Enabling Al sacrificial anodes in tetrahydrofuran electrolytes for reductive electrosynthesis

Abstract

Addition of halide salts as co-supporting electrolytes is a simple electrolyte tailoring strategy for enabling Al sacrificial anodes in THF-based electrolytes.

Overview of Recent Scale-Ups in Organic Electrosynthesis (2000–2023)

“…Issues related to robustness such as electrode fouling/corrosion − can also impact the viability of a large-scale electrochemical process. The identity of the supporting electrolyte or additives can help to minimize electrode fouling. − Ideally, the electrochemical process should not be highly sensitive to adventitious water and oxygen in order to enable process robustness. Another desirable feature is that the end-of-reaction mixture should be stable, ideally both toward overelectrolysis as well as after the electrolysis is completed.…”

A guide to troubleshooting metal sacrificial anodes for organic electrosynthesis

“…97 For a more in-depth understanding of the surface reaction, X-ray photoelectron spectroscopy (XPS) provides information about the chemical environment of each element within the top 5–10 nm of the surface film. 91,98 XPS is useful for determining the identity of the surface species and for characterizing extremely thin surface films, such as the oxide layers formed when Mg and Al are exposed to oxidants.…”

“…4a shows an example of an LSV experiment designed to assess metal stripping at an Al electrode. 91 When a TBABF 4 supporting electrolyte in tetrahydrofuran (THF) is used, the oxidative current density is extremely low and no Al oxidation is observed due to the formation of a passivating film resulting from a chemical reaction between Al and the electrolyte. The current density also decreases upon subsequent scans, indicating that Al stripping becomes more difficult due to the growth of the passivating film.…”

“…This sharp polarization and extreme overpotential at the anode indicate that the oxidation reaction does not proceed smoothly, likely due to the presence of a passivating surface film. 91 Monitoring both the cathode and anode voltage during electrolysis requires the use of a nonaqueous reference electrode and a potentiostat equipped with the hardware necessary to record both the working and counter electrode potentials.…”

“…The beneficial effect of additives is not limited to bromides in this case; Cl − -, Br − -, and I − -containing additives all enabled Al oxidation. 91 …”