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The SEM morphology of ramie-based hollow activated carbon fibers was observed (a), specific surface area characterization results (b) and electrochemical performance test results (cd) (c: constant current charge and discharge test results; d: impedance performance test results).
Among the many active carbon materials used in supercapacitors, hollow activated carbon fibers are subject to advantages such as faster adsorption/desorption rate, smaller adsorption/desorption resistance, and larger adsorption capacity due to their special internal hollow structure. Researchers of various countries have paid attention to the fact that raw materials commonly used in the synthesis of hollow activated carbon fibers are non-renewable petroleum resources such as asphalt and phenolic resins, and require spinning, pre-carbonization, high temperature carbonization (800-1000°C), and activation steps. The preparation process is complex and cumbersome with high energy consumption.
In recent years, in order to reduce raw material costs and achieve environmental friendliness and sustainability of raw materials, a variety of rich, low-cost, renewable biomass materials have become a new direction for the preparation of porous activated carbon. However, under the condition of maintaining the special structure of natural biological materials, porous activated carbon materials with high energy storage performance still face great challenges.
Recently, a research team led by research fellows Qi Tao and Wang Yi of the Institute of Process Engineering of the Chinese Academy of Sciences found that the use of zinc chloride as an activator allows one-step carbonization activation of ramie fiber at low temperatures (400-650° C.). This method can obtain hollow carbon fibers with specific surface area over 2000 m2 g-1 and pore volume up to 1.08 cm3 g-1 on the premise of keeping the natural hollow structure of the raw materials.
A variety of electrochemical performance tests showed that the ramie-based hollow activated carbon fiber has a higher capacity (287Fg-1) and good electrochemical cycle stability. Due to the special hollow structure inside the material, the rate of adsorption and migration of the electrolyte inside the material is increased, and the resistance of the material is significantly reduced. The method for preparing the ramie-based hollow activated carbon fiber by the one-step zinc chloride carbonization activation method can not only shorten the production cycle of the porous activated carbon material, but also reduce the production energy consumption. The obtained product also has a good electrochemical energy storage performance, and therefore has a good application prospect.
The above related research has been funded by the Chinese Academy of Sciences 100-person plan and the National Natural Science Foundation of China (51302264). The research results were published in Bioresource Technology (2013, 102:31-37).
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