Porous carbon nanosheets help high capacity supercapacitors

【introduction】

The depletion of traditional fossil fuels such as coal, oil, and natural gas has forced people to develop renewable clean energy and matching energy storage and conversion devices. In electrochemical energy storage devices, electrode materials are a key factor affecting their performance. Porous carbon materials have become the most widely used electrode materials due to their controllable surface area, multi-dimensional complex pore structure, good electrical conductivity and low cost. The specific surface area (SSA), microstructure, and chemical composition of carbon materials are critical factors influencing the performance of energy storage devices such as supercapacitors. In particular, the controllable synthesis of the size and geometry of nanopores has become a focus of attention due to its strong influence on the energy density and power density of carbon-based supercapacitors.

[Introduction]

Recently, Dr. Hou Jianhua from Yangzhou University reported that popcorn-derived porous carbon nanosheets (PCF-X) obtained from biomass corn can greatly improve the performance of electrochemical energy storage devices. This important research in ACS Applied materials & Interfaces full text of a speech entitled "Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors" academic papers, and by the American Chemical Society (Chemical & Engineering News) to "popcorn's perfect pores (perfect hole popcorn)" in the title published news reports. Dr. Hou Jianhua said that the work was inspired by the question when her daughter was eating popcorn: Why is popcorn so crispy? This led Dr. Hou Jianhua to start thinking about how the microstructure of corn to popcorn changes.

Using corn as the raw material, the researchers used the "internal heating" mechanism of the microwave and the "expansion effect" caused by the rapid temperature rise for 2 minutes, and then the microwave was pre-carbonized for 8 minutes to obtain the honeycomb macrostructure carbon material, and then combined with alkali activation. The method successfully designed a porous carbon nanosheet with an ultra-high specific surface area dominated by micropores. The performance of the supercapacitor with PCF-X as the electrode material was tested in the aqueous electrolyte (Fig. 4) and the ionic liquid electrolyte (Fig. 5), respectively, and the highest energy density and excellent magnification in the biomass carbon material were obtained. performance. This is mainly due to the following characteristics: (1) PCF-X ultra-high specific surface area (such as the specific surface area of ​​PCF-900 up to 3301 m2·g-1) provides a large number of active sites for electrochemical reactions; (2) high micro aperture ratio (PCF-900 micropore surface area of ​​the total surface area of ​​95 (<1 nm)%, very especially micropore surface area reaches 1550 m2 g-1, and there is an optimal pore size of 0.69 nm), because ion "microporous effect" caused "desolvation" process greatly increases the specific capacity (at a current density of 10 a · g-1 when the capacity of up to 311 F · g-1). Further, the PCF-X low pore volume and high surface area active earth enhanced volumetric energy density (103 Wh · kg-1), indicates that the microporous material has led great potential supercapacitor.

[Graphic introduction]

Figure 1 Synthesis flow chart of PCFs

Figure 2 Micromorphology of popcorn, PCF and PCF-900

Figure 3 Structural characterization of PCF-X

FIG 4 PCF-X in a two-electrode system to the supercapacitor performance of the electrolytic solution 6 M KOH

Figure 5 Performance of PCF-X supercapacitor with EMITBF4 as electrolyte in two-electrode system

【summary】

The work of the group reported the successful design of a microporous-oriented porous carbon nanosheet (PCF-X) using a green, simple, and rapid method. The prepared PCF-X has a high micropore surface area (~1550 m2·g-1), and the ion desolvation process caused by its "microporous effect" greatly increases the specific capacity and is also obtained in the existing The highest energy density in biomass carbon materials studied. This work broadens the controllable synthesis of the size and geometry of nanopores that recognize carbon, suggesting that microporous-dominated carbon materials are also well suited for use in supercapacitors, increasing the practical potential of energy storage materials such as supercapacitors.