Basic Electrolysis

[Farrah Day]

To date, electrolysers - though quite effective at dissociating the water molecule into its constituent parts of Oxygen and Hydrogen - are considered to be inefficient and power hungry. The very fact that the gas evolved at the electrodes is directly proportional to the current passing through the cell sees to this.

But what do most people actually understand of even basic electrolysis, how well is it really understood?

From my experiences, it seems that the regular Science Forums don’t like to talk about anything other than what they can already explain, and I’ve had threads completely removed from these forums simply because they did not fit in with the mainstream science. Quite absurd.

One thread I had removed from the Advanced Physics Forum, simply asked, quote: ‘Exactly how does electrolysis work?’

When a boff came back with, ‘you simply pass a current through water to break it down’, I knew it was going to be downhill from there. To cut a long story short, no one could give me a satisfactory answer to this apparently very simple question. They simply did not know how electrolysis actually works other than what they we’re taught at school. My thread then rather conveniently got mislaid - so much for the Advanced Physicists.

Let me ask you this. Why does adding an electrolyte to water in an electrolyser result in greater gas output?

The Advanced Physicists will tell you that the electrolyte introduces more current carriers into the solution thereby allowing more current to flow, producing more gas… simples!

But, why is this? Given that those introduced current carriers do not actually interact at the electrodes; they do not themselves take up or drop charges at the electrodes, so what is that all about?

I think we tend to take far too much for granted. Things are not always as clear cut as they may at first seem.

[EgmQC]

To date, electrolysers - though quite effective at dissociating the water molecule into its constituent parts of Oxygen and Hydrogen - are considered to be inefficient and power hungry. The very fact that the gas evolved at the electrodes is directly proportional to the current passing through the cell sees to this.

But what do most people actually understand of even basic electrolysis, how well is it really understood?

From my experiences, it seems that the regular Science Forums don’t like to talk about anything other than what they can already explain, and I’ve had threads completely removed from these forums simply because they did not fit in with the mainstream science. Quite absurd.

One thread I had removed from the Advanced Physics Forum, simply asked, quote: ‘Exactly how does electrolysis work?’

When a boff came back with, ‘you simply pass a current through water to break it down’, I knew it was going to be downhill from there. To cut a long story short, no one could give me a satisfactory answer to this apparently very simple question. They simply did not know how electrolysis actually works other than what they we’re taught at school. My thread then rather conveniently got mislaid - so much for the Advanced Physicists.

Let me ask you this. Why does adding an electrolyte to water in an electrolyser result in greater gas output?

The Advanced Physicists will tell you that the electrolyte introduces more current carriers into the solution thereby allowing more current to flow, producing more gas… simples!

But, why is this? Given that those introduced current carriers do not actually interact at the electrodes; they do not themselves take up or drop charges at the electrodes, so what is that all about?

I think we tend to take far too much for granted. Things are not always as clear cut as they may at first seem.

You should take a look at this 2 link, its not mysterious at all.
Faraday's laws of electrolysis - Wikipedia, the free encyclopedia
Electrolysis - Wikipedia, the free encyclopedia

Best Regards,
EgmQC

[Farrah Day]

Hi Eg, I do actually understand Faraday's Laws.

But, like the guys on the Advanced Physics Forums, I think you've completely missed my point.

The links you provided simply give the accepted secondary school version of the process and Faraday's Laws.

The problems arise when you start looking a little deeper than that.

Where does it tell me what part an electrolyte really plays?

Or if you simply accept that it introduces more current carriers, how exactly does this cause more gas to be evolved at the electrodes when these current carriers themselves do not react?

Just little things that are never discussed or conveniently overlooked, but important nevertheless if you want to gain a full understanding of the process of electrolysis.

Farrah

[EgmQC]

Hi Eg, I do actually understand Faraday's Laws.

But, like the guys on the Advanced Physics Forums, I think you've completely missed my point.

The links you provided simply give the accepted secondary school version of the process and Faraday's Laws.

The problems arise when you start looking a little deeper than that.

Where does it tell me what part an electrolyte really plays?

Or if you simply accept that it introduces more current carriers, how exactly does this cause more gas to be evolved at the electrodes when these current carriers themselves do not react?

Just little things that are never discussed or conveniently overlooked, but important nevertheless if you want to gain a full understanding of the process of electrolysis.

Farrah

You don't seem to really understand what is talked about in the 2 link i gave you. Electrolysis, first, is a charge transfer process , you move ion. If you look on that result: 2 H2O(l) → 2 H2(g) + O2(g) you clearly see the charge added to the Oxygen, the amount of energy needed depend on the energy layer you try to influence, so different electrolyte will give different value. The energy amount needed depend directly on what you use, its mathematical and not a guesswork but im not a Chemist so i cant give you all the chain reaction equation. There alot of way to operate a charge transfer, it doesnt always imply using current, If you mix Sodium bicarbonate with vinegar, you operate a charge transfere and the end result can be mathematicly derivate and the ammont of energy used/dissipate. Its the same exact thing , but on this one you think "Its a normal reaction" but its the same point of view as Electrolysis, just a different starting process.

Best Regards,
EgmQC

[HairBear]

Or if you simply accept that it introduces more current carriers, how exactly does this cause more gas to be evolved at the electrodes when these current carriers themselves do not react?
Farrah

How could anyone say for sure without actually seeing the reactions take place? How do we even know for sure that an atom is really made of particles and not something entirely different than the typical Bohr model? I'm assuming all who post here are using the Bohr model.

Now my question is what exactly do we have in the water for electrolyte? Are we calculating for other impurities other than the electrolyte? We have to start from somewhere and pure water would be a good place if any. Don't you think?

We know from experiments that the purer the water the more resistive or insulated the medium is. If we add an electrolyte such as baking soda, how does the salt interact with water? Hydration? Is the salt an ion before it is mixed with water? Is the salt an ion always in the water or only at certain conditions in random order? How does an ion carry a charge? Can other non ionic particles act as charge carriers?

But, the big first question Farrah. Why electrolysis? We both know from hundreds if not thousands of experiments between the two of us, we see that electrolysis is pretty much what Faraday documented. Do you feel there is a way to do electrolysis that's much better than the norm, or is the better option just to look at other possibilities all together? If you know it's a dead horse, why do an autopsy?

[sucahyo]

Or if you simply accept that it introduces more current carriers, how exactly does this cause more gas to be evolved at the electrodes when these current carriers themselves do not react?

How about amp per square inch theory? there is many paper explain this.

More amp per square inch of electrode will reduce efficiency logarithmically but produce more gas because each square inch of electrode surface now have more energy (voltage*amp).

Water need energy to dissasociate into H and O. Flowing more current will increase gas production because there is now more energy. While most chemical book mention the energy needed in joule, it can also be expressed in watt, as in V * I. More watt = more water being dissassociate.

The voltage play into the heating process where voltage higher than 1.24V will produce more heat and less efficient electrolysis.

From these two point, more efficient electrolysis can be obtained with very large "active" surface with voltage between electrode maybe around 2V and low amp per square inch. The problem with this is how to blow the hydrogen/oxygen bubble that stick in the electrode surface away. sticking bubble reduce surface area that will reduce efficiency.

[Farrah Day]

Hairbear

I'm still playing with various ideas and techniques in electrolysis... still looking for something that has been overlooked - or perhaps has not been considered. I don't see it as flogging a dead horse because I'm often changing my perspective of things in order to come at it from a different angle and, I'm always learning.

You well know my feelings about Meyer's Technical Brief and my thoughts about the psuedoscience therein, but I'm not opposed to the idea itself.

It's just that it makes good sense to try to understand what is occurring at atomic level in order to see a way forward.

And, to the best of my knowledge no one has yet unequivocally managed to dissociate water with voltage alone. Yet this minor point does not seem to put any doubt in the mind of those who believe wholeheartedly in Meyer.

I don't have any problem with ionic current flow or charge exchanges nor do I dispute the fact that some compounds dissolve in water and that some dissociate into ionic species.

I myself use anhydrous sodium sulpate as an electrolyte as it's safer to have about when kids are around.

When added to water, this compound nearly completely dissociates into ions of Na+ and SO4-2.

These charge carriers obviously greatly enhance the current flow through the solution, but as they do not react at the electrodes, why is it that they do not simply end up polarising each respective electrode and stopping the process of electrolysis altogether?

Adding an electrolyte to water might well increase the level of gas output, but it also reduces overall efficiency of the process in terms of gas out/power dissipated.

sucahyo

Water need energy to dissasociate into H and O. Flowing more current will increase gas production because there is now more energy. While most chemical book mention the energy needed in joule, it can also be expressed in watt, as in V * I. More watt = more water being dissassociate.

How exactly does this additional energy create more gas output? What is the reaction process?

Afterall, I can add energy by simply heating the water by a few degrees but it won't dissociate into hydrogen and oxygen.

From these two point, more efficient electrolysis can be obtained with very large "active" surface with voltage between electrode maybe around 2V and low amp per square inch. The problem with this is how to blow the hydrogen/oxygen bubble that stick in the electrode surface away. sticking bubble reduce surface area that will reduce efficiency

It's funny, but it is often mentioned about the gas bubbles reducing the surface area of the electrodes and so reducing electrolyser efficiency, but no one ever considers the electrolyte ions doing the same.

[EgmQC]

Look how Electrolysis is calculated:

Electrolysis
Electroylsis of water and aqueous solutions
Electrochemistry, electrolysis products, simple cells, electrode equations, electrolyte, cathode, anode

i really don't understand why you didn't do simple search about Electrolysis equation before.

Best Regards,
EgmQC

[Farrah Day]

Thanks for you input Egm

But it seems we are both on completely different wavelengths here and are talking cross-purposes.

I'm not entirely sure why you keep providing these links as they don't really answer my questions. I don't have a problem with cell potentials and half-reactions per se, that's not my issue.

I'll try again.

Water with anhydrous sodium sulphate as the electrolyte in an electrolyser.

We apply, say 3 volts, and we get H2 and O2 evolved at their respective electrodes. But, why doesn't all the Na+ attracted to the cathode and likewise all the SO4-- at the anode, polarise the electrodes, creating a barrier that halts the process?

Your own words... please not another link!

Regards, Farrah

[EgmQC]

Thanks for you input Egm

But it seems we are both on completely different wavelengths here and are talking cross-purposes.

I'm not entirely sure why you keep providing these links as they don't really answer my questions. I don't have a problem with cell potentials and half-reactions per se, that's not my issue.

I'll try again.

Water with anhydrous sodium sulphate as the electrolyte in an electrolyser.

We apply, say 3 volts, and we get H2 and O2 evolved at their respective electrodes. But, why doesn't all the Na+ attracted to the cathode and likewise all the SO4-- at the anode, polarise the electrodes, creating a barrier that halts the process?

Your own words... please not another link!

Regards, Farrah

Like i said before im not a Chemist, but i think i can answer your question. At molecular level there polarization like you saw in the last 3 link i posted but what you need to know is its not all the molecule who will act the same because they are not all polarized the same way , a molecule is a combination and not a unique thing, so since polyatomic ion play a role here there a charge imbalance here and a oxidation state in your reaction but its not a fission process , you don't play at the nuclear level , you only move Charge to make the electrolysis process so not all the molecule of the Electrolyte will go to the Anode and the Cathode because of the oxidation state of the molecule, you don't affect the Carbon in the electrolyte for example so why it should go to the Anode or Cathode and stop the process ? its the current who keep the reaction alive, not what is in there.

What you said will be true in a chemical process with 2 reactant , the chemical reaction will stop when all charge is balanced, like the example i gave you with the Sodium bicarbonate and vinegar.In Electrolysis you keep pushing current and its not the entire Electrolyte who react by coating the Anode and the Cathode and stop the process.

If you want a detailed answer you should contact a Chemist who will be 100000 time better than me to explain you the reaction, im not a chemist and i can make error so i don't really want to go really far in it, talk to a chemist.

[HairBear]

Fair enough, I do understand your view of Meyer and I will refrain from using him as a source of info from now on. I can also understand your point of finding an explanation in standard terms that all can agree on.

Exactly what is it you don't understand? How to disassociate water with with voltage alone? When you have an abundance of free electrons in the medium, voltage alone will accelerate these particles to collide with molecules in it's trajectory. Disassociation by collision.

[Farrah Day]

Exactly what is it you don't understand? How to disassociate water with with voltage alone?

Hi HB.

This is where the confusion seems to lie. By dissociate water with voltage alone, what exactly are you referring to: The formation of ionic species within the water or the actual evolution of hydrogen and oxygen?

Because I'm fully open to the former occurring, but cannot fathom how the latter can occur.

It's not my lack of understanding that is the issue here it's the total lack of explanation from those who think that you can decompose water into the gases H2 and O2 with voltage potential alone.

When you have an abundance of free electrons in the medium, voltage alone will accelerate these particles to collide with molecules in it's trajectory. Disassociation by collision.

There are no free electrons in liquids. Charge carriers are an ionic species. And again dissociation by collision only provides ions... not H2 and O2! During collision the O-H bond can break, but this does not break conveniently into 2H and O, it breaks into H+ and OH-. Ions yes... but gas... emphatically, No!

Like I said in my first post too many things are simply taken for granted with little or no thought going into exactly how the processes are proceeding, what might or might not be happenning, what can and can't happen... and why!

Once you scratch through the surface and delve a little deeper, things aren't as clear cut as most people think they are... or as self-evident as many people are happy to make out they are.

Farrah

[Farrah Day]

A problem that arises when you start to dig, is the apparently universal difficulty in getting answers to questions not regularly asked. The information is just not that readily available so it’s difficult to know whether this is because, it’s simply not common knowledge or it’s scientifically unknown or contentious.

One area of contention between scientists would seem to be whether or not water is ionising throughout the liquid medium, or just at the electrodes… or doing both to lesser or greater extents.

Then there’s the addition of the ionic compound to form an electrolyte. What really does this do?

According to one camp of thought, if we electrolyse water without an electrolyte additive, the gas evolved at the electrodes is limited, not by the fact that there are so few ions in water, but rather by the fact that once the water molecule ionises at the electrodes, the unreacted, remaining ion then acts to prevent further interaction.

For example:

At the cathode, the water molecule ionises into H+ and OH-.

The H+ takes up an electron from the cathode and consequently pairs with another of the same to evolve as H2.

However, the remaining OH- ion then acts to negatively polarise the area around the cathode inhibiting further interaction between the water molecule and the cathode… at least this is how it is put forward. And apparently the whole process of electrolysis is restricted by the remaining anions basically surrounding the cathode. The same thing will of course be happening at the anode.

So what then happens when we dope the water with sodium sulphate? Well according to the same camp of thought, the positive sodium ions rush toward the cathode and diffuse all the OH- ions, while the SO4—does the same at the anode. This then allows the water molecule access to the electrodes

This is what this camp of thought says is happening and what purpose an electrolyte serves.

I just can’t buy this. What do you think?

The other camp of thought leans toward water naturally ionising throughout the liquid medium with the resulting ions simply being drawn to their respective electrodes. With only a tiny proportion of water self-ionising, the result is only a tiny ionic current flow… and consequently only a tiny amount of gas evolving.

What happens in this scenario when we now add an electrolyte?

Well the Na+ makes a b-line for the cathode, while the SO4-- heads off in search of the anode. And on the way they interact with water molecules by collision and proximity, inducing further ionisation of the water molecule.

In this scenario the electrolyte ions induce further ionisation of the water molecule by their very movement and do not simply serve to dilute the non-reactive ions left over at their respective electrodes.

For me, one problem with the first scenario is this: Why would the OH- ion resulting at the cathode hang about – surely it would be instantly repelled from the cathode, while of course at the same time being attracted to the anode.

So why would there be an issue with these ions disrupting further interaction by enveloping the cathode as suggested? The same of course applies at the anode.

Food for thought!

[sucahyo]

I myself use anhydrous sodium sulpate as an electrolyte as it's safer to have about when kids are around.

When added to water, this compound nearly completely dissociates into ions of Na+ and SO4-2.

From what I recall, most chemical will turn into NaOH or KOH plus additional polutant after a while. It is better to use NaOH or KOH, which depend on what kind of plastic that being used.

How exactly does this additional energy create more gas output? What is the reaction process?

Afterall, I can add energy by simply heating the water by a few degrees but it won't dissociate into hydrogen and oxygen.

You need to get past the minimum requirement first. Once you get past it, additional energy will crack the molecule more/faster. Increasing temperature do increase gas production.

GEET reactor do not have explicit electrode, but it can also crack water, not as H2 and O2 though:

4) Gas analysis

We have done a real-time gas analysis of H2 and O2 of the reactor out-gas (called GEET gas) But we have not found a significant content of hydrogen. Then, for us, reaction does not product hydrogen, but our measures were not very reliable (all measures on hydrogen are very difficult). But if it really is not hydrogen, the GEET gas is certainly a high hydrogenous gas (smell of ether) which got the energectic advantages of hydrogen.

I have done little arithmetics on a GEET modifed Diesel tractor and the results give that GEET gas (obtained from just water and air) supplies more energy than the hydrogen extracted from the same quantity of water (if GEET gas was just hydrogen)!! However, the leak of measuring ways has given very aproximate results, but the fuel consumption of this modified tractor was, all the same,divided by 2. Here are the detailed arithmetics (but in French).

It's funny, but it is often mentioned about the gas bubbles reducing the surface area of the electrodes and so reducing electrolyser efficiency, but no one ever considers the electrolyte ions doing the same.

If ion still in liquid state, it still conduct. When it is in gas it reduce conductivity and become electrical isolator. Bubble is gas and thus reduce conductivity which reduce efficiency if it cover the electrode surface because it block current.

We apply, say 3 volts, and we get H2 and O2 evolved at their respective electrodes. But, why doesn't all the Na+ attracted to the cathode and likewise all the SO4-- at the anode, polarise the electrodes, creating a barrier that halts the process?

NaOH is a catalyst, while it also part of the reaction between the water and the electrode, they don't get consumed. Just like platinum. Maybe because the Na like O and H better than the electrode.

[HairBear]

Why do we assume OH- is part of the result of the reaction? What are the properties of OH-? Maybe you could look at it in a different angle and compare the process to "Coronal Discharge" ionization of air. How does an Ozone generator generate O3 with just a voltage potential? You can make quite a bit of Ozone with only 5 watts of power.