Hello everyone!
I am posting again to kindly ask for your experienced opinion. We are setting up a system with a Ga WE, Ag CE and Ag/Ag+ RE. Initially, we were going to use AgNO3 for our RE compartment.
We are making it in house and we are worried that any nitrate leaking out of the GW in-house frit we are using will form a complex with Ga (GaNO3). We are experience a reaction where WE surface smoothness is essential.
I am looking into alternatives such as AgPF6 because we do not think that PF6- would form a complex with Ga. I have only seen it in literature being used as a supporting electrolyte, so I was wondering
1. What you think about this choice.
2. If you have any other electrolytes to suggest for our research purposes.
Thank you!
Michela
I have previously used a silver wire immersed in a solution of 0.1 M AgNO3 in MeCN and capped with a BAS Vycor tip as the RE for electrochemical measurements involving air sensitive anions in THF. I believe this type of RE is standard for many nonaqueous electrochemical cells, but nitrate anion can create difficulties due to its oxidizing nature (some nitrate inevitably leaks into the cell). An alternative to nitrate might be generally useful here. It’s possible that silver methanesulfonate could work. The internet (including the new AI’s) indicates that silver methanesulfonate is not soluble in acetonitrile, but there is literature that contradicts this. I once put together a review of the use of metal methanesulfonates as reagents in simple chemical transformations, and there are several literature mentions of the use of silver methanesulfonate in MeCN. Generally, the MeCN was dried prior to use. This review was never published in a journal, but I put it online to make it available for whomever might find it valuable. I can’t recall if I ever tested the solubility of silver methanesulfonate in MeCN myself, but it is probably worth a quick trial. Tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, and/or hexafluoroantimonate are also possibilities, but the inevitable fluoride anion in equilibrium with the main species could be an issue.
Hi Michela Cavalieri
I was about to suggest methanesulfonate, then I saw that Michael Gernon has done it already...
I agree that choosing a fluoro complex such as PF6(-) carries some risk of fluoride interference, especially if another ion with affinity to fluoride - such as Ga(3+) - is present. Compounds in which fluorine is covalently bound in a way that's not prone to dissociation, such as silver trifluoromethanesulfonate or silver trifluoroacetate, may be preferable.
One might try different silver alkanesulfonates (e.g., ethanesulfonate, propanesulfonate, etc.) in order to get the best result. The attached pdf gives a brief description of the structure of typical soluble silver compounds. The attached patent describes the preparation and use in electroplating of some less common soluble silver salts/compounds.
To replace AgNO₃ in MeCN for your RE compartment with a Ga working electrode, choose an inert, non-coordinating electrolyte that won’t interfere with RE ions or corrode Ga.
Recommended Electrolytes:
• [nBu₄N][BF₄] – Stable, inert, good solubility in MeCN.
• [nBu₄N][PF₆] – Similar to BF₄⁻ but less soluble.
• [nBu₄N][NTf₂] – Very inert, ideal for sensitive systems.
• Avoid Ag⁺, halides (Cl⁻, F⁻), and coordinating anions like NO₃⁻.
These tetraalkylammonium salts are electrochemically inert and safe for use with Ga and RE ions in MeCN.
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