Three-phase electrode - Apparatus and method for electrochemical aldehyde oxidation

For many electrode materials, carbonyl compounds are electrochemically converted at high reaction rates only in very alkaline or very acidic electrolytes. But these reaction conditions also catalyze aldol condensation and other decomposition reactions in carbonyl compounds, resulting in low yields.

Researchers at Ruhr University Bochum have now developed a method that avoids electrode decomposition. It involves placing the aldehyde in an organic, non-polar phase and the hydroxide (an essential reactant) in an aqueous electrolyte. This prevents chemical side reactions in the bulk phase. To perform the electrochemical reaction, a porous, metal-coated membrane is placed at the phase boundary between the two liquids as an electrode. At the three-phase boundary thus formed, the electrode has access to both reactants and can selectively convert the aldehydes into carboxylic acid in a non-destructive manner. For example, HMF from cellulose can be oxidated into FDCA instead of terephthalic acid, which normally comes from oil.