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Author: Subject: Hydrogen from [bio]glycerine by electrolysis for fuel cells
blogfast25
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[*] posted on 7-10-2013 at 05:01


Quote: Originally posted by kmno4  

Do you know any premise that such a (quantitative) electrolityc glycerin decomposition (to H2 and CO2) is practically possible ?????


No. But is that a good reason not to try and develop it?




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deltaH
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[*] posted on 7-10-2013 at 05:26


Very good news guys... I wrote to a supplier of DSA plates a couple of days pleading for help with this amateur science as this WOULD require DS anodes that goes beyond what I can afford NOR easily source.

DSA = dimentionally stable anode

I referred them both to my homepage and THIS thread!

They just wrote back and said they are happy to help and provide me with experimental electrodes!

YAY :D

They recommend the iridium oxide types as they are oxidation resistant as hell and they know from experience that they tolerate sugars and organics well.

YAY :D

Looks like I can finally start experimenting with it and report some results!

Will keep you updated when and how this develops.

Sorry I don't want to post their name until they confirm that I can.

YAY :D

[Edited on 7-10-2013 by deltaH]




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papaya
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[*] posted on 7-10-2013 at 06:19


Sh**, I have to open some 5 pages long discussion myself, how could I miss the point :P
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deltaH
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[*] posted on 7-10-2013 at 06:48


@watson.fawkes

I quote you thus from this thread:

Quote:
I've already stopped responding to you for this reason. I've got no time for someone who, when steered in the right direction, doesn't go off and do some work before asking another question.


Quote:
No you haven't. You've presented a number of theoretical calculations with not even a nod to real-world inefficiencies of actual apparatus. Hint: Go learn what the third law of thermodynamics is about.


?... sigh

@blogfast25

Thanks for the support!


[Edited on 7-10-2013 by deltaH]




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deltaH
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[*] posted on 7-10-2013 at 07:22


Quote:
deltaH, I think your idea became your obsession and leads directly to madness.
Do you know any premise that such a (quantitative) electrolityc glycerin decomposition (to H2 and CO2) is practically possible ?????


See attached paper... I'm surprised at just how recent this is!

Seems like there hasn't been great success with acidic media, but alkaline works. I might be able to improve maters as the acidic media version would be more practical.

Anyhow, as far as the current state of the art goes, I quote thus from the attached paper:

"The templated binary Pt84Ru16, Pt96Sn4 and ternary Pt88Ru6Sn6 catalysts
supported on a glassy carbon electrode enhanced the complete oxidation of glycerol to CO2 in 1.0 M
KOH [30]."

They go on to say that a palladium rhodium catalyst also produces mostly carbonates in 0.1M KOH.

Also have some efficiencies for you guys for the first time:

"For application to power generation, approximately 10
m3 day-1m-3 (reactor volume basis) of H2 was produced from glycerol over Pt on a ruthenium-iridium
(RuIr) oxide catalyst in a proton exchange membrane (PEM) electrolysis cell with an energy efficiency
of 44% [32]. Although this production rate is high compared to that obtained with microbial cells, it is
still low compared with a conventional PEM water electrolysis cell."

Not too shabby for a start...


Attachment: electrochem glycerol.pdf (445kB)
This file has been downloaded 470 times

[Edited on 7-10-2013 by deltaH]




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[*] posted on 7-10-2013 at 12:46


I'll try and read that paper tonight. But it'll need more than just a quick read...

Curb your enthusiasm deltaH, two encouraging quotes are nothing more than that.




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deltaH
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[*] posted on 7-10-2013 at 12:52


@blogfast25

Curbed. Yeah I too need a good read but happy to find a paper that seems much closer to the mark. Also need to chase up on sub references in there... but it's two breaks in a day... I am pleased with that!

[Edited on 7-10-2013 by deltaH]




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[*] posted on 7-10-2013 at 14:52


Quote: Originally posted by deltaH  


See attached paper... I'm surprised at just how recent this is!


.... produced from glycerol over Pt on a ruthenium-iridium
(RuIr) oxide catalyst in a proton exchange membrane (PEM) electrolysis cell with an energy efficiency
of 44% [32]

I see the paper. The funniest thing in it:
Some of these compounds have a significantly higher market value compared with that for crude glycerol (88 USD/kg or 111 USD/L) :o
Ref.[30] is not worth reading.
Crappy reference [32] attached.



Attachment: ooo.7z (267kB)
This file has been downloaded 205 times





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[*] posted on 7-10-2013 at 14:59


I see that kmno4 had a strong reaction to glycerol:P
jokes aside i belive that it may be hard to get a hold of those electrodes if you don't have much money at the time.




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deltaH
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[*] posted on 8-10-2013 at 00:47


@kmno4

Thanks for that... but I found the 'crappy reference[32]' not so crappy, but I suppose crappy is high praise compared to something that's 'not worth reading' :P

In fact I was very pleased to see that they conducted their electrolysis in dilute sulfuric acid... now THAT is something to write home about.

@bismuthate

Indeed... but he's helping in his own way and I am grateful for that.

About those electrodes, yeah I think I can forget about copying exactly the published electrodes with my current resources, but fortunately I have a strong background in heterogeneous catalysis, so I think can fudge something.

As I've mentioned earlier, I've also just received confirmation from the guys who are going to sponsor me a couple of IrO2 electrodes, so that's a nice base to start with.

@everybody else (general points of discussion)

I was very please to find a local manufacturer who are up to scratch with electrolytic electrodes. They specialize in PGM types... no surprise as SA produces most of the world's supply. You can check them out at nmtelectrodes.com

Hopefully I can say that, if not, mods please u2u me and I can take it off if not, but I think as they sponsored amateur science, it's the least I can do.

Anyhow, so yeah at the moment I have an excellent electrode base to start out with. I could always impregnate the IrO2 porous coating with other PGMs if required. The IrO2 would effectively become my catalyst support, though it would probably itself be at least partially catalytically active.

I can tell you that IrO2 electrodes appear to be tough as nails, so hopefully they will stand up to the abuse I'm about to unleash lol.

I do agree though with knmo4 that there doesn't seem to be any real in-depth understanding or proof of exactly how these catalysts are working, but to be fair this is not uncommon in the early days of such emerging technologies. Often the case with things like this is research group X proposes their own 'unique' version and shows how marvelously it works...

The important take home message though seems to be that this works in varying degrees with all sorts of exotic PGM concoctions which really tells me that most PGMs would work at least to some degree... that's also good news.

I think the one big thing that all this research hasn't tried, is to use another oxygen source beside for water and I think THAT could make a BIG difference.

By the way, I realised last night just before falling asleep that hydroxylamine would fail on this basis... What I mean is that even if hydroxylamine successfully forms hydroxylamine-O-sulfuric acid when mixed into a concentrated sulfuric acid electrolyte, this eliminates water there and then. BUT the hydroxylamine-O-sulfate anions migrating to the anode would not supply any additional oxygens at the anode, in fact, it would need to consume a water molecule in order to regenerate sulfuric acid again.

The only true oxygen supplier to such a proposed mechanism would be things like peroxide forming hydroxypersulfuric acid and hydroxypersulfate anions. This truly inject one oxygen atom to the overall ballance at the anode.

So... yeah, I think hydroxylamine is sounding less and less of a useful oxygen source in a strongly acidic environment... I suppose all the chemists are shouting right now that that's no wonder, it's a freak'n reducing agent! I have to admit my previous train of thought along this line was not sound... I was thinking that despite being a reducing agent, it could contribute its one oxygen atom to the carbons of glycerine, what I didn't realise is this one oxygen is effectively lost in the esterification process to sulfuric acid which I'm proposing is critical for transport of these species to the anode under strongly acidic conditions and at very high rates (it's my first hypothesis for improving on this process).

Live and learn!

[Edited on 8-10-2013 by deltaH]




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blogfast25
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[*] posted on 8-10-2013 at 02:52


Quote: Originally posted by kmno4  
Crappy reference [32] attached.



Why is it a 'crappy' reference, kmno4? I'm just reading it and the science looks OK to me, said as a non-expert in fancy electrochemistry.




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kmno4
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[*] posted on 9-10-2013 at 02:11



In this paper they claim 44% efficiency - on what basis ?
The only given measurements are CV (and its shape indicates strongly irreversible reaction) and polarisation curves.
No analytical results are given

[Edited on 9-10-2013 by kmno4]




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