No abstract

Very high surface area activated carbons (AC) are synthesized from pine cone petals by a chemical activation process and subsequently evaluated as an electrode material for supercapacitor applications in a nonaqueous medium. The maximum specific surface area of ∼3950 m(2)  g(-1) is noted for the material treated with a 1:5 ratio of KOH to pine cone petals (PCC5), which is much higher than that reported for carbonaceous materials derived from various other biomass precursors. A symmetric supercapacitor is fabricated with PCC5 electrodes, and the results showed enhanced supercapacitive behavior with the highest energy density of ∼61 Wh kg(-1). Furthermore, outstanding cycling ability is evidenced for such a configuration, and ∼90 % of the initial specific capacitance after 20,000 cycles under harsh conditions was observed. This result revealed that the pine-cone-derived high-surface-area AC can be used effectively as a promising electrode material to construct high-energy-density supercapacitors.

Here, we investigate the doping effects on the lithium ion transport behavior in garnet Li7La3Zr2O12 (LLZO) from the combined experimental and theoretical approach. The concentration of Li ion vacancy generated by the inclusion of aliovalent dopants such as Al3+ plays a key role in stabilizing the cubic LLZO. However, it is found that the site preference of Al in 24d position hinders the three dimensionally connected Li ion movement when heavily doped according to the structural refinement and the DFT calculations. In this report, we demonstrate that the multi-doping using additional Ta dopants into the Al-doped LLZO shifts the most energetically favorable sites of Al in the crystal structure from 24d to 96 h Li site, thereby providing more open space for Li ion transport. As a result of these synergistic effects, the multi-doped LLZO shows about three times higher ionic conductivity of 6.14 × 10−4 S cm−1 than that of the singly-doped LLZO with a much less efforts in stabilizing cubic phases in the synthetic condition.

We report the synthesis of two dimensional (2D) Co 3 S 4 in nano thickness sheet-like morphology via simple hydrothermal process and its application towards electrochemical energy storage devices. Presence of unique mesopores with combination of core/shell nanoparticles in the nanosheets showed superior electrochemical performances as negative electrode for Li-ion (LIB) and electro-catalyst in Li-O 2 battery applications. High discharge capacity of ~968 mAh g -1 is noted after 60 cycles with excellent cycling stability when evaluated as anode for LIB. On the other hand, first discharge capacity of ~5917 mAh g -1 is observed with high reversibility of 95.72% for Li-O 2 battery point of view. This exceptional electrochemical performance in both applications is mainly attributed to the presence of mesoporous with core/shell 2D nanostructure, which translates more catalytic bi-functional (oxygen reduction reaction/oxygen evolution reaction) active sites for Li-O 2 and sustains the volume variations occurred in 3D way upon charge/discharge process for LIB applications. Ex-situ studies, like TEM, XPS and impedance spectroscopy are also carried out to validate the reaction mechanisms.

Applicability and productivity of new click chemistry that exploits a nitrile N-oxide as a 1,3-dipole in polymer synthesis were demonstrated by the polymerization of diynes with a homo ditopic aromatic nitrile N-oxide. The nitrile N-oxide was synthesized in situ by the reaction of the corresponding hydroxamoyl chloride with molecular sieves 4 Å. The click polymerization of various ditopic diynes and the nitrile N-oxide efficiently produced polyisoxazoles in high yields. The homo ditopic nitrile N-oxide was also useful for the connection of bisacetylene-terminated polymers to give multiblock copolymers in very high yield. The resulting polyisoxazoles agree well with the structural assignment obtained by the 1H and 13C NMR analyses. The generated polyisoxazoles showed improved thermal stability due to the presence of isoxazole moieties. The molecular diversity of the obtained polyisoxazoles was confirmed by the selective transformations of the isoxazole moieties into β-aminoenone or β-aminoalcohol moieties with high conversion rates. The thermal decomposition temperature of the transformed polymers was lower than that of the polyisoxazoles because of the formations of abundant amino and hydroxyl groups. Furthermore, the functionality of poly(β-aminoalcohol) was proven by quantitatively cross-linking the polymers by treatment with terephthalaldehyde or methylene diphenyl diisocyanate.