In Indonesia it is customary to consume this tropical fruit called durian that smells deeply rotten. For some people it is the foulest food in the world. Such is its stench that even some hotels in Southeast Asia are forbidden. Its appearance, moreover, is not very pleasant: of considerable size (up to 30 centimetres), it has an elongated or rounded shape and is covered by thorns. In fact, its name comes from the Malay "duri", which means thorn.
However, this fruit would be able to charge the battery of a smartphone.
At least this is what Vincent G. Gomes, an associate professor at the University of Sydney and co-author of a new study describing a novel method of using durian biological waste to produce faster and more efficient electric chargers, has shown, the equivalent of a power-bank. His work was published in the Journal of Energy Storage in early 2020.
The secret of durian lies in the structural precision of natural biomass, with its strategically dispersed pores, which offers an exceptional resource as a template for the synthesis of carbon-based materials.
In a climate change scenario where there is also a rapid decline in fossil fuels, the adoption of supercapacitors to store energy with which to power, for example, devices or even vehicles, remains costly, which is why Gomes has resorted to relatively cheap organic waste, such as durian.
Conventional batteries have two electrodes, separated by an electrolyte, which is just a chemical that serves as a catalyst to cause a chemical reaction inside the battery. These reactions turn chemicals inside a battery into new substances that release electrical energy. Once all the chemicals inside have been exhausted, the processes stop and the battery runs out. Rechargeable batteries, on the other hand, allow internal chemical reactions to run in both directions, becoming cyclical in nature. That’s why the lithium-ion battery inside a smartphone, for example, can be charged and downloaded over and over again.
If a battery stores electrical energy in the form of chemical energy, a capacitor stores electrical energy in a magnetic field. Although capacitors are much less efficient than batteries, the advantage is that they do not use toxic metals and can be recharged almost infinitely.
Supercapacitors, however, would be more efficient. Supercapacitors are usually constructed with two sheets of metal that are coated with a material such as activated carbon, which functions as an electrode, creating a wider surface to store more cargo. The main supercapacitors are those that are made as aerogels, carbon nanotubes or activated carbon.
Gomes and the rest of his team then freeze the biomass of two fruits, both durian (Durio zibethinus) and jaca (Artocarpus heterophyllus), which transformed an extremely light and porous synthetic material into stable carbon aerogels. The current supercapacitors are made of activated carbon that are not as efficient as those prepared during this study, and those made of aerogels are derived from expensive and exotic graphene-based materials.
This project is a further step in the development of more efficient supercapacitors. Durian may become a more efficient and sustainable substitute for today’s plastic power-banks.
Reference: Kenny Lee, Luba Shabnam, Shaikh Nayeem Faisal, Van Chinh Hoang, Vincent G. Gomes, "Aerogel from fruit biowaste produces ultracapacitors with high energy density and stability", Journal of Energy Storage, Volume 27, 2020,101152, ISSN 2352-152X, https://doi.org/10.1016/j.est.2019.101152.