Plasma electrolysis at lower voltages

This is a continuation of a different thread which started with the transcription of Renzo Mondaini's plasma electrolysis experiments and ended up with partial replication on my part (mainly using a cheap low-power high-voltage power supply) as well as doing related experimental research.

The main problem so far has been finding a suitable power supply for experiments at higher currents. It is not easy to find affordable regulated power supplies for these experiments, and high voltages always pose some risks.

Recently I realized however that by using considerably higher electrolyte concentrations than usual (about 15–20% KOH by weight), cathodic plasma electrolysis can start from as low as 40V, with breakdown voltage (the voltage above which current starts decreasing with voltage, signaling the transition from normal electrolysis to plasma electrolysis) around 18–20V. This means that in principle it's possible to use commonly available 0–60V / 5A adjustable bench power supplies for these experiments, at least up to moderate power.

I only have a 31V bench supply at disposal, but due to the floating outputs it is easy to use it in series with another fixed-voltage source. I happened to have a 19V / 4.5A power supply, so I am able to test the 0–50V range up to 4.5A. Below (solid region) is the current-voltage relationship of the cathodic reaction using a 1 mm-thick sharp tungsten electrode. It appears that current reached a minimum at about 45V in this test, and should only increase after that. This minimum is technically called mid-point voltage in related literature.

The non-linear results are similar in general behavior to those reported by others, for example as seen in these graphs below from https://link.springer.com/article/10.1007/s11090-017-9804-z (open access) and https://doi.org/10.1088/0963-0252/26/1/015005 (paywalled), respectively. At least up to 50V the current value reported by my bench power supply appeared to be in agreement with that of a 40A clamp meter, for what it's worth.

Here is a test with the same tungsten cathode, switching between 19V and 50V repeatedly. Gas production seems much greater at 19V where normal electrolysis should be taking place.

An interesting observation with this relatively high-current, low-voltage plasma electrolysis is that by using a tungsten rod at the anode, oxidation and removal of the oxide layer formed by the plasma is so fast that the electrode becomes cleaned up and turns quite sharp in the process. This could be a useful method for obtaining tungsten needles. Other materials tested (so far only nickel, titanium, kanthal A-1) did not seem to behave in the same way during anodic oxidation.

As far as reaction products go, I haven't been able to detect anything unusual using a CMOS "cosmic ray detector" that has been collecting background data for weeks. At the maximum voltage I can use at the moment, electrode wear is rather limited and the reaction can go on almost indefinitely if it wasn't for electrolyte evaporation, and electromagnetic noise from prior testing appears to occur when wear starts getting severe, thus at higher voltages than the mid-point voltage.

The cathode reaction however appears to be subjectively putting proportionally more heat than normal electrolysis does at a much higher input power into the electrolyte, although to be fair I only have a single temperature sensor, so this is far from a reliable indication of excess heat (example: electrolyte temperature during plasma electrolysis of 75 °C, whereas with regular electrolysis it's about 81 °C, but with more than 3 times the total input power. Odd). The plasma reaction also appears to aerosolize large amounts of electrolyte, so this would have to be taken into account when performing evaporation calorimetry.

So is this method better than using high voltage power supplies and standard electrolyte concentrations? On one hand it does allow using more affordable and safer power supplies, but on the other a highly conductive electrolyte is needed and there aren't many other choices available besides KOH and NaOH, which are dangerous to use at high concentrations. K2CO3 could be used, but the maximum conductance (at 34 wt.%) is less than half that of KOH, according to a document I found here:

https://www.emerson.com/docume…ls-rosemount-en-68896.pdf

Quote from DnG

its always interesting when types of fermentations occur and then test the sedimentation from all the tests after all of it dries out .

I have no clue about what fermentation means in this context, but since I used a couple steel bars as the counter-electrode (anode here), there is likely going to be relatively large amounts of iron in the sedimentation, as well as likely silicon from the glass jar which is being slowly etched by the relatively concentrated hydroxide solution. Better controlled conditions would be needed for checking out if there's anything interesting there.

Quote from Curbina

can , as I understand it, you will always get better results at any voltage increasing the conductivity of the solution.

That's a safe assumption, but oddly in the many papers I've skimmed on the process, most researchers use moderately low electrolyte conductivity and higher voltages. I have never read about the process taking place at voltages in the order of 40V or so by substantially increasing conductivity, which seemed significant enough to start a new thread about since there might possibly be further margins for improvement.

Quote from Curbina

[...] From that paper is this graph, of course at higher voltage the effect of electrolyte concentration is more marked, but in all cases the more salt the better.

In my case however gas production appears to almost completely stop if I switch between 19V (normal electrolysis) and 50V (glow plasma). Current is much higher at 19V, but I don't have the means to verify if the gas produced per mole of electrons passed is different at 50V. Sometimes it has been reported that gas production in plasma electrolysis can exceed Faraday efficiency, but also that such behavior is anti-correlated with excess heat (is the extra gas recombining or disappearing somewhere?).

For instance, from Mizuno et al.: https://www.lenr-canr.org/acrobat/MizunoTgeneration.pdf

Quote

Figure 18 apparently shows the tendency of excess hydrogen generation to correlate with negative heat (an

endothermic reaction). The total endothermic heat was calculated at 6540J during plasma electrolysis.

Quote

When there is no excess heat, apparently the points for the excess hydrogen distribute around the no excess

heat region as in Fig. 19, indicating the difference between heat out and electric power is zero.

Quote from Wyttenbach

You can also look at early Mills work: "R. L. Mills and S. Kneizys "Fusion Technol. Vol. 20" you have to dig it!

It's here: https://doi.org/10.13182/FST91-A29644

but they use aqueous solutions up to 0.57M concentration and voltages in the order of 3V.

34 wt.% K2CO3 should correspond to 2.46M concentration.

What should I look for in this paper, more precisely?

Quote from Curbina

If you recall, In that paper I shared a while ago (the one that you found out had plagiarized a schematic from Mizuno), they specifically tried very high concentrations (thinking on the possibility of recycling the always controversial Reverse Osmosis reject stream as electrolyte, solving two problems at the same pass, by using a waste as source of hydrogen without having to spend any resource in adding the electrolyte), and also used microwave to generate plasma, and they reported efficiency over 100% at a certain combinations of high salt concentration and plasma energy input. They were surprised and invoked the possibility of LENR as the explanation for the "over 100%" energetic efficiency.

It could be only loosely related, but in an abandoned patent application by Ohmasa, a device is described where strongly alkaline solutions of NaOH or KOH (15–25 wt.%) are employed in electrolysis under vibration stirring. A full electrolytic glow plasma is unlikely to take place, but since a requirement for it is the formation of a gas or vapor sheath around the active electrode—which intense stirring could favor—it could transiently happen even at relatively low voltages, if the electrolyte solution is conductive enough.

I have sometimes thought that ultrasonic agitation could make plasma electrolysis easier to start, but I haven't had the occasion to test/verify this yet.

https://patents.google.com/patent/WO2010023997A1/en

Earlier on, I tried replacing the electrolyte with K2CO3 at maximum conductance concentration (34 wt.%). It did not work as well as with KOH; a video of that is here. So, I replaced it with KOH also at maximum conductance (about 25 wt.%) and surprisingly it appeared to behave similarly to K2CO3 (although better in some respects: electrolysis started at a slightly lower voltage), and not quite like the previously used electrolyte solution.

Then, I recalled that with the old electrolyte solution I dissolved at least 1 cm of 1mm tungsten electrode with anodic oxidation (the process which made it sharp as shown in the opening post), as well as putting various organics into it. It also contained some iron oxides from the counter-electrode. I tried to put these impurities back. The organics didn't seem to help much right away. Iron oxide in the form of a few milligrams of Fe2O3 powder helped somewhat and turned the solution reddish as it was before, but apparently dissolving tungsten material into it did the job. It is now apparently working just like before, perhaps somewhat slightly better due to higher conductance.

Determining precisely what is exactly needed will not be straightforward, I fear. Apparently, some impurities or suspended particles make the electrolytic glow plasma reaction easier to start (or brighter) at lower voltages. This could also be something specific to the voltage-current level I'm using at the moment.

EDIT: probably this conclusion was not correct. It's likely that the KOH solution I previously used was more concentrated than I thought, since I did not keep track of how much KOH added. As I found out later, the reaction appears to improve with increasing KOH concentration up to very high levels.

Unfortunately I have little idea of what you mean exactly, but after a few more tests I think I can confirm that after evaluating the effect of temperature (the plasma reaction works better at higher temperatures) and other impurities, KOH (potassium hydroxide) does appear to consistently work better than K2CO3 (potassium carbonate) after all.

As for the impurities, I guess one can speculate that similarly with ordinary plasma reactions in vacuum tubes, specific mixtures may give better results than single elements/compounds in isolation, but this will be difficult to control precisely under electrolytic conditions with so many variables affecting the results.

Mark U

A lot of gas was being generated in a small area at the low voltage level; I'm not sure. Here is a brief slow-motion gif I made yesterday from that which I forgot to upload here, showing both the gas bubbles (briefly) and the plasma.

On a related note, I tried using new 25 wt.% KOH solution without other additives and it is still not behaving like it did previously even after bring temperature above 80 °C. I couldn't manage to get the sharp 1 mm tungsten needle to react like it did in the above video/gif.

I've been able to trace a partial current-voltage relationship though, and characteristic voltages were lower than I achieved earlier, with breakdown voltage apparently around 12–14V, and mid-point voltage below 40V. In the dotted portion current was unstable and I couldn't get reliable readings also due to a kind of hysteretic behavior.

I tried adding a short 0.3 mm titanium wire to the previously used 1 mm tungsten welding rod used as a holder. With it I swept voltage between 40V and 50V back and forth, where the cathodic plasma reaction already takes place. Titanium seems to work surprisingly well in this range, but if I switch back to lower voltages for example by turning off the bench PSU (31V) and leaving the auxiliary one (19V) enabled, where normal electrolysis takes place and current draw is in the order of a few amperes, the wire heats up considerably due to its high resistivity and can burn if current is not quickly lowered.

There appears to be a large current difference between the 49V and 50V steps. I'll try plotting the I-V curve in this region tomorrow.

Wyttenbach

The gas evolved during normal electrolysis should be generally speaking proportional to the current. In the video I posted earlier, current at 19V was in the order of 4 amperes, while at 50V during plasma electrolysis it was about 0.5–0.6 amperes. So, this could explain the observed difference in the evolved gas bubbles, if you're referring to this. If not, then I did not understand your point.

Partially wrapping the titanium wire with Cu filaments appears to have solved the overheating problems I had with it. I could now sweep voltage throughout a wider voltage range, with no overheating observed.

Since resistance at high voltages appears to rise less than it did earlier, it's likely that a part of that was due to the increasing wire resistance with temperature. Current increased and then dropped in a complex way up to mid voltages, possibly due to a combination of many changing variables. The behavior once the cathodic plasma started was more stable.

Here I swept voltage throughout the 27-50V range. I thought that shooting the video under low-light conditions would have made the plasma more visible, but the video ended up getting a bit blurry.

EDIT: the cathodic plasma reaction is at least partially driven by how much the cathode heats up (since it emits electrons), which could in part explain why the titanium wire, which acts as a resistor, appears to work well.

EDIT2: however, 26AWG Kanthal A-1 wire did not seem to work as well. A reason could be that its resistivity is very stable across a large temperature range, whereas that of titanium is strongly dependent on temperature. Unfortunately the same property coupled with the high reactivity with oxygen makes titanium a frustrating material to work with under these conditions (it breaks or burns easily).

Graphical explanation of how 50V have been obtained, since it might not be immediately obvious for people without experience with floating-ground power supplies.

When switching on the cathodic plasma from an off state, sometimes the process is not instantaneous. It appears as if heat takes a while to ramp up.

This occurs more easily when conditions are such that the applied current is higher, for example using a larger cathode and larger immersion depth, or when electrolyte temperatures are somewhat lower than usual (which leads to a higher current draw). This makes me think that resistive heating of the cathode has an influence of some sort, although it's difficult to separate this variable from other ones under these conditions.

In the gif animation below I used a 1 mm tungsten needle where this relatively quick ramping up effect is shown after switching from 19V to 50V.

I also took current-voltage measurements with it in the higher voltage region. In the last power step current increased slightly, which seems consistent with the behavior visually observed. The behavior below 30V was strange this time and I mostly omitted it from the graph.

I was curious and found that the plasma reaction appears to improve all the way to 10M KOH concentration (37.73g KOH in 67.2g tap water), although conductivity at very low voltages somewhat gets worse. So, it does not appear to be strictly a matter of electrolyte conductivity, although more testing would be needed to make sure, preferably under more controlled and safer testing conditions.

The solution, which rapidly turned dark violet-red possibly from tungsten and iron from the electrodes used, is now way too dangerously concentrated; I'm not sure if I want to keep it around in my rather unsuitable testing environment.

At this KOH concentration, there is visible cathodic plasma already at 28–29V, using the same 1 mm tungsten needle as mentioned earlier.

At higher voltages (up to 50V) the plasma looks "sharp" and at least on video it appears to emit a violet color at the highest steps. It turns more yellow as voltage is decreased. Sometimes such transition has been pointed out in related literature, but I don't recall where exactly.

5x slow-mo of the first few seconds of the above video:

EDIT: from further testing, it appears that there are improvements all the way to KOH at saturation levels, albeit with diminishing returns. Using the usual 1mm tungsten needle, I managed to get the mid-point voltage to 31V, and at 50V the cathodic plasma reaction was relatively violent, causing electrolyte droplets to get out of the glass vessel. The solution turned completely opaque dark violet and not much could be seen of what was going on with the reaction except from hints at the surface.

At higher voltages, it takes some time for the reaction to ramp up (or the electrode to heat up), and current increases similarly to what I showed earlier.

I couldn't get full I-V data for this run, but I managed to get some around the mid-point voltage. After about 38V current increased in a strange way and I stopped there since reliable measurements were not possible due to a sort of hysteretic behavior as pointed out earlier too.

Of course, at this point such experimentation becomes rather dangerous due to how caustic such concentrated KOH solution is. In the end, due to lack of suitable equipment and environment to handle this sort of experiment safely, I decided to dispose of the electrolyte solution, decontaminate the equipment used and wait for better times for more testing (or others with better equipment). I think I got good data and made interesting findings so far, though.

Since saturated KOH solution worked very well in previous tests, but was far too dangerous to use, I tried preparing a saturated K2CO3 solution and repeating cathodic plasma electrolysis with the same 1 mm tungsten needle used so far. Unfortunately overall it still does not work as good as with KOH, in that the characteristic breakdown (V_B) and mid-point (V_D) voltages are not decreased as much as with KOH.

There appears to be a blocking effect during the cathodic plasma reaction where the potassium carbonate would get precipitated out of the solution and deposit on the surface of the cathode, preventing the reaction from proceeding as intended. The electrolyte temperature in the video below was above 95 °C— close to boiling—and voltage was switched between 19V and 50V.

Temporarily restoring normal electrolysis (by lowering voltage) removes such solid K2CO3 layer and the intended operation when voltage is brought back to high levels. It could be an argument for pulsating input power.

EDIT: allowing such K2CO3 deposits to build up on the tungsten cathode at 50V during cathodic plasma electrolysis eventually shows interesting effects. Video thumbnail made at minute 2:21.