What is an efficient way to generate CO2 electrochemically?

I would like to build a small carbon dioxide generator for experimental purposes. There are two requirements that are set in stone:


1. It has to be electrochemical. (Easy to switch on/off with electricity.)
2. It has to generate only one gaseous product, which is carbon dioxide. (No need to separate the gases, which might prove difficult.)


I have thought and tried using oxalic acid in a cell with a proton exchange membrane, which did not work. (And I have not figured out why so far.) I kept generating oxygen instead of carbon dioxide. Also the byproduct was hydrogen, which is problematic in my application, and the PEM is very fragile, so I could not build up any pressure. There are a few requirements, that are debatable. For example if a reactant or product is highly toxic or extremely expensive, that would possibly be a dealbreaker. Also it would be nice to be able to enclose the cell and build up a bit of pressure with carbon dioxide (only 1-2 bar).


Unfortunately researching this is rather difficult, since the main topic of research is binding carbon dioxide, which are 99.9% of the publications that pop up with the keywords I have searched for. Are there other things I could try? I have not tried a lot and I am already running out of ideas, but please bear with me, I am a theoretician and have not been in the lab for quite a long time.




The [Kolbe electrolysis](https://www.organic-chemistry.org/namedreactions/kolbe-electrolysis.shtm) may be helpful to you. It is an electrochemical decarboxylation process with free radicals as intermediates, with applications in [syntheses of symmetric alkanes](https://www.sciencedirect.com/science/article/abs/pii/S1572665718303643).  

![pic](https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/62/topics/reaxys/rf_431/m_rf_431.svg)
  

$\ce{H2}$ is generated as a side product on the cathode, but using aprotic solvents or a substance with a higher reduction potential than that of $\ce{H2}$, like $\ce{CuSO4}$, should fix this. Alternatively, as suggested by Poutnik, consider separating the compartments with a porous glass.


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