Researchers from South Korea have demonstrated how heat treatment can be used to convert discarded cigarette butts into a carbon-based material able to be integrated into devices such as computers, portable electronics, electrical cars and even wind turbines, and which could lead to new ways to store energy. Their study showed by treating the filters using a one-step process, the resulting material could store a higher amount of electrical energy than commercially available carbon, graphene and carbon nanotubes.
As reported in the journal Nanotechnology [Lee et al. Nanotechnology (2104) DOI: 10.1088/0957-4484/25/34/345601], cigarette filters, which are mostly composed of cellulose acetate fibers, were turned into a porous carbon-based material through a straightforward single-step burning technique known as pyrolysis. This process created tiny holes of different sizes in the material to increase its total surface area, with the material then used to coat electrodes of supercapacitors – electrochemical components that can store very large amounts of electrical energy – to increase its performance as a supercapacitive material.
“Numerous countries are developing strict regulations to avoid the trillions of toxic and non-biodegradable used cigarette filters that are disposed of into the environment each year; our method is just one way of achieving this.”Jongheop Yi
Supercapacitors are usually made of carbon as it is cheap and has high surface area and high electrical conductivity, as well as stability over the long term. As co-author Jongheop Yi, a professor from Seoul National University, said “A high-performing supercapacitor material should have a large surface area, which can be achieved by incorporating a large number of small pores into the material”.
The technique was tested in a three-electrode system to explore how effective it was in adsorbing electrolyte ions and then releasing them in a charge–discharge cycle. The material was seen to be capable of reproducing its electrochemical performance during the 6,000 cycles required for charge and discharge measurements. The unique self-developed pore structure allowed for electrolyte permeation and contact probability, resulting in the extended rate capability for the supercapacitor.
As well as helping to meet our ever-growing energy demands, the breakthrough also offers a solution to the environmental problem of dealing with such large amounts of used cigarette filters. With an estimated 5.6 trillion used cigarette filters thrown away every year, this is a major issue, especially as they can leach arsenic, lead and other chemicals into the environment. As Professor Yi added, “Numerous countries are developing strict regulations to avoid the trillions of toxic and non-biodegradable used cigarette filters that are disposed of into the environment each year; our method is just one way of achieving this.”