Cobalt Oxide Anodes

Circling back five months into the PbO2 thread seeking convergence huh ? Long live the marathon blog

The cobalt spinel portion of the "ceramic bronze" mixture will still be what is forming the boundary layer , the conductive interface with the titanium substrate . The TiO2 will simply function as a dopable thixotropic thickener for the cobalt .

One of the earliest Co related patents US4115239 that I looked at used something similar as a build coating , but IIRC the interface on the Ti was still a direct application of cobalt . See example 2 .

previous attachment:
US4115239 Baked Co(NO3)2 Direct Coated Titanium anode.pdf (65.57 KiB)
http://www.sciencemadness.org/talk/viewthread.php?action=att...

Many of the Dow patents related to the spinel directly
formed on the Ti as the interface formed from baking .
It can be used on top of DTO , and can possibly be used underneath it as well , but that is not established yet
AFAIK .

Thanks jp - see the "more on PbO electrodes" thread for the initial discussion of cobalt oxide anodes.

Here's an image of my simple 200ml chlorate cell running with the single cobalt oxide spinel coat over Ti anode. After 7 hours it is still stable, it's running in constant current mode and the voltage topped out at 4.0 Volts after a couple of hours. The black slime around the top looks worse than it really is, it's spread out by the bubbles and the meniscus. I wish I'd taken a photo of the anode before putting it in the cell, but too late now, I'm not going to touch it...

Edit: That SS canister in the background is completely separate and is not wired to the cathode of the chlorate cell, it just looks like it is because of the camera angle!

Regards, Xenoid

[Edited on 2-12-2007 by Xenoid]

Howdy Folks,

Good idea.
Wonder what Janger would make of the new thread!

Good and bad news.
My Cobalt Oxide (plated) on DTO'ed Ti has made Perchlorate. I got a purple color with Methylene blue test.
Since DTO does not seem to be capable of making Chlorate it is surly the Co Oxide.
The bad news is that all the Co Oxide has stripped off. It lasted a few hours. No good, it was only a thin coat but a thicker (8 hours plating) would not last much longer.
The DTO is still soldiering on.

The more you think about the baking (as opposed to plating) the simpler you reasize it is. Once you have an oven (a shambolic one like I have is sufficient) your in business.

The attached file is from Kirk Othmer, may be of some use.

Dann2

Attachment: cobalt.pdf (162kB)
This file has been downloaded 3160 times

I give up on the electrodeposition idea.

The Dow Patents

From page 8 (for me anyways) of 'More on PbO2 anodes' thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=2465&a...
__Quote__________________________________________-
That specific anode was only used for two batches of perchlorate, starting from NaClO3, which means that is has seen about 200 hours of use at a current of 35-40 A. It still looks pretty much exactly the same. I have made other anodes (using the same process) that I've used in chlorate cells for hundreds of hours with no visible signs of wear.
______________________________________________

Since the guy does not write patents I am inclined to believe him. He is a guy who I communicated with many moons ago about LD anode. He had (the only person I ever knew) some homemade Graphite Substrate LD Anodes that were long lasting and were a success. Interesting to note that even he moved from Graphite to Ti.

I do intend to hopefully do some Cobalt baking. Have no nitrate and may take a trip to ceramics store to purchase some Co Carbontat or make some from Co SO4 + CaCl2.

Right now I am still bogged down in DTO stuff + I want to wheel out the LD tank.

Regarding getting Perchlorate with Co Oxide I am not now 100% sure if it was the Co Oxide or DTO that has made the Perchlorate. I have been running the same cell with a DTO Anode in it (just testing the DTO anode) and the Perchlorate concentration is rising (as seen by a drop of Methylene blue.
DTO does not appear to make Chlorate (or at least it is very bad at it, as a chlorate cell (300ml) that I have ran for 50 hours at 0.5amps will not give a ppt of K Chlorate when some K Chloride is added). Yet it appears to make Perchlorate. It may be making very little Perchlorate though as the Methylene blue test is very sensetive.

Dann2

combining technologies

There's a variation on the theme which hasn't been tried
and very well may work .

I refer to US6228241 attached

Suppose we don't hydride , but simply etch with oxalic acid
and rinse off with distilled water . A thin but pore filled
passivation layer begins to form on the Ti immediately . Now suppose that this sample of Ti is then made the cathode for a brief time in the cobalt nitrate electrolyte . Where is the first place that atoms of cobalt metal are going to deposit but at the most conducting spots , which just happens to be at the bottom of those pores in the TiO2 layer that is growing .

The little deposits of Co metal will immediately stop the further growth of that virgin TiO2 or actually Ti mixed oxide
which resides at the bottom of those pores . And this doesn't take very long either , a few seconds to a few minutes , no longer , creates those cobalt metal plated
pore bottoms .

Now the current is reversed , and the process of US3399966
is carried out . When the current is reversed the mesa of TiO2 begins to grow in thickness under the anodic oxidation ,
but it is also behaving as a reverse biased diode whose
valve metal behavior makes it conduct poorly from the start
and even more poorly as time passes and its thickness increases . But happily nearby down at the bottom of pores
is some freshly deposited cobalt metal that is conducting just fine in the anodic direction , and filling up that pore
with a growing column of electrodeposited cobalt suboxide . The rate at which that column of cobalt suboxide grows in height is faster than the rate at which the mesa of TiO2 is growing , so in time the column of cobalt suboxide reaches the surface and then spreads across the mesa blanketing the whole surface into which it is keyed with all those filled pores .

At this point we remove the sample of Ti , and let it soak
in a heated bath of saturated Co nitrate for awhile , and then bake it . This strategy should produce a very adherent and well doped coating . The tenacious habit of the TiO2 itself as well as the porosity of the TiO2 layer is exploited , as well as the electrical properties . This might work very well since it exploits the natural behavior and properties of the materials .

You could come back over the top of this with a vitreous
SnO2 and Co3O4 combination . And it might be good to go
at that point as a finished anode . Looks good on paper
and in theory to me . And I haven't seen such a process
described anywhere .

BTW , Dow and BASF are the two largest chemical technology
corporations on planet earth . And that technology involving
the pores and mesas is compliments of NASA , who occasionally think outside the box . Putting these three technologies together makes sense . No guarantee that
Ti will follow the model of Al , but they are both valve metals ,
and they both have porous oxide coatings , so there's a very good chance it will work .

[Edited on 4-12-2007 by Rosco Bodine]

Attachment: US6228241 Electrically_conductive_porous_anodized_aluminu.pdf (87kB)
This file has been downloaded 986 times

Well guys! The cobalt oxide spinel coated "5 minute" anode has been running for 48 hours (2 days) now, at 1 Amp (~50mA/cm^2) the voltage has risen slightly again, it's now 4.3 Volts. This is not surprising because it is starting to look the worse for wear!

Edit: Actually, now that nearly half the active coating has worn away, I guess it's running at closer to 100mA/cm^2.

I removed the anode, rinsed it, dried it with warm air and took the images seen below showing both sides. What is left of the cobalt oxide is still well bonded, but smudges to produce an incredibly black smudge (like carbon black), this is sort of like a reactive top layer.

When I put it back in the cell, quite vigorous bubbles began to issue from the surface with no connections made - weird, this is strange stuff, highly catalytic perhaps, able to split water into H2 and O2 maybe, with unlimited energy for all, but I digress...!

When connected up, and I set the current for 1 Amp the voltage has gone back up to 4.2 V and the cell is continuing as before, although there seem to be more bubbles coming from the anode!

I am finding this is really interesting!

I've sort of purified some cobalt nitrate, and I intend to do a triple coat with a concentrated solution, to see how it goes!

Edit: I forgot to point out, that the electrolyte level is only a bit above half way, its below the area where the smudge marks are, and can just be made out as a faint line with a colour change.

Regards, Xenoid

[Edited on 4-12-2007 by Xenoid]

[Edited on 4-12-2007 by Xenoid]

Looks like a good early "proof of concept" experimental result . Anything which doesn't passivate immediately
or within a few minutes is moving in the right direction

Wonder what alternating coats of Co(NO3)2 and a low temp decomposing SnO2 precursor might do , with the Co being the first coat and the last , making a sort of sandwich . Maybe ammonium stannate would do the trick
or any syrupy hydrosol form of the Sn . There is a tin nitrate and this could work also , mixed with the Co nitrate .

Tempil heat indicators might be very handy for the
heat curing process .

http://www.tempil.com/product_display.asp?form.findapp=206

http://www.tempil.com/company.htm

[Edited on 4-12-2007 by Rosco Bodine]

Attachment: Tempilaq.pdf (516kB)
This file has been downloaded 1349 times

I just went to have a look at my semi-purified Co nitrate solution, which I had left in the fridge, only to find that it has crystallised....
I've poured off most of the supernatant liquid and I will add a small quantity (a few mls) of water to these crystals to make up my next coating solution. Only a small amount of water is needed because they just about dissolve in their own "water of crystallisation".
The image below shows about 20g of crystals of cobalt nitrate hexahydrate sitting in the bottom of a 100ml beaker, which is lying on its side.
To get this stuff to recrystallise requires having just the "right" concentration level before cooling in a fridge.

Edit: I forgot to mention that the Co nitrate solution is kind of interesting in that it's thermochromic (is that a word). When it's boiling it's a intense purple, beetroot juice, K-permanganate colour but when it's cooled down to 0 oC or -10 oC it's more of a reddish colour like strawberry syrup. Don't leave it lying around where there are little kids, they might drink it!

Regards, Xenoid

[Edited on 4-12-2007 by Xenoid]

Well, I've pulled the plug on the cobalt oxide anode after almost 3 days. There wasn't much point in continuing to run it (other than making chlorate.. ). It is obvious that a single coat is not thick enough to form a practical anode. I also wanted to leave a bit of the coat in tact so I could have a good look at it.

Just to confirm, however, it is well bonded to the Ti. It's actually a bit difficult to describe what it is like, perhaps a bit like a sooty or smoke coating on metal. It's not really hard, but you can't rub it off either.... anyway, more later.

Regards, Xenoid

There's new ideas worth exploring with experiments here . And if nothing else it may be prophylactic regarding
the experimenters risk of potential antimony and/or lead poisoning Heck I was about to suggest the possibility
for the mixed valency precursor with stannic oxide , having
cobalt nitrate as the bivalent metal component . Or perhaps the possible complexation of cobalt nitrate in an ammonium stannate mixture , or perhaps a cobalt nitrate
mixture with stannic oxalate . Even looked a bit at the
possibilty of a stannic nitrate derived mixture in combination with cobalt nitrate . There's plenty of novel experiments which could be done along new lines ,
rather than just trying to copy any one process which may be incomplete in its method or disclosure .

Looks like what you had going there is very promising .
Nothing to be discouraging there for the one coat .
Try three Got tin? maybe try a sandwich coating .

using tin oxide alone may not be so simple

When pool chlorinators go bad!

Ho, ho, ho! Christmas arrived early for me this year, and I finally got a present I wanted!

This is a bit off topic, but doing the rounds of the swimming pool maintenance companies looking for used pool chlorinators has finally paid off. I went to a small company I hadn't visited before, the guys were sitting around having morning tea (as they do). I explained what I was after and why I wanted them, only to be greeted with blank looks. Then one guy said "Oh, didn't we just throw one in the skip over there'! We had a look and it was still there. They said they didn't get many, but when I said I would give them $10 for one they seemed quite enthusiastic and took my name, phone number and email. I got the one in the skip for free. They said it was a "self cleaning model" but something obviously went very wrong with the circuitry. It's a 6 electrode model and the electrodes still "look" OK, nice and black. I'm not sure what the pale blue stuff is, I assumed it was copper stained salt, but it didn't taste very salty! Anyway I don't particularly care. As a first step in cleaning it up I've left it soaking in water, I'll see how that goes!

Edit: I think the gunk is Na2CO3, it fizzes when a few drops of HCl are poured on it. Here in NZ, Na2CO3 is used as a "pH increase", the pool owners probably added too much. I think the blue colour (which is fairly superficial) is just a water colouring to make the pool look better.
All the electrodes appear to be coated, I guess thats the case with a self-cleaning chlorinator, in that the polarity is switched on a regular basis. It has 25 stamped on the top and the leads are pretty grunty so it may be a 25 Amp model.
I think I'll sit it in some vinegar to clean it up, nice and mild!

Ho, ho, ho, Xenoid

[Edited on 5-12-2007 by Xenoid]

For a gaggle of various spinels of possible interest not necessarily just cobalt spinels , see US3711382 . Sheesh
there is a couple of pages long list of these spinels , enough to keep a minerologist busy for a lifetime .

I read a brief mention that spinels can be baked directly onto hydrided titanium , in a patent from a different source than the patent jpsmith123 posted in starting the TiH2 thread .

@jpsmith123 , Did you try to do any of the baked coatings onto hydrided Ti ? The interface layer is everything ,
and once that is sealed off nicely by the first coating ,
and retaining conductivity , then you should be able to apply whatever else sort of wear coating you want ,
by whatever method . Maybe the MnO2 plus PbO2
low baked onto the TiH2 , then followed by the Co
acetate or nitrate as subsequent coatings could give
good results .

@Xenoid , About the open circuit gassing that you observed
from the spinel put back into the brine , it is probably the
catalytic decomposition of hypochlorite to free oxygen and NaCl . That's what happens if the spinel is in contact with
hypochlorite , and it may even hapen with other oxidizers ,
so when the current is off , you probably don't want to leave
the "decomposition catalyst" in the cell , because it makes
the powered on reaction run backwards when the power is off

[Edited on 5-12-2007 by Rosco Bodine]

Quote:

Originally posted by Rosco Bodine @Xenoid , About the open circuit gassing that you observed from the spinel put back into the brine , it is probably the catalytic decomposition of hypochlorite to free oxygen and NaCl . That's what happens if the spinel is in contact with hypochlorite , and it may even hapen with other oxidizers , so when the current is off , you probably don't want to leave the "decomposition catalyst" in the cell , because it makes the powered on reaction run backwards when the power is off

Rosco, I guess you are right about this! One of the first things I did was to put the anode in plain water, the result was nought, zero, nil, nothing, nada! So I guess no free energy for all, at least not yet...

Where's the cheapest place to get lead now ,
Toys 'R Us ?

Xenoid the way you describe your baked on coating...well it sounds exactly like my best electrodeposited coatings...and I have to say I don't like it .

I think Rosco's right in his implication that the trick (if there is one) is in the interface layer.

Rosco I haven't tried anything recently with a hydrided layer, but I'm preparing one now (it's been cathodized all night at about 30 mA/cm^2).

Anyway, I know when I plated a layer of plain cobalt (from Co Acetate solution) it was extremely adherent to the Ti (only sandpaper would take it off), but I was not able to oxidize it just by heating it with the heat gun. It would apparently have to be baked for 8 hours or so at 350 degrees Centigrade to accomplish that.

Quote:

Originally posted by jpsmith123 Xenoid the way you describe your baked on coating...well it sounds exactly like my best electrodeposited coatings...and I have to say I don't like it . I think Rosco's right in his implication that the trick (if there is one) is in the interface layer.

Some Papers I'd Like To Look At

I wonder if anyone has access to the following papers? These sound like they may have some useful information.

###################################

A new cobalt oxide electrodeposit bath for solar absorbers
Solar Energy Materials and Solar Cells, Volume 51, Issue 1, 1 February 1998, Pages 69-82
Enrique Barrera, Ignacio González and Tomás Viveros

A study was carried out in a Hull cell in order to optimize the deposition conditions of cobalt xide (black cobalt) in an electrolytic bath, which uses cobalt nitrate for direct
obtention of black cobalt. Thermal stability of the material was surveyed on several samples of black cobalt prepared on stainless-steel with a thickness of approximately of 2.5 μm. It
was found that the optical properties change, in respect to the initial values, with time of treatment until an equlibrium is reached. This equilibrium depends on the substrate and the
temperature of the treatment used.

##############################################################################

Black cobalt solar absorber coatings
Solar Energy Materials, Volume 22, Issue 4, August 1991, Pages 293-302
S. John, N. Nagarani and S. Rajendran

A new electrolyte has been proposed for the deposition of black cobalt selective absorber coatings. These coatings are used in solar collectors for photothermal conversion of solar energy. We have studied the influence of electrolyte composition and operating parameters on the properties of the black cobalt coatings including optical (α, ε and electcical properties. Thermal stability and corrosion resistance tests showed good durability of black cobalt selective coatings for high temperature applications.

##################################################################################

Preparation of selective surfaces of black cobalt by the sol-gel process
Renewable Energy, Volume 9, Issues 1-4, September-December 1996, Pages 733-736
E. C. Barrera, T. G. Viveros and U. Morales

Black cobalt, Co3 O4, thin solid coatings on stainless steel and glass substrates have been prepared by the dip coating technique via the sol-gel route using a CoCl2 precursor. The
coatings produced on substrates exhibit a blue to black colours as a function of the film thickness. Sols have been made from a cobalt acetate precursor 0.1 M, and for such conditions, the dip coating process gives 0.08–0.25 μm thick uniform films per dipping, depending on the viscocity of the sol.


###################################################################################

Cobalt oxide thin films prepared by chemical vapor deposition from cobalt (II) acetate
Solar Energy Materials, Volume 23, Issue 1, November 1991, Pages 25-29
Toshiro Maruyama and Tsuyoshi Nakai

Cobalt oxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method. The raw material was cobalt (II) acetate which is non-toxic and easy to handle. Polycrystalline films were obtained at a reaction temperature above 300°C. From near-normal reflection measurements it follows that the films have solar absorptance α = 0.73 and thermal emittance ε = 0.089.

##################################

Xeniod that so-called "stain layer" you refer to is exactly what's underneath my electrodeposited coatings as well.

As I mentioned, my coatings didn't actually passivate, but rather, I removed them from the brine and wiped them and the coating came off like slime, all except for that blue, stained appearance, that is. At that point I sanded them and recycled them.

[Edited on by jpsmith123]

excerpt from cobalt article

http://www.1911encyclopedia.org/Cobalt


@jpsmith123 , the following is the one to get

The Real McCoy???

Firstly, I have checked the calibration of my thermocouple/multimeter using ice/water, boiling water and molten lead - amazingly it was within a couple of degrees for all three.

1) Ti rod was spun in drill press and "sanded" with 100 grit garnet paper for 1 min.

2) Ti rod was immersed in hot concentrated (290g/L) HCl in a test tube sitting in a beaker on a hotplate for 30 mins. Vigourous bubbling ensued and the HCl turned mauve. Actually, I think this is overkill, probably 5 or 10 mins would be fine!

3) Another test tube was filled to an appropriate level with a solution comprising approximately 20g cobalt nitrate hexahydrate and 20 mls of water.

4) The rod was dipped in the solution for 15 seconds, shaken several times and placed in the previously described heat-gun set-up for 10 mins at a temperature of 370 oC. +/- ~ 10 oC. The rod was then allowed to cool to room temperature (about 8 mins).

5) This procedure was repeated 4 (four) times, with the 4th run lasting for 60 mins. (1 hour).

The main differences in this procedure as compared to my first attempt are;

1) More dilute and purer coating solution.
2) More coats, 4 vs. 1
3) Slightly higher temperature 370 vs. 350 oC.
4) Last coat was baked for extended time, (this is in the patent, I had forgotten about it)

This has produced the anode shown below;

In retrospect I think that an even more dilute soln. may be called for, it is amazing how black the initial coat is, given how little soln. appears to be clinging to the surface. This may produce an even more homogenous coat.

@jpsmith123 - Note this coating is tough, it cannot be wiped off, there is just a slight grey smear on ones finger after it is repeatedly rubbed up and down. The first anode used too strong a soln. and produced a thick, "fluffy" coating. This looks like the real thing.

I've put it in a new cell and ramped the current up to 50mA/cm^2 (1.65 Amps) the voltage was about 3.2 (very low). I've turned it down to about 5mA/cm^2 to "run it in" for an hour.

I will report back with initial perfomance figures in a short while!

Hello Folks,

Anode looks good.!

I purchased some Cobalt Carbonate, Zr Oxide and Antimony Oxide in ceramcis store so hopefully will get some thing done in near future. I have Zinc powder + Nitric acid.
Got a bit bogged down with other work last few days.
The DTO coat on Ti still going strong. (Approx. 120 hours) I put up the current density to hurry up it's destruction. The damm thing will still be going at Christmas at this rate.
It is making Perchlorate.

Following thread with interest.
Has Spinel Cobalt Oxide 'Holy Grail' status? Now THERE is a question.

@JP
You could try asking in the reference section for the paters. I Solo cannot do it, nobody can do it.

Ha! Xenoid busted Rosco I got one of those Fluke digital multimeters too that has the thermocouple input plugs ....
and now I know a good use for it . Heat gun here I come Need to make a little trip to the building supply tool department . Got money burning a hole in my pocket right now for parts and such .

Got drill press Ever used that cloth backed emery ribbon
they sell by the foot ? It's just like the sheet stuff but is about an inch and a half wide ribbon . Plumbers use it on copper pipe to scuff it for soldering . Makes quick work
for polishing a rod in a drill press when you see saw it back and forth . The filings fall right out of it as it goes so it doesnt load up the grit and keeps cutting , doesn't get hot in
one spot either .

How about three or four Halleluiahs ! It looks like the real deal . I bet this thing's right .

Yeah I think Xenoid just nailed it . ( Knock on wood )

[Edited on 6-12-2007 by Rosco Bodine]

Sorry to take a while getting back but I've been coating another anode using different conditions.
The anode has been running for 3 hours now and everything looks fine, the voltage even dropped slightly as the cell warmed up!
I didn't bother with the conditioning, that only lasted for 15 mins. The anode is running at ~50mA/cm^2 its somewhat longer than the previous one, the active area is about 33 cm^2 and I'm running it at 1.66 Amps. Cell volume is about 400 mls, anode - cathode distance ~4.5 cm.
I'm limiting the current a bit, because it's running in my "electronics lab" which is totally enclosed with no ventilation. There is a little bit of black scum on the surface of the electrolyte, but I don't think it's anything to worry about!

If my guess is right , because of the electrocatalytic effect
of the cobalt , no additives like fluorides or persulfates
will be required for the perchlorate production , and the
cell efficiency will be higher , lower operating voltage
for the cobalt spinel anode than other anode materials . No need either to make the chlorate first , separate and then make perchlorate , it should go all the way from the plain chloride to the perchlorate , to a high degree of completion .

Might be interesting to put a bit of lithium chloride
into the cell to test earlier speculations about it possibly
being catalytic via continual metathesis for a KCl starting solution .

Of course you would need some cell depth below the
electrodes so the rising layer of KClO4 crystals doesn't short out the cell . Probably a circulating pump having an intake tube near the bottom could be used to keep the crystals suctioned out and trapped on a filter or in a settling tank in the return stream . You could run a
smallish sized cell like a gallon jar , and keep replenishing the pumped electrolyte water and chloride , while the KClO4 accumulates in a picnic cooler where you scoop it out occasionally with a snow shovel and deposit it in
a nearby wheelbarrow to drain and dry

[Edited on 6-12-2007 by Rosco Bodine]

Steady on, Rosco, lets not get too carried away...

For anyone out there...... is there anyone out there, other than we intrepid four, and the honourable Mr Wang!

Here is my primitive heat gun set up! The rod just sits at an angle, upright at the bottom of the Al tube. I hold the rod in place on the heat gun and lower the tube over it so only one part of the rod touches at the top and one at the bottom.

Whilst making my latest anode I dropped it and it rolled across the concrete floor, there wasn't a mark on it!

This is not the ideal set up by any means, I'm still looking at toaster ovens. I will report back when I've done a bit of construction/destruction.

Oh Yeah! Good luck!

It's a 2000 Watt model.

Something I forgot to mention! I have been putting the dipped, wet anode directly in the gun and turning the heat upto full. I did this because in the patent they said to put the anode straight into an oven. The two new anodes I have made today are a bit streaky and patchy, I think it would be best to gently dry them first in warm air whilst rotating, this should produce a more even coat.

I was thinking if these work out, and last for a run or two, the cost is negligible! Once you have purchased your Ti, this coating only costs about 20 cents in chemicals and electricity and the Ti will last a lifetime...

Hello,

Can't see the bottom of the Heat gun but have you it a bit off the ground. It will burn out if there is not a good flow of air through it. (Hope I am not stating the obvious.)

The DTO was done the way of the Diamond Shamrock patents using the same amounts of SnCl4:5H20, Antimony,
HCl, and Methanol.
Will right up exactly what I did but I do not think my exact procedure is important.
It is interesting to note that all patents use SnCl4:5H2O when making DTO as an undercoat for something (let it be LD or CO) but there is a procudure in pat No. 3627669

C:\Documents and Settings\me\Desktop\Page download\top\Top\chlorate\leaddiox\us3627669.html

for an actual DTO only anode.

This uses SnCl4 (anhydrous) refluxed with Amyl Alcohol.
It must be better than the stuff (not really an anode, but just an undercoat) produced via SnCl4:5H2O but the DTO produced usins hydrated SnCl4 must be better as an undercoat. Just guessing, reading between the lines.

Perhaps we need a DTO thread

My cell, the one testing the DTO, is now giving a 'yougart' product (lots of K. Perchlorate) when a sample it taken out and some KCl added to it.

Dann2

It's designed to sit on the ground, it has a built in stand, the air inlets are on the side!

Here is the anode I coated this afternoon, I made the cardinal sin and changed 3 variables simultaneously, otherwise same as above:

1) Etching was carried out for only 15 mins.
2) Solution concentration was halved.
3) Doubled the coatings to 8

It doesn't look all that different to the previous anode. I'm going to put it in a perchlorate cell and see how it performs. The coating may be slightly harder ie. no force in the known universe is capable of removing it -

You know what it reminds me of - that black (antirust) coating on structural steel. I assume it's magnetite (another spinel). Might be worth trying iron nitrate solution and giving the Ti a magnetite coat!

Pretty much yeh! I think with these type of coatings there will always be a little "dust" on the surface. I have actually wiped this one quite vigourously with a wet paper towel, virtually nothing came off. I thought I'd give it a good clean, so I wouldn't get any black scum on the surface like the previous anode.

To free up my lab power supply for testing the perchlorate cell, I have moved the chlorate cell over to a 5 volt (constant voltage) computer supply. I've put a 0.8 ohm 20 watt resistor in series. It is now running at 3.22 volts and 1.86 Amps. Still looks fine!

The new anode I made this afternoon is now in a small perchlorate cell (250 mls) near saturated NaClO3, no additives. I've got more adventurous with this and upped the current to ~100mA/cm^2. It is running at 4.7 volts and 2.2 amps. I hope its making perchlorate, its certainly making some ozone!

Well what a day! I'm gobsmacked...

I just hope its all going in the morning!

nickel cobalt spinel versus zinc cobalt spinel

Cobalt sol spontaneous from acetate solution

Look who's talking

Hard for kids to sleep around Christmas

It looks like the spinel is for damn sure a good interface ,
but how it will endure in the long run as an actual
wearing coating in perchlorate cell service is another matter .

It may be that PbO2 perhaps hardened with Bi will
need to be overplated to make a more permanent anode .
Just can't find any good data on perchlorate cell longevity
for the spinel , but seems like I have seen it once somewhere
that one combination did hold up well in perchlorate service .

Anyway the interface is the hard part , and it looks like that is at least one big headache and really core component that
very likely now has a solution .

Humble Pie!

Oh dear!...

The last anode doesn't appear to be holding up too well in a perchlorate cell. There is a lot of black crap floating around, although the anode is still coated and producing from the whole surface!

Maybe I overdid it at 100mA/cm^2, I think I'll turn it down to 50mA/cm^2.

Note: On the second page, in the part 2 Experimental section:

........baked in air at 200 oC - 400 oC for 5 MONTHS.....

I surely hope this is a typo, poor proof reading!

I think they mean 5 minutes....

Yeah electricity must be really cheap in Tibet or
wherever that translation came from That
would be a whole lot of light bill and oven time .
Maybe it was cold in the lab and such an experiment
became a scientific mandate as a countermeasure
for prevention of cryogenic castration .

I got some more articles requested that are relevant to
these type coatings . Found out you can't mix the
tin oxides precursors with the cobalt spinel precursor
because on baking the cobalt must have air exposure to
complete its oxidation , and tin oxide stops that oxidation before it completes . So you can use the layers applied
one over the other , but each must be baked separately
to completion before the next layer goes on . It looks like about 450C is the upper limit for the Co3O4 and past that
it decomposes to its separate oxides .

Also found out you definitely can combine electrodeposition methods with baking methods .

More later .

Quote:

Originally posted by dann2 The DTO coat on Ti still going strong. (Approx. 120 hours) I put up the current density to hurry up it's destruction. The damm thing will still be going at Christmas at this rate. It is making Perchlorate.

@ Dann2 - What's the current density and voltage on that anode, you probably mentioned it somewhere, but I can't be bothered searching for it!

It's too early to give up electrodeposition!

more on sol gel derived Cobalt spinel

Electrodeposition of Co oxides

Pyrolytic decomposition of Cobalt Nitrate

sneaking suspicion about polymer thickening

Hello,

Current density is low on my DTO anodes.
30mA per square cm for first 100 hours or so. I have double this to approx. 60mA now going ok.
Voltage was rock steady at 5 volts at the lower corrent density.
It was about 6 volts at 60mA per square cm. The voltage is going up now a small amount. Dont know if it the andoe starting to fail or the fact there the cell is becoming a finished Perchlorate cell.

BTW Magnetite is a reverse spinel, not a Spinel. It is important to get our facts right. :-|

Dann2

In Search of the Holy Grail - Not!

Well, I think to be practical, 50mA/cm^2 is a lower limit, with 100mA/cm^2 desirable!

Still off topic but...

Here's my pool chlorinator electrode assembly after cleaning the Na carbonate off with dilute HCl (the vinegar idea just didn't cut the mustard). This model sells for about A$400 new. The outside surface of the two outside electrodes still has 100% MMO (multi-metal oxide) coating, the rest of the electrode surfaces look to be roughly 75% worn out! It will be a bit difficult to disassemble because the top of the electrode straps and electrical connections are embedded in epoxy. The plastic straps around the electrodes are also epoxied in place but should be removable. I think I will just snip the electrode straps at the point where they enter the epoxy. I can then get an engineering shop to spot weld some additional Ti strap onto the stubs to make them into usable chlorate cell electrodes. They can also re sandblast them so I can put a new coating on them like.... like.... like.... cobalt oxide

Anyway, 6 Ti mesh electrodes (200mm x 65mm) for nothing, can't complain about that!

@ Rosco - Yeah, the voltage was rising rapidly and it was passivating. I had another play around with it at high voltage and high currents. I didn't get any useful information from the exercise, but I managed to generate a strange corrosion hole at one point about 4mm wide and ~.5mm deep in a VERY short time. I've had to file the surface to smooth it over - bugger!

cell electrolyte additives

summary of previous information