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chironex
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Graphene oxidation using ferrate instead of permanganate and acid
So I just found this paper and got very very excited. Since I first started working with graphene, and specifically making the oxide, I was frustrated
with how dangerous the reagents were. It made doing the reaction a lot of work that required careful observation and numerous safety measures. The
standard way to make graphene oxide is hummer method which uses a mixture of concentrate sulfuric acid, nitric acid and potassium permanganate. This
had a nasty habit of releasing clouds of toxic gas suddenly or potentially exploding. Eventually they got to tour method which subbed in phosphoric
acid for the nitric. This made things less chaotic in that it rarely fumed, but risk of explosion was still very much there. It becomes explosive
about 55C and you need to heat it to 50c for 12 hours. Not fun.
In comes this new paper I found LINK. In it they detail the use of totally different reagents. Instead of the acid and permanganate, they use potassium ferrate as the oxidizer.
If it works as well as the permanganate this would be amazing. It would make working with graphene oxide orders of magnitude easier. Potassium
ferrate is pretty harmless and there's no risk of explosion. Yet it seems to do the same job. They also claim their yield is higher at 40% vs ~30% for
hummers method. Suffice it to say I'll be testing this first chance I get in a week or two.
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AJKOER
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If you are preparing your ferrate by the thermal path (much heating), I do recall reading a paper where there is an explosion hazard presence also.
Those who have not departed with a body part in its preparation so far may be of different opinion.
So don't forget the safety gear quite yet, as you may find it unexpectedly needed.
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WGTR
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Under the right conditions, highly oxidized graphene oxide itself is somewhat explosive:
http://www.sciencedirect.com/science/article/pii/S1748013212...
There are room temperature processes out there, that don't involve heating permanganic acid just under its decomposition point:
https://www.researchgate.net/profile/Huang_Ming2/publication...
Also, there is a mild oxidative electrochemical process that uses ammonium sulfate, and is quite tame, if you don't need heavily oxidized material.
An organic solvent may be needed (NMP, DMF, ETOH/H2O, etc) for exfoliation in that case, due to fewer functional groups.
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chironex
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So to make the ferrate I'll be using a little ozone generator (rather than hypochlorite cause i'd rather not work with chlorine). Means there's a
literal off switch to the reaction, at least some what. I'm actually hoping to see if I can make a room temperature variation of the reaction to
produce graphene oxide by modifying the ferrate procedure a bit. Im not saying that ferrate is entierly safe, this is chemistry, it'd be suicide to
assume anything was entirely safe. Of course I'll take precautions, but compared to hot manganese heptoxide, I'm fairly relaxed about the whole thing.
I do actually require large amounts of oxidation as I'm using the graphene oxide as starter for fiber preparation and stuff. I'd never seen the
ammonium sulfate method though, I'll have to look into it.
For exfoliation the best (and most readily avialiable) mix I've found is acetone and di water at a particular ratio, i think like 75%/25% if memory
serves. Works ok for graphene analogs as well (hboron nitride for example, though it settles out quickly)
[Edited on 22-12-2016 by chironex]
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chironex
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Quote: Originally posted by chironex  | So to make the ferrate I'll be using a little ozone generator (rather than hypochlorite cause i'd rather not work with chlorine). Means there's a
literal off switch to the reaction, at least some what. I'm actually hoping to see if I can make a room temperature variation of the reaction to
produce graphene oxide by modifying the ferrate procedure a bit. Im not saying that ferrate is entierly safe, this is chemistry, it'd be suicide to
assume anything was entirely safe. Of course I'll take precautions, but compared to hot manganese heptoxide, I'm fairly relaxed about the whole thing.
I do actually require large amounts of oxidation as I'm using the graphene oxide as starter for fiber preparation and stuff. I'd never seen the
ammonium sulfate method though, I'll have to look into it.
For exfoliation the best (and most readily avialiable) mix I've found is acetone and di water at a particular ratio, i think like 75%/25% if memory
serves. Works ok for graphene analogs as well (hboron nitride for example, though it settles out quickly)
[Edited on 22-12-2016 by chironex] |
So I looked into the room temperature version you posted. It's the same as the tour method, they just leave it for 3 days instead of the usual couple
of hours. I guess that would work. Still means cleaning out a ton of acid though which is a massive pain. If the ferrate thing works, it's still
preferable. Electrochemical is another promising alternative, but only if the oxide is produced and not just normal graphene
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Aztral
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| Quote: Originally posted by chironex | | They also claim their yield is higher at 40% vs ~30% for hummers method. Suffice it to say I'll be testing this first chance I get in a week or two.
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Definitely interested in the results.
I "was" about to get start getting the stuff I need to produce GO via Tours, but this looks more promising. I'll start trying to source potassium
ferrate 
As to electrochemical GO...is there actually an electrochem route?
Now I do currently make "graphene" (allegedly ~80% 1-3 layers) with graphite gasket material, sodium sulfate solution and a simple matter of voltage.
But would love to know if GO is possible via electrochem
[Edited on 26-12-2016 by Aztral]
[Edited on 26-12-2016 by Aztral]
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chironex
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I saw one method that used CTAB in the electrolyte solution as well as some sort of pretreatment on the graphite foil to make electrochem GO (if
memory serves, but i read the paper like a year ago), I'll have to dig it up. So it is possible, it's just not as efficient I think. I also saw
another method that used piranha solution in the microwave, but like, why would you ever do that. (Well, it makes GO in literally a minute, so there's
that, but also piranha solution in the microwave). *cough* That said I tried it out once but was too scared to leave it on for the full minute so did
it in 10 second intervals and it didn't work. Would not suggest ever trying that. If this ferrate thing works it'll simplify all this so much
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Aztral
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Yup. I'm still looking for potassium ferrate.
I was reading the making ferrate thread here, and results seemed less than spectacular, and quite a pain.
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clearly_not_atara
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Potassium ferrate is simply highly unstable. It can explode when concentrated, but usually it decomposes while you're trying to concentrate it.
Making it yourself really seems like the best option; you just have to work with it. It's not widely used for a reason. I think that fusion of KNO3
with Fe2O3 is overlooked.
[Edited on 28-12-2016 by clearly_not_atara]
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chironex
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Ya from what I've seen it's a "make it as you need it" kinda chemical. I'm going to explore the ozone route first since it would be the easiest if it
works and should provide high purity material, but I'll also have a look at the ignition method since it's faster and also fairly easy
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clearly_not_atara
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Excuse me, I mis-posted; it's the ignition of KNO3 with Fe, not Fe2O3. Although it strikes me that Fe (II) salts could possibly be used to
attain a more controlled reaction that uses less nitrate. Ferrous carbonate comes to mind, since it is much more easily prepared (and stable) than
ferrous oxide.
4KNO3 + FeCO3 >> 4NO2 + K2CO3 + K2FeO4
[Edited on 28-12-2016 by clearly_not_atara]
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chironex
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So thanks to a convenient, though maybe unfortunate situation I got a chance to test out my ozone generator. Its nothing fancy, just a simple unit off
amazon but it works great. Used it to de-stink a bag. point is, ozone generator is working properly.
I've also been thinking about all this some more and have an idea for a modified procedure. In most of the papers they make the ferrate first, purify
it, then treat the graphene with it. However due to my work with graphene previously, it made me wonder if this was necessary. Things to note. First,
if you exfoliate graphite down to graphene, the chemical properties of the material change significantly and it's easier to modify the material.
Second, conveniently, ferrous sulfate makes a great electrolyte for electrochemically exfoliating graphite into graphene. And graphene will stay
suspended in a ferrous sulfate solution for a fairly reasonable amount of time. The ferrous sulfate doesn't make it crash out of solution like some
other salts.
SO with that all said my thoughts on the experimental setup is as follows. Fill a beaker with ferrous sulfate solution and a gram or two of graphite.
Place it in a sonicator and run it for an hour to partially exfoliate the graphite. Insert the air stone/ozone output hose into the solution (might
replace this with a simple glass pippette or tube so the ferrate doesn't eat the hose). At this point, turn on the ozone supply. This should generate
the ferrate in situ, rather than trying to purify it later. And as an added bonus, you've got the ozone acting as a secondary oxidizer. It'll also
produce some iron hydroxides but they'll continually be converted to ferrate by the ozone. In this setup, between the ozone and the ferrate, it should
be more than enough to oxidize the graphene as it's being exfoliated. In this way, it'd be very similair to the ozone/uv procedure, but all chemical.
Thoughts?
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Boffis
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I don't think you will generate ferrate in situ by this method since the generation of ferrate requires strongly alkaline condition so you would need
to use say NaOH or KOH but this would precipitate the iron as ferric hydroxide. This may not be a problem particularly if you use a split cell since
you may be able to generate ferrate in this way but I don't know how this would effect the graphene/GO production.
Incidently I once considered trying to make potassium mellilate by electrolysis of either nitric acid or alkaline potassium permanganate in a split
cell with graphite electrodes. I built the rig but in the event I never tried it. This idea was based on the fact that I had previously observed that
using graphite electrodes to electrolyse certain chemical solutions resulted in the rapid disintegration of one electrode with the formation of a
brown suspension.
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chironex
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From all the literature I've seen, the precipitation of the hydroxide always happens first anyway, and is then converted to ferrate. So that shouldn't
be a problem. Though thanks for pointing out the lack of hydroxide in the procedure, i'd forgotten about that. Normally alkaline conditions will cause
GO to agglomerate, but if it's being treated with ultrasound the whole time, that shouldn't really be a problem. Also i've seen some people claiming
to retain stable dispersions even in 6% sodium hydroxide solution. I still think it'll be worth a shot. I feel the first test will be to see if
ferrate forms at all under the conditions, without the graphite. Then repeat with graphite and see if GO is produced.
Hmm, electrolysis in permanganate actually sounds fairly reasonable. I'll have to look into that. Also makes me wonder if permanganate/ozone could
work in place of the ferrate/ozone.
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Aztral
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I did try a microwave GO production method today.
1.0:2.5:0.07 HNO3:H2SO4:H2O + graphite then nuked @300watts for 30s. Can't say it was a particularly pleasant experience due to some noxious fumes,
but me and my microwave survived - yippie 
I have the results in significantly more diluted water, pending more dilution, filtering and cleaning HCL, and finally sonic dispersion in water. The
product this created does seem pretty easy to clean imho.
Not having access to more extensive testing gear, I'm not entirely sure I made GO. I can only trust that the method in the paper did actually make GO,
and hope I followed it correctly enough.
The ultimate test I'll be performing will just be seeing if this stuff "acts" like GO. Disperses in water, reduces with heat/light and makes a good
active material in a supercapacitor.
My heater/mag stirrer should be here soon, then I'll try the no-heat, 3 day stirring Tour method too
http://garf.rutgers.edu/sites/garf.rutgers.edu/files/2013pubs/nn403429v.pdf
[Edited on 6-1-2017 by Aztral]
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gatosgr
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There is another method with concentrated sulfuric acid and sodium persulfate which is the fastest chemical method, leave graphite some hours in the
h2so4,na2s2o8 solution, then wash it with aceton and then with water if you are interested in the details I can look it up later but I think the
graphite isnt very oxidized maybe you can oxidize it afterwards , electrochemical methods work too, look up robert murray smith on youtube or download
a paper on graphite electrolysis, what are you making with GO airplanes? What resin do you use and with what fiber mats?
GO will reduce many inorganic compounds easily, I guess that if you use a metal salt and heat some GO with it the solution will change color due to
the different color of the salt, this way you can test if it's GO or just brown gunk.
I dont like the methods where you work with conc. acids and toxic fumes, if you find another way tell me.
Another fast chemical method is with CrO3 but it's nasty stuff, usually these require an co-intercalants.
[Edited on 12-1-2017 by gatosgr]
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Aztral
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Thankz Gatosgr...good info.
No intention of derailing Chironex's thread and I fully-intend to get around to trying to make GO via ferrate method as well, but I would like report
the results of making microwave GO via nitronium ions.
First, I did whip the "GO" (ME-LOGr) I made this way into a supercapacitor - if you can call it that, because it was garbage and the voltage dropped
like a rock. For comparison I made another supercap from GO I bought on ebay (with all else being equal) and the voltage dropped ~10x slower. (note:
I'm working on my supercap building and performance measuring skills, so this is worth at least one more shot to rule out operator error). 
I had high hopes too because this stuff took all of 30s microwave time to make and was really conductive as stated in the paper (~2k ohms*cm-1). I
could easily coat glass and make it conductive, but it think and opaque. I'll take one more shot with this microwave GO (using the original paper as
reference), but I'm pretty much underwhelmed with ME-LOGr at this point.
And I had to wash this ME-LOGr stuff a zillion times. I kept getting this silvery, oily residue floating to the top that just would not go away no
matter how many times I washed the product. I thought it could be the sulfuric acid, but this looked more like mercury...except it floated. Maybe I
technically didn't have to keep washing it, but that silvery stuff seemed like a contaminent /shrug
But this could be the weekend I finally try the Tour method. My heater/stirrer finally came in and looks like all I have to do now is make some
deionized water ice. I'll try a smaller batch than RMS on youtube just to hopefully mitigate the size of any potential fireball, but if you don't hear
from me in a week - send in the Marines because I'm writhing in searing pain on my garage floor - lol.
Anyway, as for "other" GO methods, I'd be interested in hearing about all of them. I do know the Tour can be also done over a week with no heating or
stirring, 3 days with just stirring, or 3 hours with heating and stirring. And then there's ME-LOGr, and the ferrate methods.
Of coarse any details on tests to determine if its actually GO, or brown junk would be awesome. (I have ZnCl on hand-would that work?)
Also looking forward from Chironex on ferrate GO
[Edited on 14-1-2017 by Aztral]
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gatosgr
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You need a salt that changes color with oxidation states in acidic solution but the only way to be sure is with spectroscopy.
https://www.researchgate.net/post/How_can_I_confirm_that_the...
That silver oily thing you say is probably few layer graphene.
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Aztral
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Sweet...thank you!
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gatosgr
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People still use the flotation method to study graphene, where they make graphene float to the top of a solution and then they dip their plates to
coat them, it's called dip coating.
https://www.google.gr/search?site=&source=hp&q=dip+c...
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chironex
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My graphite finally arrived. If I can get the ferrous sulfate today, I should be able to try this finally over the next few days. One bit of weirdness
I found, according to some ltierature, a wash in alkali removes some oxidized (non graphene oxide) material from the graphene oxide which makes it
slightly less soluable. Though if the reaction is being done in alkali, this should be benificial. It would remove the non graphene oxide stuff and
allow more graphene to be in contact with the oxidizer and get oxidized. We'll see how it goes I guess.
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gatosgr
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The easiest method to make functionalized graphene is with a ball mill. What reaction will you follow to make the ferrous sulfate or are you trying
another method?
The K2FeO4 is similar to CrO3 which is used in a similar method to make graphene oxide, look it up.
[Edited on 27-1-2017 by gatosgr]
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chironex
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Ferrous sulfate I can just buy. I've never seen functionalizing graphene in a ball mill, could you send a source for that? I've functionalized
graphene hydrothermally and that was pretty neat and weird. Really need a better lab to analyze the product though.... Weird ass green crystals don't
really tell me much about the chemical structure.
Potassium ferrate was exactly what this thread was about. I read a few papers on it and it seems extremely promising, hence the thread. That said,
while it seemed promising, not many people working with graphene use it, so I'm hoping to test it out and see how easy it is. I'm also hoping to
generate ferrate in situ, rather than making it separately and adding it in.
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gatosgr
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the paper is called "Functionalized graphene nanoplatelets from ball milling for energy applications"
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chironex
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Huh. that's super cool actually. I'm gonna have to try that. The one thing is that it only seems to work on the edge of the material, rather than
throughout, but still, it's better than nothing and seems quite promising. I wonder if it could also work during sonication since similar processes
should be going on as the graphene break. I did notice a bit of weirdness when sonication in tannic acid solution, but I'll have to investigate
further and read up more.
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