The Synthesis and Characterization of Bioactive Carbon Material Supercapacitor Loaded with Nickel Hydroxide
Supercapacitor is an environmentally friendly energy storage device, which fills the gap between traditional capacitors and batteries, and its energy density and power density are higher than the battery [1]. Moreover, the supercapacitor has the characteristics of high charging and discharging efficiency and long cycle life. This makes it used in the electric vehicles, high powered weapons, standby power in electronic equipment, flash of industrial equipment and ignition device [2]. So it has great significance for the basic research, the development of electronic industry and the electric vehicle to carry out the supercapacitor electrode materials [3]. Here, we firstly prepared the activated carbon materials by carbonizing, activating the biological material, then prepared the nickel hydroxide/activated carbon composites by direct precipitation method, and studied the electrochemical properties of composite materials with different nickel hydroxide (Ni(OH)2) contents (the mass fraction). The results of cyclic voltammetry and constant current charge-discharge are that a small amount of Ni(OH)2 are mixed in the carbon surface and pores, the composite material has a good specific capacitance, stability, charging and discharging performance compared with the activated carbon. When the mass fraction of Ni(OH)2 is 12%, the supercapacitor exhibits the excellent electrochemical properties, its capacitance is up to 400.78F/g which improved 75.21% compared with the activated carbon’s capacitance (228.74F/g). 6mol/L potassium hydroxide (KOH) is used as an electrolyte, the capacitance is only reduced to 94.42% after conducting 1000 times cycle life tests. This means that the supercapacitor shows a good stability.
Research progress of electrolytes in supercapacitors
This review provides a brief summary of recent research progress in currently available electrolytes,including aqueous electrolytes,organic electrolytes,ionic liquids,solid electrolytes and redox electrolytes for supercapacitor,as well as corresponding important theories and technologies.The performance comparison among aqueous electrolytes,organic electrolytes and ionic liquids as supercapacitor electrolyte was conducted,and the capacitor self-discharge caused by shuttle effect of impure ion was also discussed.It indicates that the investigation on low-viscosity,high-conductivity and high electrochemical stability ionic liquid electrolyte is very important fundamental research and such electrolyte is expected to be the substitute for organic electrolytes.Additionally,the combination and optimization of ionic liquid and organic solvents mixture for supercapacitor electrolyte also represent an application trend in the future.
l-Phenylalanine dehydrogenase from Brevibacterium sp. for production of l-phenylalanine by reductive amination of phenylpyruvate
SummaryFor production of l-phenylalanine the reductive amination of phenylpyruvate, catalyzed by phenylalanine-dehydrogenase was examined. To reach high levels and a sufficient stability of the inducible intracellular enzyme, growth conditions of Brevibacterium sp. are optimized. For continuous production of l-phenylalanine in an enzyme membrane reactor, the kinetic parameters of the partially purified enzyme are determined.In continuous production a space time yield of 37.4 g l-Phe l-1 d-1 can be reached.By means of the measured kinetic parameters and simultaneous calculation of the mass balances of all reaction components the behaviour of the reactor can be simulated. For certain conditions the multi-enzyme-system shows multiple steady-states.