Skip to main content

Team finds electricity can be generated by dragging saltwater over graphene

Team in China finds electricity can be generated by dragging saltwater over graphene
Illustration of the experimental set-up. A liquid droplet is sandwiched between graphene and a SiO2/Si wafer, and drawn by the wafer at specific velocities. Inset: a droplet of 0.6 M NaCl solution on a graphene surface with advancing and …more
(Phys.org) —A team of researchers at China's Nanjing University of Aeronautics and Astronautics, studying graphene properties, has discovered that the act of dragging saltwater over a piece of graphene can generate electricity. In their paper published in the journal Nature Nanotechnology, the team describes how in seeking to turn the idea of submerging carbon nanotubes in a flowing liquid to generate a voltage on its head, they came upon the idea of simply dragging water droplets across graphene instead.
Because of 's unique electrical properties, researchers have been hard at work trying to determine if it can be used to generate electricity at a lower cost (and in cleaner fashion) than conventional methods. To date, scientists have been using a technique whereby ionic fluids are pushed through different types of nanostructures—it works, but a  must be used, which causes the approach to be inefficient. Others have looked at putting carbon nanotubes in moving water to capture electricity that is generated, but once again, a pressure gradient is needed. In this new effort, the researchers have found a way to generate electricity using graphene without the need for a pressure gradient, or any other mechanism other than gravity.
In their experiments, the researchers placed single drops of sea water (and other ionic solutions) on top of strips of monolayer graphene and then dragged them around. Doing so, they discovered, resulted in the generation of electricity—adding more drops or increasing the velocity of dragging increased the voltage.
To understand why, the team took a closer look. As it turned, out, the explanation was simple. When a saltwater drop sits still on top of a strip of graphene, any charge is redistributed symmetrically on both sides of the drop, leaving zero net potential difference between them. When the drop is moved, however, the distribution becomes unbalanced—electrons are desorbed at one end of the drop and absorbed at the other, generating a small amount of voltage—just 30mV—enough to allow the team to use it as part of a handwriting sensor and as part of an energy harvesting device.
Using the newly discovered technique to generate electricity isn't going to become a commercial proposition anytime soon, of course, as there is still the tricky problem of creating mass amounts of graphene at a reasonable price. But if that ever happens, people everywhere could very easily create their own , as it appears the process is exceptionally scalable.
More information: Generating electricity by moving a droplet of ionic liquid along graphene, Nature Nanotechnology (2014) DOI: 10.1038/nnano.2014.56
Abstract
Since the early nineteenth century, it has been known that an electric potential can be generated by driving an ionic liquid through fine channels or holes under a pressure gradient. More recently, it has been reported that carbon nanotubes can generate a voltage when immersed in flowing liquids, but the exact origin of these observations is unclear, and generating electricity without a pressure gradient remains a challenge. Here, we show that a voltage of a few millivolts can be produced by moving a droplet of sea water or ionic solution over a strip of monolayer graphene under ambient conditions. Through experiments and density functional theory calculations, we find that a pseudocapacitor is formed at the droplet/graphene interface, which is driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. This gives rise to an electric potential that is proportional to the velocity and number of droplets. The potential is also found to be dependent on the concentration and ionic species of the droplet, and decreases sharply with an increasing number of graphene layers. We illustrate the potential of this electrokinetic phenomenon by using it to create a handwriting sensor and an energy-harvesting device.


Comments

Popular posts from this blog

This strange mineral grows on dead bodies and turns them blue

If you were to get up close and personal with Ötzi the Iceman – the 5,000-year-old mummy of a  tattooed ,  deep-voiced  man who died and was frozen in the Alps – you’d notice that his skin is flecked with tiny bits of blue. At first, it would appear that these oddly bluish crystal formations embedded in his skin are from freezing to death or some other sort of trauma, but it’s actually a mineral called  vivianite  (or blue ironstone) and it happens to form quite often on corpses left in iron-rich environments. For Ötzi, the patches of vivianite are  from him resting  near rocks with flecks of iron in them, but other cases are way more severe. According to Chris Drudge at Atlas Obscura , a man named John White was buried in a cast iron coffin back in 1861. During those days, coffins often had a window for grieving family members to peer inside even if the lid was closed during the funeral. Sometime after he was buried, that window broke, allow...

Where the Swastika Was Found 12,000 Years Before Hitler Made Us Uncomfortable About I

Minoan pottery from Crete. The Minoan civilization flourished from 3,000 to 1,100 B.C. (Agon S. Buchholz/Wikimedia Commons) ) Swastika from a 2nd century A.D. Roman mosaic. (Maciej Szczepańczyk/Wikimedia Commons A srivatsa (swastika) sign at Nata-dera Temple, Japan. (Cindy Drukier/Epoch Times) From the Sican/Lambayeque civilization in Peru, which flourished 750 to 1375 A.D. (Wikimedia Commons) Ancient Macedonian helmet with swastika marks, 350-325 B.C., found at Herculanum. (Cabinet des Medailles, Paris/Wikimedia Commons) A Buddha statue on Lantau Island, Hong Kong with a swastika symbol on the chest. (Shutterstock*) A 3,000-year-old necklace found in the Rasht Province of Iran. (Wikimedia Commons) The aviator Matilde Moisant(1878-1964) wearing a swastika medallion in 1912; the symbol was popular as a good luck charm with early aviators. (Wikimedia Commons) A mandala-like swastika, composed of Hebrew letters and surrounded by a circle and a mystica...

20,000 megawatts under the sea: Oceanic steam engines

Jules Verne mused about getting energy from heat in the ocean  (Image: Marc Pagani/Getty) Jules Verne imagined this limitless power source in Victorian times – now 21st-century engineers say heat trapped in the oceans could provide electricity for the world IF ANY energy source is worthy of the name "steampunk", it is surely ocean thermal energy conversion. Victorian-era science fiction? Check: Jules Verne mused about its potential in  Twenty Thousand Leagues Under the Sea  in 1870. Mechanical, vaguely 19th-century technology? Check. Compelling candidate for renewable energy in a post-apocalyptic future? Tick that box as well. Claims for it have certainly been grandiose. In theory, ocean thermal energy conversion (OTEC) could provide  4000 times the world's energy needs in any given year , with neither pollution nor greenhouse gases to show for it. In the real world, however, it has long been written off as impractical. This year, a surprising number of pro...