Polypyrrole shell@3D-Ni metal core structured electrodes for high-performance supercapacitors.

Three-dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high-performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D-Ni-core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as-prepared material exhibits a high specific capacitance (726 F g(-1) at a charge/discharge rate of 1 A g(-1)), good rate capability (a decay of 33% in Csp with charge/discharge rates increasing from 1 to 20 A g(-1)), and high cycle stability (only a small decrease of 4.2% in Csp after 1000 cycles at a scan rate of 100 mV s(-1)). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as-prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg(-1)) and superior long-term cycle ability (only 4.4% and 18.6% loss in Csp after 2000 and 5000 cycles, respectively).

[Mass Transport in Porous Sediments During a Turbulent Disturbance].

To examine mass transport in porous sediments during a turbulent flow, we established a simple sediment re-suspension device, made use of different sizes of sands as homogeneous sediments, and we injected 500 µg x cm(-3) soluble Rhodamine B into different parts of the sediment as the mass tracer, to observe mass transport during the turbulent condition. The research showed that in porous sediments, pore-water pressure difference would be generated because of the sediments' distinctive porosity and permeability, and further led to the convective flow and mass transport in porous media. Moreover, such mass transport was directly influenced by its burial depth and particle size of the sediment. While in homogeneous sediments, mass transport was strongly influenced in vertical direction under 200 r x min(-1) disturbance, and when moderately increased the size of porous particles under the same turbulent condition, such convection of pore-water would relatively enhance.