Stub, toss, out of sight. Cigarette butts are things people don’t give a second thought, but they are the most common plastic litter around the world. But researchers in China and England have now turned this ubiquitous waste into a key component of battery-like energy storage devices.
People consume over 5.8 trillion cigarettes globally every year, generating about 8 million tons of waste cigarette butts. Their outer packaging is made of cellulose, a plant-derived material, and the filter tip is made of cellulose acetate, a man-made plastic. Cigarette butts also contain harmful substances such as lead and heavy metals. The plastic filters can take up to 10 years to completely degrade, but the chemicals they release can linger in the environment.
Researchers have been trying to devise ways to reuse this waste. Leichang Cao of Henan University and colleagues identified cigarette butts as a low-cost, widely available carbon resource. Cigarette butts have a structure that makes them a promising starting point for making high quality porous carbon materials.
Such materials, with their very high surface area and ability to conduct charge, make excellent electrodes in energy storage devices. Specifically, devices called supercapacitors, which promise higher power output and faster charging than batteries.
The team came up with a two-step method to convert the toxic waste material into supercapacitor electrodes. First they heat wet cigarette butts at 700°C. This converts the waste into a char-like material that looks like it’s made of spherical carbon particles under the microscope.
Then the researchers treat the char with potassium hydroxide, which opens up the dense, smooth carbon spheres to create a porous network. During the process, nitrogen and oxygen are both introduced into the material, which evolves into a porous material with a 3D honeycomb-like structure with a huge surface area that allows ions and electrons to zip through.
Supercapacitors made with the material showed a high energy density of over 24 watt-hours per kilogram. This is higher than electrodes made from many biomass-derived and commercial activated carbon materials, the researchers write. They report their findings in the journal Energy & Environment Nexus.
Source: Jieni Wang et al. N,O co-doped hierarchical nanoporous biochar derived from waste cigarette butts for high-performance energy-storage application
Image: ©Anthropocene Magazine
