A team of scientists at Stanford University has figured out a way to use nanotechnology to develop a designer version of carbon.
This new version of carbon is not just versatile, but also "tunable," allowing scientists to change its pore size for whatever usage is required of the carbon.
The implications of this new carbon are great, because it could change the way batteries and supercapacitors store energy. This means more efficient batteries that store energy longer. However, this carbon could also find other common uses, such as in water filters and even air deodorizers.
Currently, scientists generally make activated carbon from coconut shells. They burn the shells at high temperatures and then treat it with chemicals. This creates tiny pores in the carbon, where chemical reactions happen and where the carbon stores energy.
This method is inexpensive, but has drawbacks. The pores can't carry electricity. The coconut shells also contain impurities that get into the carbon, affecting how efficient it is. In other words, it's a cheap method that doesn't really work all that well.
"Producing high-surface-area carbons with controlled chemical composition and morphology is really challenging," says Zhenan Bao, senior author of the study, which appeared in the journal ACS Central Science. "There are other methods currently available, but they're either quite expensive or they don't offer control over the chemical structure and morphology."
However, the new designer carbon has pores that are controllable, allowing scientists to adjust them for whatever purpose the carbon needs. They created their own version by baking hydrogel (a watery polymer) and activating it with potassium hydroxide. This creates a sheet of carbon thinner than the size of a human hair with 3D pores covering its surface.
What sets this method apart, though, is that based on temperature and chemical composition, scientists can control the size and quantity of the pores. This makes the material useful in a variety of applications, including batteries, supercapacitors and filters.
The Stanford researchers tested this carbon on lithium-sulfur batteries, which are generally better at energy storage than lithium-ion batteries, but have a problem with leaking. Using the designer carbon on those batteries, however, prevents that. They also tested their carbon with supercapacitors, finding that the designer carbon gave supercapacitors three times more electrical conductivity than those using standard activated carbon. "We also found that our designer carbon improved the rate of power delivery and the stability of the electrodes," Bao added.
Researchers also see this designer carbon used for carbon capture systems, which captures waste carbon dioxide, transporting it and depositing it somewhere safe where it won't enter the atmosphere.