CNCs for use in a variety of sectors. SLSF was initially washed with detergent to remove impurities, followed by alkali treatment and bleaching operation before CNC manufacture using acid hydrolysis (60% H₂SO₄). The resulting materials were characterized using Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Differential thermogravimetry (DTG), and Differential thermal analysis (DTA). FTIR indicates the newly produced CNCs is very much rich with active sites like –OH, -NH, -COOH, -C-O-C-, etc., while SEM revealed the raw fiber surface was rough, whereas the surface of CNCs became smooth even after the removal of lignin, fatty, and waxy compounds. Overall, acid hydrolysis was shown to increase the crystallinity of bleached SLSF while reducing cellulose dimensions to the nanoscale. After analysis it was revealed that most CNC particle size was around 100 nm. The outstanding properties of CNCs, including as high strength, biodegradability, and low environmental impact, make them ideal candidates for reinforcing composites, improving medicine delivery systems, and aiding new electronics. Ongoing research and technology advancements in integrating CNCs into many applications have the potential to alter industries looking for sustainable and high-performance materials.

Activated carbons (ACs) derived from waste rice husk ash (RHA) exhibit remarkable potential for selective oxygen adsorption. The pore morphology of the prepared materials was characterized utilizing BET measurement, t-plot, and BJH-plot suggesting a linear relation between activation temperature and mesopore volume, whereas, micropore volume decreases at activation beyond 550 °C. FT-IR spectroscopy confirms their non-polar surface. Notably, AC-600 achieves an outstanding O₂/N₂ (0.21/0.78) of 152.7 at 0.01 bar at 25 °C, owing to the non-polar nature of the surface, favouring oxygen adsorption due to its low quadrupole moment. Additionally, the mixed micro and mesoporous structure of AC-600 significantly enhance the oxygen adsorption, showing an ∼18.4% (or 1.2-fold) increase compared to AC-500. However, a ∼32.3% decrease in oxygen uptake was observed for AC-800 due to excessive “burn-off”. Adsorption selectivity, assessed with Ideal Adsorption Solution Theory (IAST) and fitted to the Freundlich isotherm model, and adsorption kinetics, analysed using the pseudo-second-order Lagergren and Webber-Morris intraparticle diffusion models, highlighted the impact of activation temperature on the porosity of the material. Understanding the surface chemistry and pore morphology of activated carbon offers deeper insights to enhance oxygen uptake capacity, advancing the development of sustainable, industrially viable materials for oxygen production.

Free-standing electrode materials provide many desirable properties for electrochemical energy storage devices due to their light weight, good conductive capacity, excellent mechanical strength, high energy/power density and extraordinary electrochemical stability. Particularly, carbonaceous matrix nanomaterials, such as graphene materials, carbon nanotubes, carbon nanofibers, carbon papers and carbon cloths, play important roles in the free-standing electrodes, including serving as conducting network skeleton, loading electrochemically active material, enhancing mechanical toughness and flexibility, and preventing the structural damage during charge/discharge processes. In this review, we give a systematic overview of the state-of-the-art research progress on carbonaceous matrixes-based free-standing electrode materials for electrochemical energy storage, from synthesis methods, structural design, to important applications in flexible energy storage devices including lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, lithium-oxygen batteries, and supercapacitors for each class of matrix-based electrode materials. In particular, the structure design strategies utilizing the advantages of free-standing matrixes to address the existing issues and improve the electrochemical and mechanical performance of energy storage devices are discussed in detail. At the end, we also discuss the challenges and demonstrate the prospective for the future development of such materials for advanced flexible energy storage devices.

A rectangular graphyne sheet is composed of units similar to phenyl rings that are linked by acetylenic chains, as in hexagonal $\gamma$-graphyne. This system is organized over a rectangular lattice similar to that of the recently synthesized biphenylene network. We investigate the stability of this layered material from different perspectives and study its electronic structure. Rectangular graphyne is a semiconducting system in its pristine form. It features a pair of highly localized states. These characteristics are correlated with the structural anisotropy of the system, since its frontier states behave like quasi-1D states embedded in the 2D lattice. We further consider modified systems in which longer acetylenic links are introduced. We discuss how a strategic choice of the position of these longer bridges leads to specific changes of the electronic structure of the rectangular graphyne sheet.

Poly(heptazine imide) (PHI), a carbon nitride polymer, is a highly efficient visible-light-driven photocatalytic material. We aimed to improve its photocatalytic performance for CO₂ conversion. We prepared M-PHIs by encapsulating different metals (M = K, Li, Rb, and Na) and H-PHIs, in which the metal of each M-PHI was ion-exchanged with a proton. We evaluated their photocatalytic activities for CO₂ conversion and found that Na-PHI and H-PHI, prepared from Na-PHI (H-PHI(NaCl)), showed more than twice the CO production efficiency of melon and other PHIs.

The high CO production efficiency of Na-PHI and H-PHI(NaCl) was attributed to their extremely smaller particle size compared with those of the other PHIs. By closely examining the synthesis conditions of Na-PHI, we have identified a method to intentionally synthesize M-PHI with small particle size. These results provide a new strategy for highly efficient CO₂ conversion using PHI.