Please tell me what possible processes occur during background electrolysis: acetonitrile, electrolyte TBAP 0.1M at potential -1.9 V (Ag/AgCl)? Acetonitrile for HPLC.
Hello,
My experience in this field has led me to consider the following processes: dielectric polarization, space charge formation, energy transfer, losses, electric field polymerization and discharges. You can find details by following the links below:
Project 1. SURFACE and BUIK BREAKDOWN PHENOMENA https://www.researchgate.net/project/SURFACE-and-BUIK-BREAKDOWN-PHENOMENA
Project 2. INSULATING MATERIALS PROPERTIES AND RELIABILITY https://www.researchgate.net/project/INSULATING-MATERIALS-PROPERTIES-AND-RELIABILITY
Project 3. INSULATING MATERIAL EXPERT SYSTEMS https://www.researchgate.net/project/INSULATING-MATERIAL-EXPERT-SYSTEMS.
https://doi.org/10.1063/1.5047673
Sincerely
Claude Le Gressus
Can you specify the current density and the electrode materials? Provided actual window opening CVs would be even better. I assume that TBAP is Tetrakis 4-Benzoic Acid Acid Porphyrin ( and not a tetrabutylammonium phosphonate) , and that there is also a solvent and a background electrolyte?
Yuriy Tolmachev TBAP is a tetrabutylammonium hexafluorophosphate.
Cell: undivided, ElectraSyn 2.0, WE CE - Pt (Pt plated Cu electrodes), Ag/AgCl.
Solution: Acetonitrile, 0.1 M TBAPF6.
Potentiostatic electrolysis of background: -1.8 V, 2,2F/mol (Under these conditions, our substance is reduced).
Why does the background undergo changes under these conditions? (electrochemical window is -2.8V according to CV)
Dear Natalia V. Zolotareva ,
possible spinoff processes[1] might switch on from the:
a) water (humidity) contamination[2], and/or from the
b) dissolved oxygen content[2].
Also, an additional contamination issue might originate from your RE (reference electrode)[3].
1. Pop up of i (current), near the potential -1.9 V (Ag/AgCl).
2. https://www.researchgate.net/post/What-is-the-role-of-Tetra-butylammonium-cation-TBA-in-the-cyclic-voltammetry
3. Can I use aqueous reference electrodes for non-aqueous solutions?
Aqueous reference electrodes can be used in non-aqueous solutions in many instances, but problems can arise. First, junction potentials can be quite large for non-aqueous solutions, so comparison of redox potentials between aqueous and non-aqueous solutions (and between different non-aqueous solutions) requires an internal standard. Second, salts from the electrolyte solutions can precipitate in the frit, leading to increased noise in the current response. For example, if a perchlorate salt is used in the analyte solution, and a potassium solution is used in the reference electrode, potassium perchlorate can precipitate in the frit. This problem is decreased in BASi® reference electrodes by using sodium chloride in silver/silver chloride reference electrode, since sodium perchlorate is more soluble than potassium perchlorate. Third, since water and chloride ions can diffuse through the frit into the analyte solution (albeit slowly), aqueous reference electrodes are not suitable for water and chloride sensitive analytes. https://www.basinc.com/products/ec/faqele#Aqu_Org
Ioannis Samaras Thanks a lot. I also thought about it, but I do not know how to check these factors.
A picture is worth a thousand words... actually more than a thousand in many cases. Since you mentioned HPLC, I assume that you are interested for the potential region within the electrochemical window of your solvent+ background electrolyte. I assume that your background currents are uA/cm2 ...
In this case, the most common cathodic process in AN is the reduction of H2O and O2. As their near-electrode concentration changes (due to natural convention, for example), the background current changes too. Another interesting thing is a change in the resistance between working and ref. electrodes (e.g. as such effluent composition changes). This results in a charging current artifact, if a potentiostat is used. If you looking at nA currents, this charging can be comparable to the signal.
Yuriy Tolmachev Background currents are around 1 microampere (CVA). But during electrolysis on the Electrasyn 2.0, the currents grow relatively quickly, the solution becomes cloudy, and a precipitate forms. I guess the reason is in the electrodes...so the working electrode is Cu plated Pt
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