Activated Carbon Derived from Hemp and Its Use in Electrochemical Capacitors
In this study, the entire raw hemp stem is taken into full use; both bast (the outside fibrous part of the stem) and hurd (inside pulp of the stem) were prepared into high-performance activated carbons for electrochemical capacitors. Various processing factors were found to play important roles in the morphology, surface properties and electrochemical performance of the activated carbons, i.e. hydrothermal solution, pre-hydrothermal treatment, ratio of KOH/carbon, activation temperatures, etc. Using a systematic study of the preparation conditions, we are able to control the properties of the activated carbons and achieve excellent performance when used as electrode materials in electrochemical capacitors. This simple processing route presents great potential for preparing energy storage materials from raw biomass.
In this work, activated carbonaceous materials were prepared through hydrothermal and chemical activation processes using raw hemp as the precursor. Activated carbon materials having high surface area and high mesoporosity, perform well as active electrode materials in electrochemical capacitors (Figures 1a and 1b). In each case, the hemp (hurd) biochar was prepared by a hydrothermal process at 200 oC for 24h in 1 wgt % H2SO4. The resulting biochar was then activated with KOH at 800 oC for 1h.
Figure 1a. Cyclic voltammograms of KOH activated carbons prepared from hemp (hurd). The electrolyte is 1.8M TEMABF4/PC. Figure 1b. Charge/discharge curves of KOH activated carbons prepared from hemp (hurd) at different current densities. The electrolyte is 1.8M TEMABF4/PC.
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