Electric double layer capacitors (EDLC) as electrical energy storage devices have many advantages over traditional electrolytic capacitors, including short charging time, wide operating temperature, long life, high energy density and so on. However, the specific capacity of EDLCs is many orders of magnitude lower than that of traditional batteries, which seriously restricts their application and development. EDLCs store energy by accumulating positive and negative charges of the electrolyte on the electrode surface. Therefore, expanding the specific surface area of ​​the electrode is the key to obtaining a high specific capacitance capacitor.
Today ’s world is most directly related to the birth and development of nanotechnology, and is known as the “initiating the industrial revolution†carbon nanotubes (Carbon nanotubes, CNTs) and graphene (grapheme) and other graphite carbon nanomaterials, due to low cost, Large specific surface area and good electrical conductivity are widely used in the manufacture of EDLC electrodes to increase their specific capacitance. Among them, the well-known graphene is a hexagonal two-dimensional planar thin film composed of a single layer of carbon atoms and sp2 hybrid orbitals. Its specific surface area is as high as 2630m2g-1, making it an ideal material for preparing supercapacitor electrodes.
A large number of studies have used low-cost graphene oxide (GO) to prepare EDLCs, including chemical reduction GO, thermal reduction GO, etc., showing that their specific capacitances are all higher than 100F / g. Electrochemical reduction is called "green reduction" because it can be carried out at normal temperature and does not require dangerous chemical reagents. In recent years, there have been attempts to use electrochemical reduction to reduce GO. However, the relationship between the electrochemical reduction process and the specific capacitance of GO capacitors has not yet been clarified.
Researcher Yu Hongwen of the Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Sciences and Japanese scientists jointly studied the effect of the electrochemical reduction process on graphene capacitors. They found that electrochemical reduction of graphene is the key to the preparation of electric double-layer capacitor electrodes that are only a few hundred nanometers thick. The electrodes prepared by pre-reduction at scanning potentials of -1.0-1.6V, -1.5-0V, and -1.0-1.0V Will show a completely different specific capacitance. They applied a -1.0-1.0V potential to reduce graphene oxide after 4000 seconds of scanning to obtain a new type of capacitive electrode with a specific capacitance of up to 246F / g. At the same time, they also studied and explored the remaining oxygen functional groups and residual oxygen on graphene The effect of the sp2 domain on the performance of the capacitor.
This research provides a theoretical basis for the breakthrough of high specific capacitance capacitors. Related research results were published in Carbon (51 (2013) 94 – 101).
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