The first solid-supported directed aromatic C–H activation/acetoxylation has been successfully developed by using palladium nanoparticles supported on graphene oxide (PdNPs/GO) as a catalyst. The practicability of this method is demonstrated by simple preparation of catalyst, high catalytic efficiency, wide functional group tolerance, and easy scale up of the reaction. A hot filtration test and Hg(0) poisoning test indicate the heterogeneous nature of the catalytic active species.

NiFe2O4 porous nanorods/graphene composites are synthesized by a solvothermal method in combination with calcination at 400 °C. Uniform NiFe2O4 porous nanorods with a diameter of about 300 nm and a length of several micrometers are homogeneously anchored on graphene sheets. The close and firm contact between the two components assures the sound electrochemical properties. The lithium-ion battery performance of the composites anode is evaluated by galvanostatic and rate performance. NiFe2O4 porous nanorods/graphene composites electrode exhibit a superior lithium storage capability. The first discharge capacity of the composites electrode is 1115 mA h g−1 at a current density of 1 A g−1, and still maintains at 655 mA h g−1 even after 600 cycles. Even at a high current density of 5 A g−1, a high reversible specific capacity of 509 mA h g−1 can be achieved. The synergistic effect between graphene with excellent electrical conductivity and NiFe2O4 nanorods with porous structure makes a substantial contribution to the outstanding electrochemical performance.

•Direct and autocatalytic ionic cyclization mechanism of copolymers of acrylonitrile-itaconic acid P(AN-IA) were compared using density functional theory (DFT) at B3LYP/6-31+G (d, p) level.•The free energy barriers of the cyclization reaction were hugely lowered by including a nearby P(AN-IA) copolymer serving as a catalyst.•The calculated free energy barrier of cyclization is about 22.74 kcal mol−1, which is in good agreement with the experimental activation barrier of 26.1 kcal mol−1.The direct and autocatalytic ionic cyclization mechanism of copolymers of acrylonitrile-itaconic acid P(AN-IA) have been studied using density functional theory (DFT) at B3LYP/6-31+G (d, p) level, respectively. By comparing the direct mechanism with autocatalytic mechanism, it was found that the free energy barriers of the cyclization reaction were hugely lowered by including a nearby P(AN-IA) copolymer serving as a catalyst. The calculated free energy barrier of cyclization is about 22.74 kcal mol−1, which is in good agreement with the experimental activation barrier of 26.1 kcal mol−1. The cyclization of P(AN-IA) would proceed by rather an autocatalytic mechanism than a direct mechanism.Download high-res image (54KB)Download full-size image

Traditional methods for the preparation of carbon aerogels, such as a sol–gel method, hydrothermal method, freeze-drying method and the direct carbonization of biomass materials, have been more and more limited in their applications due to their high cost, complex processes and the accompanying volume shrinkage in the preparation process. In this paper, we developed a novel air-expansion method for the preparation of porous carbonaceous aerogels with hierarchically macroporous, mesoporous and microporous structures from rice. The main advantages of an air-expansion method are large-scale preparation, low cost, a simple technique and most importantly it keeps the initial shape/structure and avoids shrinkage of the carbon aerogels owing to the air-expansion process of rice generating many macroporous structures for supporting the aerogel framework. When used as an anode for lithium ion batteries, rice-based carbonaceous aerogels exhibit a superior specific capacity and possess a good rate capability. This study gives a better insight into the preparation of carbonaceous aerogels from other grains as well as their potential applications in lithium ion batteries.

Highly branched sulfonated poly(arylene ether ketone)s (BSPAEKs) exhibit excellent potential as proton exchange membranes (PEMs). However, the mechanical properties of the branched membranes must be further improved. In this work, a series of BSPAEK-based composite membranes containing different amounts of polyacrylonitrile (PAN) were fabricated as PEMs. The expected ionic cross-linking and hydrogen bonding between BSPAEK and PAN was confirmed by Fourier transform infrared spectroscopy. The tensile strengths of the composite membranes with PAN contents from 5 to 20 % ranged from 16.4 to 23.0 MPa, which were notably higher than that of the BSPAEK membrane (13.1 MPa). Furthermore, the oxidative stability of the composite membranes was enhanced significantly from 295 to 430 min (2 ppm FeSO4 in 3 % H2O2) with increased PAN doping. Although the proton conductivity of the composite membrane was lower than that of BSPAEK, the proton conductivity of the composite membranes was still above 10−2 S cm−1 and satisfied the requirement of the fuel cells. The results indicate that this material is a suitable candidate PEM for evaluation in fuel cell applications.

•UHMWPE pre-stretched fibers were examined by in situ SAXS/WAXD during the ultra-high stretching process.•We reported the transition from shish-kebab to fibrillar morphology crystals of UHMWPE fibers.•There still exist chain conformation defects even in the majorly fibrillar morphology crystals.The ultra-high hot stretching was conducted on four-times pre-stretched ultra-high molecular weight polyethylene (UHMWPE) fibers to the ratio of about 508% to achieve the total ultra-high stretching ratio of about 2000%. In situ small and wide-angle X-ray scattering (SAXS/WAXS) measurements using synchrotron radiation and Raman spectroscopy were applied to study the structural evolutions of ultra-high stretched fibers. SAXS images revealed the transition from shish-kebab to fibrillar crystals, which is believed to involve with the increasing trans-configuration ratio of C–C backbone. WAXS results demonstrate the further stretching could still be applied to the fibers to acquire the complete extended-chain crystals.