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Tiny particles power chemical reactions – Massachusetts Institute of Technology (news.mit.edu)
51 points by mardiyah 13 days ago | hide | past | favorite | 13 comments

This seems neat but I’m also a mere computer person and vaguely knowledgeable in electrochemistry. A few questions for anyone who knows more about this subject:

I’m wondering where the electrons being yanked out of the particles come from, and how they end up flowing back into the nanotubes particles. Do they come from the carbon? Are they somehow stored in the tube structure? Also, how exactly do the electrons end up getting pulled back into the structure if they’re yanked out in the first place. Wouldn’t the system tend towards some equilibrium, rather than what I’m intuiting as an oscillation of charge?

Also, how exactly does this give an advantage to nanomachines over a traditional battery? Do we just not know how to build them small enough, and therefore this is neat because we can (crudely worded, forgive me I’m not an expert) hook these particles up to nanomachines so they can generate power with the whole chassis suspended inside the solvent? Maybe it’s just easier to manufacture than e.g. batteries?

This seems like a cross between a standard battery and a flow battery. A standard battery has an anode, separator, and cathode connected to each other, and counter-ions (eg Li+) flow from the anode to the cathode, allowing a wire connecting the anode and cathode to generate a potential, since the counter-ions "want" to be in the cathode more than in the anode. Many standard batteries can be recharged by reversing the voltage and making the electrons flow in the opposite direction.

A flow battery uses a solvent for the anode and the cathode, which are then flowed through a tube containing a separator, across which the same voltage can be extracted. Flow batteries are recharged by taking the spent fuel out of the battery and re-oxidizing/reducing it, after which it can be reused in the flow battery.

The way I'm reading this is that its the anode (CNTs) and separator (teflon) of a flow battery, with a reducible organic solvent molecule (CH3CN) serving the purpose of the cathode. I don't see anything playing the analogous role of the counterions, but perhaps this configuration doesn't need it because the distance traveled by the electrons is atomic-scale.

So, the electrons come from the pi-shell of the CNTs, and flow into the pi-system of the CN group, where they can do some chemistry. The electrons don't flow back, since the band they flow into is lower than the band they come from (Fig 1b of the Nat Com paper). My reading of the paper is that the particles would be recharged by taking them out of the solvent and exposing them to a current.

The advantage of this system over a traditional battery is that you can provide electrons at a higher potential to nanomachines that could then use that energy to do some work, without needing to be wired up to something. I'm thinking here of a molecule that "walks" along a fiber or something, and the higher enegy electron could cause a conformational change in the molecule to move it down the fiber.

There's a nice analogy here to the way that biological systems use chemical species like NADH to fuel chemistry via redox reactions.

Just the best guess I can make at this point, please reply if I've missed something.

Correction: I meant "NADPH" instead of "NADH". It's been 25 years since I've done any biochem, and obviously my skills have rusted (haha, electrochemistry joke).

The Z-scheme in photosynthesis is exactly the type of way I could see this being used: put a high energy electron into one state, and generate a cascade of subsequent chemical reactions as the electron relaxes into a lower energy state: https://en.wikipedia.org/wiki/Photosynthesis#Z_scheme

Thanks for this reply, makes sense to me now and now I have more things to Google! Any idea how they’d extract the particles from the solvent to recharge? I’ll try reading the paper as well.

Filter paper? I'm only somewhat joking here, since I imagine the particles are micron-sized.

Here's the link to the Nat. Comm. paper since I couldn't find it in the press release: https://www.nature.com/articles/s41467-021-23038-7

I was educated and worked as an organic chemist and did some organic electrochemistry and I have no freaking clue what this is about based on the press release. The attempt at putting it in plain English appears to have completely butchered any understanding of the science.

It appears that by coating carbon nanotubes with telfon on one side (after ground into a film), they can create a potential gradient with an oxidizing solvent on one side? But so many pieces are missing - where do the electrons come from? What’s on the Teflon side of the membrane? An electron donor?

My takeaways from the Nature article:

The underlying driving enthalpy seems to be the solvent adsorption exotherm. By extension once full wetted the particles stop producing voltage, but can be dried and rewetted.

As with typical electrochemistry both an oxidation and reduction are performed simultaneously: Oxidation on the PTFE side and reduction on the CNT side. Essentially each particle is its own little electrochemical cell, deriving its working potential from the solvent-surface interaction.

Ah. Good ol' carbon nanotubes...

The only application CNTs fail -completely- at, is leaving the laboratory.

Unlike those pesky CNTs, I'll just see my way out now.

This is a valid criticism. There are several threads in science that are seemingly funded indefinitely despite modest to negligible progress and other threads that are utterly starved for funding.

Is there a bias at funding agencies that research in "carbon nanotubules" gets picked over "X research" year after year?

One long running research area that I'm reminded of is artificial photosynthesis. Let's make a combination PV cell and electrolytic cell, because optimizing both together is going to be totally easier than doing it separately. /s

From the perspective of a career minded professor sitting on a funding committee it's a good way to guarantee a growing set of citations. As long as people still research X the first papers in X will garner citations.

Oh like masers and lasers you mean ;-)

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