Researchers in China have discovered a new method to convert fallen tree leaves into a porous carbon material that can be used to produce high-tech electronics.
In a study published in the Journal of Renewable and Sustainable Energy, the researchers described the process to convert tree leaves into a form that could be incorporated into electrodes as active materials.
The dried leaves were first ground into a powder, then heated to 220 degrees Celsius for 12 hours. This produced a powder composed of tiny carbon microspheres.
These microspheres were then treated with a solution of potassium hydroxide and heated by increasing the temperature in a series of jumps from 450 to 800 degrees Celsius.
The chemical treatment corrodes the surface of the carbon microspheres, making them extremely porous.
The final product, a black carbon powder, has a very high surface area due to the presence of many tiny pores that have been chemically etched on the surface of the microspheres.
The high surface area gives the final product its extraordinary electrical properties.
The investigators, led by Hongfang Ma of Qilu University of Technology in Shandong, ran a series of standard electrochemical tests on the porous microspheres to quantify their potential for use in electronic devices.
The current-voltage curves for these materials indicated that the substance could make an excellent capacitor.
Further tests showed that the materials were, in fact, supercapacitors, with specific capacitances of 367 Farads/gram, which are over three times higher than values seen in some graphene supercapacitors.
A capacitor is a widely used electrical component that stores energy by holding a charge on two conductors, separated from each other by an insulator.
Supercapacitors can typically store 10-100 times as much energy as an ordinary capacitor, and can accept and deliver charges much faster than a typical rechargeable battery.
For these reasons, supercapacitive materials hold great promise for a wide variety of energy storage needs, particularly in computer technology and hybrid or electric vehicles.