Nafion membranes are used to separate the two electrochemical cells in the CO2 reduction experiments. Can anyone explain what is its role in CO2 reduction experiments?
As the others said, separation of products is the main purpose, to prevent their loss due to crossover.
A critical requirements is also to support the transport of H+ from the anode to the cathode, where H+ is a reactant in the CO2 reduction reactions. This completes the electro-chemical circuit in a sustainable way. However, this is often overlooked. Many researchers use Nafion which is a cation exchange membrane. But in the pH ~7 solutions usually employed, the effective H+ concentration is ~10-7 M, whereas the electrolyte cation concentration (K+, Na+, etc) is usually far far higher (often 0.1-1 M, depending on the concentration used). Depending on the relative transference numbers, the primary species transported through the membrane is likely the alkali cation, not H+, and therefore the cell will be dialysed under operation, an unsustainable configuration.
An anion exchange membrane could be more suitable, but then organic anions produced by CO2 reduction (formate, acetate) could be lost across the membrane as well.
Dear Santosh
In case of aqueous electroreduction of CO2, the oxygen evolution takes place at the anode electrode, and the reason for the separation is to prevent further oxidation of the desired products formed from CO2 reduction.
Hope you find this helpful
Good luck!
-Amir
As the others said, separation of products is the main purpose, to prevent their loss due to crossover.
A critical requirements is also to support the transport of H+ from the anode to the cathode, where H+ is a reactant in the CO2 reduction reactions. This completes the electro-chemical circuit in a sustainable way. However, this is often overlooked. Many researchers use Nafion which is a cation exchange membrane. But in the pH ~7 solutions usually employed, the effective H+ concentration is ~10-7 M, whereas the electrolyte cation concentration (K+, Na+, etc) is usually far far higher (often 0.1-1 M, depending on the concentration used). Depending on the relative transference numbers, the primary species transported through the membrane is likely the alkali cation, not H+, and therefore the cell will be dialysed under operation, an unsustainable configuration.
An anion exchange membrane could be more suitable, but then organic anions produced by CO2 reduction (formate, acetate) could be lost across the membrane as well.
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