Hesheng Liu

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.

Critical Composition of the β Form of Poly(vinylidene fluoride) in Miscible Crystalline/Crystalline Blends

Crystallization and the polymorphic transition of poly(vinylidene fluoride) (PVDF) in its miscible blends with poly(butylene succinate) (PBS) from the melt has been investigated. The presence of a miscible PBS component lowers the crystallization temperature and the melting point of the PVDF component in the blends. It becomes more significant above a critical PBS content between 40 and 50 wt % where PVDF chains are dispersed in the matrix composed by PBS chains. On the other hand, the β form of the PVDF component can be induced at low temperatures, which also has a transition at the critical PBS content.

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.