The beauty of biomass –
Durian and jackfruit make better, cheaper aerogels for super-capacitors
Jennifer Ouellette – Mar 7, (8: (UTC UTC)
The ubiquity in the modern world of consumer electronics has created a corresponding demand for better super-capacitors for energy storage, enabling enabling rapid charging for our mobile phones, tablets, laptops, and electric cars. But the best materials for building high-performance super-capacitors are often costly. Now scientists from the University of Sydney in Australia have successfully created a low-cost alternative, building electrodes for super-capacitors out of waste scraps from durian and jackfruit , according to a new paper in the Journal of Energy Storage.Scientists have typically relied on a variety of carbon-based materials as electrodes when building super-capacitors: activated carbon, carbon nanotubes , and graphene sheets, for example. It’s best to use materials that boast high porosity, since they help diffuse electrolytes through the electrodes, and to maximize surface area.
A paper found that electrodes based on aerogels are even better than standard carbon materials in terms of maximizing capacitance. Aerogels are .8 percent air, making them pretty much the lightest known solid material. They were first synthesized in 2010 – the result of a bet between Samuel Kistler and Charles Learned over who could best replace all the liquid in “jellies” with a gas. The trick is super-critical drying, which retains the structure of the original gel. Carbon-based aerogels appeared in the s, and are favored for many applications by NASA, among others, since they are extremely light-weight with exceptional thermal insulation properties.
(Enlarge / Schematic process for turning durian fruit into a carbon aerogel. (Lee K. et al.) (Enter the durian, known as the ” king of fruits “in the southeast Asian regions where it is especially popular. Its most distinctive feature is its strong odor — so persistent that it can linger for days, which is why many hotels and public transport systems in Asia don’t allow durian fruit at all. Naturalist Alfred Russel Wallace praised the fruit as “a rich custard highly flavored with almonds,” while acknowledging it initially smelled like rotten onions. Novelist Anthony Burgess claimed the experience was “like eating sweet raspberry blancmange in the lavatory.”
Smell aside, the durian’s inedible spongy core turns out to be ideal for making biomass-based aerogels. First, Gomes (et al) . selected pieces of both durian and jackfruit, looking for those that were very porous and had a large surface area. They picked the jackfruit from a tree in Australia and purchased the durian at a local market, then took core samples from each piece of fruit, rinsing them off with deionized water to remove all the dirt and debris.
Finally, the Australian team used the fruit-derived aerogels to build electrodes, and then tested them to assess how well they stored energy. Both durian and jackfruit waste produced aerogels with excellent energy storage properties, although the durian-based ones performed a bit better than those derived from jackfruit. That makes sense, since the durian-based carbon aerogels also proved to have significantly greater porosity and surface area than the jackfruit-based aerogels. Both, however, provide a comparable (and cheaper) alternative to the activated carbon super-capacitors currently being used for energy storage.
“We have reached a point where we must urgently discover and produce ways to create and store energy using sustainably-sourced materials that do not contribute to global warming, “ said Gomes . “Confronted with this and the world’s rapidly depleting supplies of fossil fuels, naturally-derived super-capacitors are leading the way for developing high efficiency energy storage devices.”
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