Bing Na

Nanocellulose-mediated hybrid polyaniline electrodes for high performance flexible supercapacitors

Cellulose, abundant in nature, is very attractive for application in energy storage devices. Herein, cellulose nanofibers (CNF), detached from natural cellulose, are employed to fabricate flexible electrodes with polyaniline (PANI) as the active material for high performance supercapacitors. The presence of CNF in conductive composite substrates can tailor the morphology and doping of grown PANI worm-like nanorods during in situ polymerization, resulting in the improvement of specific capacitance. A maximum specific capacitance of 421.5 F g−1 is achieved for hybrid PANI electrodes based on composite substrates with 20 wt% CNF loading at a current density of 1 A g−1. Moreover, good rate capability and energy/power density balance are exhibited by the hybrid PANI electrodes. All-solid-state supercapacitors assembled from the hybrid PANI electrodes show excellent electrochemical performance and capacitance retention under repeated bending over 1000 cycles due to the mechanical flexibility of composite substrates with CNF as binders. This research provides a facile route to fabricate high performance flexible supercapacitors from bio-sourced CNF and low-cost PANI.

Effect of thermal treatment of Pd decorated Fe/C nanocatalysts on their catalytic performance for formic acid oxidation

The thermal treatment of bimetallic nanocatalysts plays an important role in determining their catalytic performance. Here tuning the surface oxidized metal species of bimetallic Pd–Fe electrocatalysts for the formic acid (FA) oxidation reaction is reported and a correlation between the surface oxidized metal species of the Pd–Fe nanoparticles and their catalytic activities is proposed. The structural details of the Pd–Fe/C catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy and high-sensitivity low-energy ion scattering (HS-LEIS). Cyclic voltammetry measurements demonstrated that the mass activity of the Pd–Fe nanoparticles with a molar ratio of Pd/Fe = 1/15 is about 7.4 times higher than that of Pd/C. This enhancement could be attributed to the synergistic effect between Pd(0) and Pd oxidized species on the surface of the Pd–Fe/C treated sample and electronic effects. This finding demonstrates the importance of surface oxidized metal species at the nanoscale in harnessing the true electrocatalytic potential of bimetallic nanoparticles and opens up strategies for the development of highly active bimetallic nanoparticles for electrochemical energy conversion.

Crystal structures and phase transformation of two novel solvates of valnemulin hydrochloride

Two novel solvates of valnemulin hydrochloride (VH), one is valnemulin hydrochloride water–ethanol solvate (VHWES) and the other is valnemulin hydrochloride water–methanol solvate (VHWMS), were first crystallized successfully. The structural and spectral characteristics of VHWES and VHWMS were studied by single crystal X-ray diffraction (SCXRD), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. It was found that both solvates crystallized in the monoclinic system with a P2 space group, and comprised protonated ammonium moieties, hydrochloride anions, water molecules and solvent molecules (ethanol or methanol) which are held together by a number of hydrogen bonds. The thermal characterization of VHWES and VHWMS was conducted through DSC/TG analysis. The results indicated that both of them would undergo a solvent loss over a certain temperature range, and then return to their original amorphous form. The solution-mediated phase transformation from VH to VHWES was in situ investigated by using PVM and Raman spectroscopy, and the kinetic parameters of the transformation process were also determined. It was found that the nucleation of VHWES was the limiting step of the transformation process, and the transformation rate accelerated with increasing temperature.

Formation of Ring-Banded Spherulites of Poly (L-lactide) in its Miscible Mixture with an Ionic Liquid

ABSTRACT Incorporation of an ionic liquid, nonvolatile and thermally stable, promoted formation of ring-banded spherulites in poly (l-lactide) (PLLA) during its sol–gel transition. Their formation is correlated with low viscosity and insignificant chain entanglements in the mixtures induced by the ionic liquid. In addition to a driving force for lamellar twisting that depended on the crystallization temperatures, it is believed that reduced lamellar twisting resistance caused by the ionic liquid plays a vital role in the formation of the ring-banded spherulites of PLLA from the mixtures. This study gives further insights into the structural formation of PLLA during a sol–gel transition, which could open new opportunities to tailor the properties of ion gels based on PLLA.