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Chemistry / Re: Is electrolysis of CO2 in a deep eutectic solvent possible?
« on: 14/07/2017 18:39:29 »
There is plenty of interesting chemistry to be done using just bulk metallic electrodes. There are various types of pre-treatments that can alter the surface (even growing nan-scale structures on the surface).
For the electrode you want to produce oxygen at I recommend using stainless steel (SS304 or 318), or nickel (platinum is also great, if you can afford it). I prepare and study catalysts that make these electrodes more efficient for oxygen production, but the naked metals themselves work quite well. Avoid carbon (graphite), copper, iron, zinc, and aluminum, all of which will degrade at the potentials required for producing oxygen.
For the electrode you want to reduce CO2 on, I would recommend testing out copper or tin (not aluminum). Steel, nickel and platinum would also be interesting. Carbon-based electrodes are commonly used, and reasonably cheap, but they also cause problems in interpreting the results (if CO2 is the only source of carbon in the reactor, you can reasonably say that any products containing carbon must have been derived from the CO2, but if your electrode is also a source of carbon, you must prove that the products are CO2 derived.)
Also, I would be careful about using choline chloride urea DES as the electrolyte. Firstly, it is likely (especially with low concentrations of water) that instead of oxygen production, the chloride ions would be oxidized to form chlorine (undesirable). And you also have to establish whether any carbon-containing products are formed from the solvent. You mentioned the wide electrochemical window, but it is also important to know where that window falls. This paper on research gate ( https://www.researchgate.net/publication/297895833_The_electrochemical_stability_of_ionic_liquids_and_deep_eutectic_solvents ) indicates that chloride ions are oxidized at 1.54 V. That is not particularly high compared to the potential of the desired reaction of oxygen production at 1.23 V... so just something to be aware of, and try not to overshoot on that end. (you've got plenty of room on the reductive side of the window)
For the electrode you want to produce oxygen at I recommend using stainless steel (SS304 or 318), or nickel (platinum is also great, if you can afford it). I prepare and study catalysts that make these electrodes more efficient for oxygen production, but the naked metals themselves work quite well. Avoid carbon (graphite), copper, iron, zinc, and aluminum, all of which will degrade at the potentials required for producing oxygen.
For the electrode you want to reduce CO2 on, I would recommend testing out copper or tin (not aluminum). Steel, nickel and platinum would also be interesting. Carbon-based electrodes are commonly used, and reasonably cheap, but they also cause problems in interpreting the results (if CO2 is the only source of carbon in the reactor, you can reasonably say that any products containing carbon must have been derived from the CO2, but if your electrode is also a source of carbon, you must prove that the products are CO2 derived.)
Also, I would be careful about using choline chloride urea DES as the electrolyte. Firstly, it is likely (especially with low concentrations of water) that instead of oxygen production, the chloride ions would be oxidized to form chlorine (undesirable). And you also have to establish whether any carbon-containing products are formed from the solvent. You mentioned the wide electrochemical window, but it is also important to know where that window falls. This paper on research gate ( https://www.researchgate.net/publication/297895833_The_electrochemical_stability_of_ionic_liquids_and_deep_eutectic_solvents ) indicates that chloride ions are oxidized at 1.54 V. That is not particularly high compared to the potential of the desired reaction of oxygen production at 1.23 V... so just something to be aware of, and try not to overshoot on that end. (you've got plenty of room on the reductive side of the window)
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