Skip to comments.Graphene battery demonstrated to power an LED
Posted on 03/16/2012 9:41:04 AM PDT by Red Badger
Scientists in Hong Kong have reported, in ArXiv, their experiments to make a graphene battery that they say generates an electrical current by drawing on the ambient thermal energy in the solution in which it is immersed.
Researchers led by Zihan Xu of the Department of Applied Physics and Materials Research Centre at the Hong Kong Polytechnic University, attached silver and gold electrodes to a graphene sheet, typically 7 mm x 7 mm in area, mounted on a silicon substrate. The assembly was then immersed in a saturated solution of copper chloride (CuCl2), and was found to produce an electrical voltage of 0.35 V. They also found that six assemblies arranged in series produced enough electricity to power a light-emitting diode (LED). The device continued to produce around the same voltage for 25 days, but after a month it dropped to about 40 mV.
Graphene is a material that consists of a layer of carbon only one atom thick, and it has been the subject of intense research in recent years because of its unusual properties. One of these properties is an exceptionally high electron mobility.
Xu and colleagues write in their paper that they think the voltage arises from the kinetic energy of the copper ions in the copper chloride solution, which they say is enough to knock electrons out of the graphene, and that these electrons then flow through the sheet. They noted that the voltage increases when the copper chloride solution is heated, and varies with its concentration.
The group also found the voltage increased when the assembly was exposed to pulses of ultrasound, and they say this lends weight to the idea that kinetic energy is the source of the voltage, since the ultrasound would increase the velocity of the copper ions. Small voltages were also produced with ionic solutions such as NaCl and CuSO4. The researchers also carried out control experiments to rule out the possibility that chemical reactions were responsible for the voltage generated.
Dr. Wanlin Guo, the graduate supervisor of one of Xus team (Guoan Tai), expressed skepticism at the proposed mechanism, and added that he had so far been unable to reproduce the findings in his own experiments, in which he used graphene sheets of varying sizes, mounted on varying substrates, and with different kinds of electrodes. He was unable to achieve voltages greater than around 0.1 mV.
In 2011, a research group led by Nikhil Koratkar of New Yorks Rensselaer Polytechnic Institute also reported on experiments in which graphene was shown to generate a voltage when an ionic solution was made to flow over the sheets. Dr. Guo, of Nanjing University in China, also refuted these results and carried out experiments that showed the interaction of the ions in solution with the electrodes was responsible for the voltage, rather than any interaction with the graphene.
If Xus graphene battery is harnessing the thermal energy of motion of the ions to generate electricity, this source of energy is essentially unlimited. The researchers say their experimental results provide a huge breakthrough in the research into self-powered technology.
More information: Self-Charged Graphene Battery Harvests Electricity from Thermal Energy of the Environment, arXiv:1203.0161v2 [cond-mat.mes-hall] http://arxiv.org/abs/1203.0161
Abstract The energy of ionic thermal motion presents universally, which is as high as 4 kJbullet kg-1bullet K-1 in aqueous solution, where thermal velocity of ions is in the order of hundreds of meters per second at room temperature1,2. Moreover, the thermal velocity of ions can be maintained by the external environment, which means it is unlimited. However, little study has been reported on converting the ionic thermal energy into electricity. Here we present a graphene device with asymmetric electrodes configuration to capture such ionic thermal energy and convert it into electricity. An output voltage around 0.35 V was generated when the device was dipped into saturated CuCl2 solution, in which this value lasted over twenty days. A positive correlation between the open-circuit voltage and the temperature, as well as the cation concentration, was observed. Furthermore, we demonstrated that this finding is of practical value by lighting a commercial light-emitting diode up with six of such graphene devices connected in series. This finding provides a new way to understand the behavior of graphene at molecular scale and represents a huge breakthrough for the research of self-powered technology. Moreover, the finding will benefit quite a few applications, such as artificial organs, clean renewable energy and portable electronics.
Schematic diagram showing the experimental setup of the device with Au-Ag electrodes. Image: arXiv:1203.0161v2
Experimental setup of six graphene devices connected with a commercial LED before (a) and after (b) it was lighted up. Image: arXiv:1203.0161v2
As usual, the device contains exotic elements/materials in some way. Why can’t “they” make a battery out of dog poop and toenail clippings?
Still, I wonder what is really going on here. The clue is why it stopped working.
Those ingredients are only useful when building a Kenyan that gets to be president....
How about potatoes instead?
It probably consumed one of the ingredients just like any other battery.
So many vital parts missing from this article. Like, what was the current draw? How many watts?
Just taking some educated guesses - a forward voltage drop of 1.5 V should be enough to turn on most LEDs and if they just dimply lit, most LEDs can light visibly with 10 milliAmps.
So, doing the math:
0.01 Amps x 24 hours/day x 25 days = 6 A-Hrs
1.5 Volts x 0.010 Amps = 150 mW
This isn’t gonna set the world on fire. I think we’d do better with potatos, unless I”m missing something glaring (and that has happened before...)
The energy that it takes to create the battery is most likely intense.
Getting energy from the “ambient thermal energy” is breaking the Second Law of Thermodynamics. That would be a huge breakthrough; bigger than cold fusion.
Some say that the 2nd law is only statistically a law, and that it can be broken on the microscopic level. Others say it is universal law. One good reason to suspect that it cannot be broken at the chemical level is that no organism has tapped in to the unlimited energy. One very scary thought is that it is possible, and that we engineer an artificial organism that does it, and that organism proceeds to turn everything into itself.
This is all very cool, and if it is true, we are doomed.
I’m holding out for dilithium crystals. Good enough for intergallactic warp speed, then plenty good for my 11 year old Ford.
I don’t think it’s breaking the 2nd Law at all.
The device, if it works as they believe, gets its energy from then movement of ions, kinetically, in the solution.
They said that the device was able to keep up the voltage for twenty days. I am assuming that they left it to sit, as vibration free as possible, for twenty days and eventually the ions settled down and quit moving, or moved so slowly as to not create enough kinetic energy to generate the necessary voltage. If this is the way the device works, we could eventually store that energy in large quantities in batteries or ultra capacitors to do really useful stuff.............
Well - there is even a song/video about it!
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