Facile fabrication of well-defined microtubular carbonized kapok fiber/NiO composites as electrode material for supercapacitor

Sorghum grain as a bio-template: emerging, cost-effective, and metal-free synthesis of C-doped g-C3N4 for photo-degradation of antibiotic, bisphenol A (BPA), and phenol under solar light irradiation

Due to the industry's rapid growth, the presence of organic pollutants, especially antibiotics, in water and wastewater resources is the main concern for wildlife and human health. Therefore, these days, a significant challenge is developing an efficient, sustainable, and eco-friendly photocatalyst. Natural biological models have numerous advantages compared to artificial model materials. Biological models with unique multi-level structures and morphology can be used to create porous bio-templates to produce hierarchical materials. So, in this work, for the first time, this was achieved by using sorghum grain seeds as a bio-template (natural waste material) and urea as a precursor, through a simple and environmentally friendly method. We believed that natural waste materials with high carbon atom content could be used as both a carbon doping agent and a bio-template, thus improving the physical and optical properties of the resulting materials. In comparison to previous studies on the synthesis of C-doped g-C3N4, our work offers a greener and more cost-effective approach to synthesis, while also reducing waste material. We succeeded in the photo-degradation of a series of organic pollutants such as phenol, bisphenol A (BPA), and amoxicillin (AMX) in an aqueous solution under solar light illumination.

P-N heterojunction NiO/ZnO nanowire based electrode for asymmetric supercapacitor applications

Nickel-based oxides are selected for their inexpensive cost, well-defined redox activity, and flexibility in adjusting nanostructures via optimization of the synthesis process. This communique explores the field of energy storage for hydrothermally synthesized NiO/ZnO nanowires by analysing their capacitive behaviour. The p-type NiO was successfully built onto the well-ordered mesoporous n-type ZnO matrix, resulting in the formation of p-n heterojunction artefacts with porous nanowire architectures. NiO/ZnO nanowire-based electrodes exhibited much higher electrochemical characteristics than bare NiO nanowires. The heterojunction at the interface between the NiO and ZnO nanoparticles, their specific surface area, as well as their combined synergetic influence, are accountable for the high specific capacitance (Cs) of 1135 Fg-1at a scan rate of 5 mV s-1. NiO/ZnO nanowires show an 18% dip in initial capacitance even after 6000 cycles, indicating excellent capacitance retention and low resistance validated by electrochemical impedance spectroscopy. In addition, the specific capacitance, energy and power density of the solid state asymmetric capacitor that was manufactured by employing NiO/ZnO as the positive electrode and activated carbon as the negative electrode were found to be 87 Fg-1, 23 Whkg-1and 614 Wkg-1, respectively. The novel electrode based on NiO/ZnO demonstrates excellent electrochemical characteristics all of which point to its promising application in supercapacitor devices.

Oil Adsorption Kinetics of Calcium Stearate-Coated Kapok Fibers

This study used a simple and efficient dipping method to prepare oleophilic calcium stearate-coated kapok fibers (CaSt₂-KF) with improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the deposition of calcium stearate particles on the surface of the kapok fibers. This led to higher surface roughness and improved static water contact angle of 137.4°. The calcium stearate-coated kapok fibers exhibited comparable sorption capacities for kerosene, diesel, and palm oil. However, the highest sorption capacity of 59.69 g/g was observed for motor oil at static conditions. For motor oil in water, the coated fibers exhibited fast initial sorption and a 65% removal efficiency after 30 s. At equilibrium, CaSt₂-KF attained a sorption capacity of 33.9 g/g and 92.5% removal efficiency for motor oil in water. The sorption kinetics of pure motor oil and motor oil in water follows the pseudo-second-order kinetic model, and the Elovich model further described chemisorption. Intraparticle diffusion and liquid film diffusion were both present, with the latter being the predominant diffusion mechanism during motor oil sorption.

Biobased Kapok Fiber Nano-Structure for Energy and Environment Application: A Critical Review

The increasing degradation of fossil fuels has motivated the globe to turn to green energy solutions such as biofuel in order to minimize the entire reliance on fossil fuels. Green renewable resources have grown in popularity in recent years as a result of the advancement of environmental technology solutions. Kapok fiber is a sort of cellulosic fiber derived from kapok tree seeds (Ceiba pentandra). Kapok Fiber, as a bio-template, offers the best alternatives to provide clean and renewable energy sources. The unique structure, good conductivity, and excellent physical properties exhibited by kapok fiber nominate it as a highly favored cocatalyst for deriving solar energy processes. This review will explore the role and recent developments of KF in energy production, including hydrogen and CO₂ reduction. Moreover, this work summarized the potential of kapok fiber in environmental applications, including adsorption and degradation. The future contribution and concerns are highlighted in order to provide perspective on the future advancement of kapok fiber.

Tannin-Mn coordination polymer coated carbon quantum dots nanocomposite for fluorescence and magnetic resonance bimodal imaging

The MR/FI bimodal imaging has attracted widely studied due to combining the advantages of MRI and FI can bridge gaps in sensitivity and depth between these two modalities. Herein, a novel MR/FI bimodal imaging probe is facile fabricated by coating the Mn-phenolic coordination polymer on the surface of the carbon quantum dots. The structure of the as-prepared nanocomposite probe is carefully validated via SEM, TEM, and XPS. The content of Mn²⁺ is calculated through the EDS and TGA. The quantum yield (QY) and emission wavelength of the probe are about 7.24% and 490 nm, respectively. The longitudinal r1 value (2.43 mM^-1 s^-1) with low r2/r1 (4.45) of the probe is obtained. Subsequently, fluorescence and MR imaging are performed. The metabolic pathways in vivo are inferred by studying the bio-distribution of the probe in major organs. Thus, these results indicate that probe would be an excellent dual-modal imaging probe for enhanced MR imaging and fluorescence imaging. MR/FI bimodal imaging probe is built via in-situ coated Mn-phenolic coordination polymer on the surface of the carbon quantum dots. The in vitro and vivo image property of the probe is evaluated.

3D hierarchical porous nitrogen-doped carbon/Ni@NiO nanocomposites self-templated by cross-linked polyacrylamide gel for high performance supercapacitor electrode

Three-dimensional nitrogen-doped carbon network incorporated with nickel@nickel oxide core-shell nanoparticles composite (3D NC/Ni@NiO) has been facilely prepared, self-templated by the cross-linked polyacrylamide aerogel precursor containing NiCl₂. Characterizations reveal that the Ni@NiO nanoparticles distribute homogeneously in the 3D nitrogen-doped carbon matrix and the composite is of hierarchical porous structure. When used as supercapacitor electrode in a three-electrode system, the 3D NC/Ni@NiO exhibits enhanced electrical conductivity and excellent electrochemical performance, presenting a high specific capacitance (389F g^-1 at 5 mV s^-1), good rate capability (276 F g^-1 at 100 mV s^-1) and outstanding cycling performance (with the capacitance retention of 70.2% after 5000 charge-discharge cycles). This is due to the synergistic effects of conductive metallic nickel, pseudocapacitive nickel oxide as well as in situ nitrogen doping of carbon network. Moreover, an asymmetric supercapacitor (ASC) was fabricated with NC/Ni@NiO as positive electrode and active carbon as negative electrode. The ASC device exhibits a maximum energy density of 19.4 W h kg^-1 at a power density of 700 W kg^-1 and shows good cycling stability (73.8% capacity retention after 3000 cycles), indicating that it has great promise for practical energy storage and conversion application.

Performance of Solid-state Hybrid Energy-storage Device using Reduced Graphene-oxide Anchored Sol-gel Derived Ni/NiO Nanocomposite

The influence of (nickel nitrate/citric acid) mole ratio on the formation of sol-gel end products was examined. The formed Ni/NiO nanoparticle was anchored on to reduced graphene-oxide (rGO) by means of probe sonication. It was found that the sample obtained from the (1:1) nickel ion: citric acid (Ni²⁺: CA) mole ratio resulted in a high specific capacity of 158 C/g among all (Ni²⁺: CA) ratios examined. By anchoring Ni/NiO on to the rGO resulted in enhanced specific capacity of as high as 335 C/g along with improved cycling stability, high rate capability and Coulombic efficiency. The high conductivity and increased surface area seemed responsible for enhanced electrochemical performances of the Ni/NiO@rGO nanocomposite. A solid-state hybrid energy-storage device consisting of the Ni/NiO@rGO (NR₂) as a positive electrode and the rGO as negative electrode exhibited enhanced energy and power densities. Lighting of LED was demonstrated by using three proto-type (NR₂⁽⁺⁾|| rGO⁽⁻⁾) hybrid devices connected in series.

Highly effective synthesis of NiO/CNT nanohybrids by atomic layer deposition for high-rate and long-life supercapacitors

Uniform and high-efficiency NiO films coated on CNTs with controllable thickness were synthesized by an ALD method, exhibiting an excellent performance for supercapacitor applications.

Facile fabrication of well-defined polyaniline microtubes derived from natural kapok fibers for supercapacitors with long-term cycling stability

Well-defined polyaniline microtubes derived from natural kapok fibers exhibit long-term cycling stability as electrode materials of supercapacitors.