Porous carbon nanosheets help high capacity supercapacitors

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.

Summary of results:

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 published in the full text of the ACS Applied materials Interfaces entitled "Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors" and was accepted by the Chemical Engineering News. Popcorn's perfect pores publishes a news report for the title. Dr. Hou Jianhua said that the work was inspired by the question when her daughter was eating popcorn: Why popcorn would be so crispy? This led Dr. Hou Jianhua to think about how the microstructure from corn to popcorn changed.

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 and the ionic liquid electrolyte, respectively, and the highest energy density and excellent rate performance in the biomass carbon material were obtained. This is mainly due to the following characteristics:

(1) PCF-X ultra-high specific surface area (such as PCF-900 has a specific surface area of up to 3301 m2•g-1) to provide a large number of active sites for electrochemical reactions;

(2) High microporous ratio (PCF-900 micropore surface area accounts for 95% of the total specific surface area, especially the microporous (1 nm) surface area reaches 1550 m2 g-1, and there is an optimal pore with a size of 0.69 nm. The ion desolvation process caused by its "microporous effect" greatly increases the specific capacity (capacity up to 311 F•g-1 at a current density of 10 A•g-1). In addition, the low pore volume and high specific surface area of PCF-X greatly enhance the volumetric energy density (103 Wh•kg-1), indicating that microporous-dominated materials have great potential for application in supercapacitors.