Salt Template-Derived Fe-N Co-Doped Ultrathin Carbon for Boosted Performance of Supercapacitors

Heteroatoms-doped ultrathin carbon materials hold great promise for electrochemical energy application. Herein, we develop a salt-templating method to prepare three-dimensional Fe-N co-doped carbon (FeNPC) with ultrathin (~ 5-nm-thick) structural feature. The synthetic procedure involves the following steps: First, fabrication of nanoNaCl templates with uniform particle sizes (~500 nm) via one-pot solution synthesis. Second, fabrication of the precursor by encapsulating of NaCl nanoparticles via the in-situ polymerization of pyrrole monomers under vapor atmosphere. Last, FeNPC formation by subsequent pyrolysis and pickling. The optimized sample displays excellent performance as supercapacitors exhibiting 393.5 F g-1 at 1A g-1 in 6 M KOH. Furthermore, the symmetric supercapacitors assembled with the optimized sample show an energy density of 10.45 Wh kg-1 at a power density of 300 W kg-1 and outstanding cycling stability retaining 93% capacitance at 5A g-1 after 10000 cycles.

Post-Synthetic and In Situ Vacancy Repairing of Iron Hexacyanoferrate Toward Highly Stable Cathodes for Sodium-Ion Batteries

Iron hexacyanoferrate (FeHCF) is a promising cathode material for sodium-ion batteries. However, FeHCF always suffers from a poor cycling stability, which is closely related to the abundant vacancy defects in its framework. Herein, post-synthetic and in-situ vacancy repairing strategies are proposed for the synthesis of high-quality FeHCF in a highly concentrated Na4Fe(CN)6 solution. Both the post-synthetic and in-situ vacancy repaired FeHCF products (FeHCF-P and FeHCF-I) show the significant decrease in the number of vacancy defects and the reinforced structure, which can suppress the side reactions and activate the capacity from low-spin Fe in FeHCF. In particular, FeHCF-P delivers a reversible discharge capacity of 131 mAh g−1 at 1 C and remains 109 mAh g−1 after 500 cycles, with a capacity retention of 83%. FeHCF-I can deliver a high discharge capacity of 158.5 mAh g−1 at 1 C. Even at 10 C, the FeHCF-I electrode still maintains a discharge specific capacity of 103 mAh g−1 and retains 75% after 800 cycles. This work provides a new vacancy repairing strategy for the solution synthesis of high-quality FeHCF.

UV-Light Mediated Biosynthesis of Silver Nanowires; Characterization, Dye Degradation Potential and Kinetic Studies

Herrin, a simple and eco-friendly method for the synthesis of silver nanowires (Ag-NWs) has been reported. Silver nanowires were synthesized using Psidium guajava seed extract that acted as a reducing agent as well as a stabilizing agent for silver nitrate solution. Synthesis was carried out at 50 °C temperature under continuous UV-irradiation. Silver nanowires were initially characterized by a UV-visible and FTIR spectrophotometer. In addition, morphology and particle size of synthesized Ag-NWs were determined using Field Emission Scanning Electron Microscopy and X-ray diffraction (XRD) techniques. Nanowires were found to have 12.8 μm length and 200–500 nm diameter and cubic phase morphology. Furthermore, the catalytic potential of Ag-NWs for the degradation of methyl orange dye (MO) was determined. The selected dye was degraded successfully that confirmed the catalytic potential of Ag-NWs. The authors concluded that Ag-NWs can be synthesized using plant extract having excellent morphological features as well as impressive catalytic potential.

Plasma-solution synthesis of particles containing transition metals

The paper proposes a new method for the synthesis of powders containing transition metals using a plasma-solution system. The reactor was an H-shaped glass cell, the two parts of which were separated by a cellophane membrane. A discharge consisting of two discharges - with a liquid cathode and a liquid anode - a high voltage is applied to titanium electrodes located above the surface of the solution. Aqueous solutions of zinc, iron, cadmium, cobalt, nickel, and copper nitrates were used as the liquid phase. Under the action of the discharge on the liquid anode, in the region of contact of the discharge with the solution the formation of a colloidal suspension was observed. The kinetics of the process of synthesis of solid-phase particles in solution under the action of a discharge have been studied. The chemical composition and morphology of the formed solid phase have been established. The mechanisms of chemical reactions occurring in the solution under the action of plasma, and the mechanisms of formation of transition metal oxides in the process of calcining the synthesized powders have been proposed.

Piezoelectric properties of PZT by an ethylene glycol-based chemical solution synthesis

We have investigated a water-stable sol–gel method based on ethylene glycol as a solvent and bridging ligand for the synthesis of ferroelectric lead zirconate titanate in bulk and thin film forms. This method offers lower toxicity of the solvent, higher stability toward atmospheric moisture and a simplified synthetic procedure compared to traditional sol–gel methods. However, the piezoelectric properties of products produced using this method have yet to be systematically studied. We have measured the ferroelectric and piezoelectric properties and compared them to existing literature using different synthesis techniques. Ceramic pellets of Nb-doped lead zirconate titanate (PNZT) in the tetragonal phase were produced with high density and good piezoelectric properties, comparable to those reported in the literature and those found in commercial piezoelectric elements. In addition, a nine-layer thin film stack was fabricated by spin coating onto platinized silicon substrates. The films were crack-free and showed a perovskite grain structure with a weak (111) orientation. Piezoelectric measurements of the film showed a piezoelectric coefficient comparable to literature values and good stability toward fatigue.

Bottom-up water-based solution synthesis for a large MoS2 atomic layer for thin-film transistor applications

A bottom-up water-based solution-process method was developed for atomic layered MoS2 with a one-step annealing process and no sulfurization. The chosen MoS2 precursor is water soluble and was carefully formulated to obtain good coating properties on a silicon substrate. The coated precursor was annealed in a furnace one time to crystallize it. This method can obtain a large and uniform atomic layer of 2D MoS2 with 2H lattice structure. The number of atomic layers (4–7) was controlled through the precursor concentrations and showed good uniformity, which was confirmed by STEM and AFM. Four types of thin-film transistors (TFTs) were prepared from the solution-processed MoS2 on Al2O3 and SiO2 dielectric with either thermal evaporated Al or printed Ag source and drain electrodes. The best result shows an improved mobility of 8.5 cm2 V−1 s−1 and a reasonable on–off ratio of about 1.0 × 105 with solid output saturation.