Hemp Carbons Make Supercapacitors Superfast

Lots of products come to mind when discussing the many applications of hemp — beauty creams, food, fabrics, construction materials and even skate decks and surf boards — but making electric supercapacitors usually isn’t one of them. Apparently that’s going to change. 

Canadian researchers developed a way to convert fibrous hemp waste into nanomaterial, and they tested this hemp carbon in supercapacitors. The results, published in the ACS Nano journal in 2013, showed that hemp-based supercapacitors outperformed standard supercapacitors by nearly 200 percent. In describing the hemp-based nanosheets, the researchers used glowing terms like “remarkable” and “excellent” and said its characteristics place it “among the best power–energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor.” 

Better performance usually comes at a higher price, but in this case, the hemp nanosheets are significantly less expensive than the standard material, graphene. 

“We’re making graphene-like materials for a thousandth of the price, and we’re doing it with [hemp] waste,” said study author Dr. David Mitlin while presenting the work at an American Chemical Society (ACS) conference. 

For the non-gear heads among us, a supercapacitor (or ultracapacitor) is a high-capacity device that stores electrical energy and delivers charges at a much faster rate than batteries. Electricity enters or leaves the supercapacitor through electrodes, and graphene is one of the main materials for making these energy conductors. The price of graphene reportedly ranges between $67,000 and $200,000 per ton, while hemp biowaste checks in at between $100 and $1,000 per ton. At the ACS conference, Dr. Mitlin admitted that hemp can’t do all the things that graphene can, but “it works just as well” for energy storage. 

Additional studies have sought to make hemp carbon even better. For example, University of Kentucky researchers published findings in 2016 about the best ways to make hemp carbon nanosheets (e.g., hemp hurd performs better than hemp bast). They too achieved “excellent electrochemical performance metrics” with the hemp-based supercapacitor. More recently, researchers in Shanghai suggested other adjustments to improve performance in a 2020 study in Materials & Design

In the years since the publication of his 2013 study, Dr. Mitlin took his research to Clarkson University in New York before eventually joining the University of Texas at Austin. His battery-research team, the Mitlin Group, continues to explore alternative energy sources and (sometimes shocking) ways to preserve the environment. From hemp storage devices to batteries, Dr. Mitlin’s work is finding its way to market, and the planet is literally better for it. 

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