Researchers create self charging "ambient" battery w/ graphene (Maxwell's demon)

Researchers at Hong Kong Polytechnic University claim to have invented a new kind of graphene-based "battery" that runs solely on ambient heat. The device is said to capture the thermal energy of ions in a solution and convert it into electricity. The results are in the process of being peer reviewed, but if confirmed, such a device might find use in a range of applications, including powering artificial organs from body heat, generating renewable energy and powering electronics.

Article

Paper



Right after the "cool diode" breakthrough I posted about earlier there's this very significant breakthrough that happened the past week. In fact I would say this is much more significant as the energy levels are many orders of magnitude bigger. Basically this is exactly what Maxwell's demon is;

Maxwell's demon wikipedia

High velocity ions collide with the graphene and produce an electron. Due to the high carrier mobility of graphene and the dissimilar electrodes this electron will zip through the graphene and generate a current/voltage if the circuit is closed. This would probably decrease the temperature of the solution but the ambient heat will reheat it and thus "recharge" it.

I suggest you also read the paper as it's very understandable and contains much more information. Especially the following piece which to me rules out any galvanic effect, that I'm sure a lot will claim it to be.

All the electrodes, graphene edges and substrates were sealed from exposing to the electrolyte solution. The exposed area was around 3 mm × 5 mm.

Also rare is that the researcher himself is commenting on the said article.

Actually, I just finished the measurement of one sample. It seems that the sample shows a peak power output when a 22kohm resistor loaded to it. The theoretical peak power density for this sample is about 70,000 w/ Kg.

It seams that so many arguements about my experimets. The updated paper and more experiments which can support the mechnism will also be updated to it. Maybe the full paper can answer all the questions. It will be ready when Arxiv.org back to work this monday. Thank you all for your suggestions. Zihan XU

I'm really excited about this, it's so simple and the implications are huge. Can't wait to see this scaled up as the exposed area in this experiment was a mere 15mm².

Sounds too good to be true. But still, it does not sound completely implausible to me. I always thought something like this should be possible. I hope this discovery can be used in actual useful applications. I will definitely do some more reading on the subject.

Maybe you cud use them in cars too.. They could charge from your car engine as it heats up...

I hope that this is not some galvanic effect.

Since electrons move through graphene at extremely high speeds (thanks to the fact that they behave like relativistic particles with no rest mass), they travel much faster in the carbon-based material than in the ionic solution. The released electron therefore naturally prefers to travel through the graphene circuit rather than through the solution. This is how the voltage is produced by the device, explains Xu.

This can not explain the voltage. Why should electrons moving in the graphene prefer a certain direction.

0.35 V was generated when the device was dipped into saturated CuCl2 solution

Copper (Cu) oxidation potential is 0.34V. Coincidence?

at 70kilowatts per kilogram this blows IC engines out of the water!!

Lets hope this is actually workable and or scaleable because if it is our energy worries are effectively over.

I'm a little skeptical here, as well.

The theory is fairly sound (although I agree that induced voltage polarity is a bit of a question, here) - but this would be an absolutely massive development. One that I was truly not expecting to see for another 50-100 years, at least.

If true (a fairly considerable if) - this sets the groundwork for making us a null-entropy society (while being pre-fusion... quite interesting). The ramifications are simply on a scale that we can't quite predict from here (much like how the development of the modem led to the internet taking society by storm decades later).

We also found that asymmetric electrodes can define the current direction in the circuit. For comparison, two devices with identical electrodes, namely Au-Au and Ag-Ag, were fabricated. In such devices, it was difficult to control the current direction. That is because the excited electrons flow across graphene surface in random directions and small vibration can cause the change of the current direction (Supplementary Fig. 11a). To interpret this, a work-function tuning mechanism was proposed (Supplementary Fig. 11b).

Given the random directions of the single electrons the total current should be zero. Replication is required I think.

If the output is efficient I see the next wave of solar cell. Also great apps for geothermal applications. Built into roof tiles Jacket phone jacks awesome!

I read the paper, and it does look promising. Didn't understand it all, but the parts I did understand made sense. I will play the devils advocate, as I too require to see this reproduced and am not convinced yet.

0.35 V was generated when the device was dipped into saturated CuCl2 solution

Copper (Cu) oxidation potential is 0.34V. Coincidence?

I don't know about the correlation between oxidation potential and temperature, but if there isn't any, then figure 2a is hard to explain with oxidation potential.

Given the random directions of the single electrons the total current should be zero. Replication is required I think.

As they already say in the quoted text, random directions of single electrons only happen with identical electrodes. With different electrodes the direction is fixed.

There was already a post about "why is there a preferable direction for the electrons?"

Well Ag and Au have different electrode potentials. But the article quoted does not clarify that.

reply to post by buddhasystem


Even so, that arrangement would seem horribly inefficient, as the voltage potentials generated across the 2d plane would largely cancel itself out (two microns away, a particle hits with an opposite angle and effectively nulls the charge across the terminals).

Even if you are getting a net voltage potential because of the different biases, the only real generation being done is within a very small area near each terminal.

reply to post by buddhasystem
As Aim64 said. The electrode potential would be canceled. Graphene is a conductor(think of Faraday cage). There would be a potential at the contact of the electrodes with graphene, but no potential in the graphene.

reply to post by moebius


Which means the device may work - they just may have a very inefficient setup (or the illustration/description is overly simplistic and neglects to mention a much more dense layering scheme).

Scaling the device down to have only a tenth of a millimeter or less between each electrode terminal and 'stacking' them in a manageable series-parallel array would be far more productive, in theory...

Though care would have to be taken to ensure proper insulation existed to stave off both chemical reactions and unwanted current flow (construction at such scales means even a few volts can become a problem).

reply to post by Aim64C
But from my understanding they describe it as a graphene surface effect. Thermal Cu ions hitting exposed surface. If there is no potential in the graphene there should be no current.

All the electrodes, graphene edges and substrates were sealed from exposing to the electrolyte solution. The exposed area was around 3 mm × 5 mm.

They also make it sound as if the collisions would introduce a measurable current in a certain random direction using identical electrodes. But there shouldn't be any current at all from random electron movement.

We also found that asymmetric electrodes can define the current direction in the circuit. For comparison, two devices with identical electrodes, namely Au-Au and Ag-Ag, were fabricated. In such devices, it was difficult to control the current direction.

reply to post by moebius


Couldn't the generated current itself cause the potential difference required for the electrons to have a preferable direction? That could explain why a disruption could cause the direction to change. It would start with an equilibrium, electrons cancel each other out. By chance one direction results in a net current and sort of a chain reaction starts, more and more electrons go into this same direction as result of this increase in net current. Just thinking out loud here. Another thing that comes to mind is that the emf somehow aligns the ions, resulting in a preferable direction. Though I don't know enough about the subject to say that this is even possible. I think the paper does not include enough information to give us the answers. And I do wonder where I can find figure 11.

reply to post by -PLB-

Electron avalance effect? en.wikipedia.org...
But it is usually driven by an external e-field and won't happen in conductors.

Maybe it has something to do with the high electrons/holes mobility in graphene? physics.aps.org...

This unusual relationship causes conduction electrons to behave as though they were massless, like photons, so that all of them travel at roughly the same speed (about 0.3 percent of the speed of light). This uniformity leads to a conductivity greater than copper.

But then physicsworld.com...

Despite all these advantages, graphene suffers from one serious flaw – the electrons and holes created in the bulk of the material normally recombine too quickly, which means no free electrons to carry current.

I guess we will have to wait for a more complete paper and/or independent confirmation.

Frome the link I posted before:

Separating electrons and holes The researchers did this by placing palladium or titanium electrodes on top of a piece of multilayered or single-layered graphene. The metal "fingers", which have different work functions, produce electric fields at the interface between the electrodes and graphene. The field effectively separates the electrons and holes, and a photocurrent is produced when light is shone onto the device.

This would be the version as described by Aim64. You have a single graphene layer and ions instead of light photons inducing a current between the electrodes.

I am speculating.

But what if the electrons from Cu collisions are fast enough to enter the contact area before recombining? Then the different electrode potentials at the contacts would enforce a current direction.

As a consequence one should be able to measure a temperature difference between the graphene and electrolyte proportional to the current. You would get a thermal analogy of the photo diode.

Now the physicists here are free to stone me to death, he he.

Love Maxwells demon! I always figured it was a matter of time before it was implemented into something useful!
Awesome find OP, thanks for bringing this to our attention!

Regardless, stuff like this makes me wish I had the resources necessary to investigate "profound-but-simple" claims, such as this. Unless I'm grossly under-estimating the engineering complexity involved, here, a hundred thousand dollars seems like more than enough to attempt to replicate this experiment.

Though a few thoughts have come to mind... such as how the graphene is joined to the electrodes... is it purely mechanical, or is there a 'weld' or 'solder' of some kind?