Reuse discarded plastic items and raise their economic value is now a popular assignment being undertaken at companies across different industries and research agencies worldwide. Recently, researchers at the University of California, Riverside (UCR) have discovered that the ubiquitous plastic bottles can be converted into carbon nanofibers for building supercapacitors, which are now becoming another highly sought-after form of energy storage. The potential for upcycling could strengthen the existing policies for the treatment of plastic waste and increase the appeal of recycling ordinary beverage bottles among consumers.
Supercapacitors are capacitors with a very high capacitance value and a different structural configuration compared with conventional capacitors. Versus batteries, all capacitors have the advantages of a shorter charge/discharge cycle, a higher power density, and a longer cycle life. Applications for supercapacitors range from scientific research to energy to transportation. The UCR team wants to increase the market attractiveness of supercapacitors by turning discarded plastic items into an advanced carbon material that can be used to build an environment-friendly electrostatic double-layer capacitor.
Researchers at UCR have been conducting studies on numerous subjects related to the environment and energies. Examples include the conversion of glass bottles and plastic toys into advanced materials for energy storage devices as well as the production of biofuels from fungi and plants. Mihri Ozkan, a professors of electrical engineering at UCR, said that the share of electric models in the global car fleet is forecasted to reach 30% by 2040. The widening adoption of electric vehicles will therefore drive up the demand for automotive batteries and capacitors. Ozkan pointed out that transforming plastic waste that is destined for landfills and recycling plants into structural materials for energy storage devices would represent an enormous breakthrough. Besides the cost-savings, there are other benefits such as the reduction of plastic pollution and the increase in the sustainability of the manufacturing process.
In developing low-cost materials for supercapacitors, the UCR team also wants to tackle the rapid growth of plastic pollution that is now becoming an environmental headache for many countries. The upcycling process designed by the UCR team involves first dissolving PET plastics from bottles, CDs, and polarizer films in a solvent and then drawing out fine threads from the solution through electrospinning. Afterwards, these fibers, which are nanometers in thickness, undergo carbonization in a furnace.
The carbon nanofibers are further coated with a binder and a conductive agent in order to formally become a structural material for an electrostatic double-layer capacitor. The UCR team stated that the testing on a button-like capacitor made from the PET-based carbon nanofibers showed great performance results that were in line with the team’s original expectation. Arash Mirjalili, first author of this study on PET-based carbon nanofibers, said that the team has “taken the first steps” in upcycling plastic waste into materials for rechargeable energy storage devices. Mirjalili further noted that the manufacturing process for the carbon nanofibers have significant environmental and economic benefits. All in all, the work done by the UCR team is expected to open up more R&D opportunities in the field of energy storage.
The UCR team is also looking at using plastic waste to build lithium-ion batteries. Although capacitors are faster than batteries in charging/discharging, they do not store as much energy for the same size. Therefore, even supercapacitors are not suitable for powering smartphones and the motors of electric vehicles. The two energy storage technologies have different application scopes. However, the UCR team believes that the carbon nanofibers that it has developed can be used to make electrode materials that improve the performance of lithium-ion batteries. Ozkan stated that the follow-up research will be working toward this goal.
(News source: TechNews. Photo credit: Pixabay.)