We report that CoNi2S4 nanosheet arrays exhibit ultrahigh specific capacitance of 2906 F g(-1) and areal capacitance of 6.39 F cm(-2) at a current density of 5 mA cm(-2), as well as good rate capability and cycling stability, and superior electrochemical performances with an energy density of 33.9 Wh kg(-1) at a power density of 409 W kg(-1) have been achieved in an assembled aqueous asymmetric supercapacitor. The CoNi2S4 nanosheet arrays were in situ grown on nickel foams by a facile two-step hydrothermal method. The formation mechanism of the CoNi2S4 nanosheet arrays was based on an anion-exchange reaction involving the pseudo Kirkendall effect. The two aqueous asymmetric supercapacitors in series using the CoNi2S4 nanosheet arrays as the positive electrodes can power four 3-mm-diameter red-light-emitting diodes. The outstanding supercapacitive performance of CoNi2S4 nanosheet arrays can be attributed to ravine-like nanosheet architectures with good mechanical and electrical contact, low crystallinity and good wettability without an annealing process, rich redox reactions, as well as high conductivity and transport rate for both electrolyte ions and electrons. Our results demonstrate that CoNi2S4 nanosheet arrays are promising electrode materials for supercapacitor applications.

Bio-based polyols from epoxidized soybean oil and castor oil fatty acid were developed using an environmentally friendly, solvent-free/catalyst-free method. The effects of the molar ratios of the carboxyl to the epoxy groups, reaction time, and reaction temperature on the polyols' structures were systematically studied. Subsequently, polyurethane films were prepared from these green polyols. Properties of the new, soy-castor oil based polyurethane films were compared with two other polyurethane films prepared from castor oil and methoxylated soybean oil polyol, respectively. Thermal and mechanical tests showed that the polyurethane films prepared from the new polyols exhibited higher glass transition temperatures, tensile strength, Young's modulus, and thermal stability because of the higher degree of cross-linking in the new polyols. Moreover, the novel polyols, prepared using the solvent-free and catalyst-free synthetic route, were 100% bio-based and facilitate a more environmentally friendly and economical process than conventional soy-based polyols used for polyurethane production.Footnotes † Electronic supplementary information (ESI) available. See

The catalytic effects of 1, 8-diazabicyclo[5.4.0]-undec-7-ene (DBU) and pyridine on the ring-opening reaction between epoxidized soybean oil and fatty acids from castor oil in a solvent free process were investigated using differential scanning calorimetry and were analyzed using both model-free and model-fitting methods. The resulting biopolyols from this reaction with epoxidized soybean oil, and similarly prepared polyols from epoxidized linseed oil, were characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. Polyurethane films were prepared by step-growth polymerization of the biopolyols with isophorone diisocyanate and were characterized by dynamic mechanical analysis, thermogravimetric analysis, and tensile tests. Polyurethanes from polyols manufactured with DBU as catalyst exhibited higher glass transition temperatures, tensile strength, and Young's modulus than polyurethanes from polyols manufactured using a catalyst-free method, which was attributed to the more homogeneous structure of their cross-linked network.

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