Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
Electrolysis cell design
I have been playing with basic cell constructions lately and want to get some input on things I need to consider when designing cells for high yeald
low reaction time. I have a mechanical background with a full workshop at my disposal so can design and make any configuration.
Obviously surface area of anodes is a key to high yeald but what about spacing of electrodes? When we for example consider a bank of flat graphite
anodes. How far apart would they need to be ?
Could they be stacked + - + - + - similar to a wet cell battery with say a 3mm gap between each anode.
[Edited on 3-2-2015 by Muzz1969]
|
|
|
m1tanker78
National Hazard
Posts: 685
Registered: 5-1-2011
Member Is Offline
Mood: No Mood
|
|
What are you electrolyzing and to what end? If, for example, you're reducing silver ions to metal, your plates need to be far enough apart that they
won't short out with the metal dendrites. Another important general consideration is when your cell produces gas at one or both electrodes. Sometimes
bubbles tend to cling to the electrode(s) or accumulate air pockets which increases localized current density on the parts that aren't covered in
bubbles.
Chemical CURIOSITY KILLED THE CATalyst.
|
|
|
Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
Not anything in specific but firstly I'm playing with oxidation of primary alcohols
The unit I want to build will have a stirrer unit attatched so bubble formation shouldn't be an issue....As I build the unit I will post pictures. I
am currently making the first unit with 10mm x 200 x 10 off round electrodes and I'm planning on a flat anode configuration for my second unit.
[Edited on 3-2-2015 by Muzz1969]
|
|
|
macckone
International Hazard
Posts: 2159
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
Planning an electrolysis cell without a clear goal is like
picking a vehicle for transportation without knowing
where it is going. Just getting on a random bus
isn't going to get you to Hawaii. I am pretty sure
you would need a plane or boat for that.
Figure out what you want to produce and then design
a cell. Your first goal seems to be oxidation of alcohols.
That means your cathode for the hydrogen generation
should probably be carbon as it won't catalyze a reverse
reaction. Your anode probably needs to be platinum or
something similarly catalytic. Using a divided cell will
help prevent your alcohol from being hydrogenated.
Spacing for this application needs to be lower than
electrodeposition. You may also need to encourage
flow around your electrodes. With a divided cell, that
means you need two pumps. And if you are using a
divided cell, you also need a membrane. Of which
there are many kinds for specific chemical applications.
|
|
|
Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
@macckone...ok well I'll start with the oxidation of primary alcohols.
So a few questions,
Why platinum? (I know it is a good non reactive material for anode use, but why use it over say a graphite anode)
Is the alcohol placed on one side of the membrane and the electrolyte on the other side of the membrane?
What type of membranes are there ? I can think of one such type that is used as separators in lead acid batteries. Are we looking for something that
allows electrons to pass through but will not let the electrolyte and alcohol mix?
|
|
|
macckone
International Hazard
Posts: 2159
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
Platinum is just one possibility. It is an good multipurpose catalyst
Where as carbon is usually not catalytic.
Alcohol and a suitable conductive solvent is placed on one side
While an electrolyte solution is placed on the other.
There are a lot of membrane types. Nafion is one brand.
|
|
|
Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
With electrolyte choice , for example in the case of ethanol all the reactions I have read regarding this , they are mainly using dichromate, I have
also read that these reactions can also be done in the presence of iodine or bromine. Would the elemental form need to be used or the salt form would
be acceptable.
[Edited on 4-2-2015 by Muzz1969]
|
|
|
macckone
International Hazard
Posts: 2159
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
Dichromate is one of the catalyst I am familiar with.
No clue on bromine or iodine but I suspect the salt
Would be oxidized and that would oxidize the alcohol.
|
|
|
pepsimax
Hazard to Self
Posts: 74
Registered: 30-7-2013
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Muzz1969  | @macckone...ok well I'll start with the oxidation of primary alcohols.
So a few questions,
Why platinum? (I know it is a good non reactive material for anode use, but why use it over say a graphite anode)
Is the alcohol placed on one side of the membrane and the electrolyte on the other side of the membrane?
What type of membranes are there ? I can think of one such type that is used as separators in lead acid batteries. Are we looking for something that
allows electrons to pass through but will not let the electrolyte and alcohol mix? |
Graphite is messy, i'd use an anode bag for it. In my experience (mainly plating, never done any proper electrochemistry) it can easily flake off tiny
carbon particles. An anode bag can easily be had by searching for a 10 micron diesel filter bag on ebay or amazon.
|
|
|
Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
Ok, so I have built a test cell with a PTFE divider. I am using graphite for both rods to start with. I have used filter paper as the salt bridge
between the two cells.
I have place ethanol + water in one cell and sodium dichromate + water in the other cell
The cell is drawing 200mA @ 12 v
The Ethanol is bubbling away with the dichromate appearing static
Can anyone tell me if this is correct in the way I have set it up.
|
|
|
TheChemiKid
Hazard to Others
Posts: 493
Registered: 5-8-2013
Location: ̿̿ ̿̿ ̿'̿'̵͇̿̿з=༼ ▀̿̿Ĺ̯̿̿▀̿ ̿ ༽
Member Is Offline
Mood: No Mood
|
|
Try this video.
When the police come
\( * O * )/ ̿̿ ̿̿ ̿'̿'̵͇̿̿з=༼ ▀̿̿Ĺ̯̿̿▀̿ ̿ ༽
|
|
|
Muzz1969
Harmless
Posts: 37
Registered: 19-11-2014
Member Is Offline
Mood: No Mood
|
|
@chemkid....sorry but what does making hydrogen have to do redox reaction of ethanol
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
