Electrolysis of Carbonic Acid

[Mr Skeptic]

Can you use carbonic acid for electrolysis, and what would you get if you did? Would using carbon electrodes make this more interesting?

[CaptainPanic]

First of all: I am not sure about this how it works in practice. What I wrote here might only work on paper (I just don't know)... I think you'll need a couple of fancy catalysts. If you just take some electrodes and stick those into water with CO2 dissolved in it, something will happen, but I doubt you'll reduce the CO2.

 

I think you should take CO2 as starting point, not the carbonic acid. CO2 and carbonic acid are in equilibrium anyway (CO2 + H2O <--> H2CO3)

 

I think this is a set of half reactions that can occur if you apply the right potential (?).

 

CO2 + 2e- + 2 H+ --> HCOOH (formic acid)

(google: formic acid CO2)

 

HCOOH + 2e- + 2 H+ --> H2C=O (Formaldehyde, note: toxic!)

(google: formic acid formaldehyde, and try to find the reverse reaction (not the oxidation)).

 

H2C=O + 2e- + 2 H+ --> CH4O (methanol, note: also toxic )

 

Searching Google, I found that finding the oxidation reactions is relatively simple. (Oxidizing is also energetically easier...). The reverse, so from CO2 to methanol, is more tricky.

[Dan Frederiksen]

it seems it is much easier to first split the water and then combine the hydrogen with CO2. a simple copper or zinc catalyst with the two gases will produce methanol. I don't know the precise details of the process but it will probably be heated. nobel prize winner George Olah wrote a book called Beyond gas and oil: the methanol economy where he mentions several specific processes for making methanol from hydrogen and CO2. it has been done industrially since 1920

 

there are even ways of capturing CO2 from the air so we can make fuel for cars and power plants with only water and air and power from windmills or the sun

Edited September 21, 2009 by Dan Frederiksen
typo