Au-Ni Rotating Ring–Disk Electrode (RRDE) study: A new and rapid screening technique for quantitatively detecting aldehyde during electrochemical alcohol oxidation reaction

Abstract

Many high-value compounds are derived from aldehydes, which are typically synthesized with stoichiometric amounts of costly reagents. It is therefore desirable to achieve the preparation of aldehydes via the reagent free, electrochemical oxidation of primary alcohols. This requires an understanding of the effect of reaction parameters (e.g. electrolyte pH, type of alcohol, electrode material, potential etc.) on the aldehyde yield and therefore a method for the online quantification of formed amounts of aldehyde during electrochemical alcohol oxidation.Here, we present a new, easy-to-use rotating ring-disk electrode (RRDE) method that allows determination of the aldehyde yield without any need for advanced equipment. By comparing the results of the RRDE method against labor-intense and tedious methods such as semi-online HPLC analysis (here presented for the first time as well) and differential electrochemical mass spectrometry (DEMS) we show that the RRDE method determines the aldehyde yield reliably and accurately. A key advantage of the method is its speed: studies that would require days to conduct with the aforementioned techniques, can be conducted within hours using the RRDE method. Furthermore, the RRDE method overcomes limitations of offline methods such as HPLC and GC-MS analysis that are typically used to quantify the reaction products of electrochemical alcohol oxidation: in the alkaline electrolytes required for alcohol oxidation aldehydes decompose (partially) before analysis is conducted and it is therefore not possible to determine the aldehyde yield accurately. Finally, the RRDE method does not require advance equipment and can be adopted by most electrochemistry labs around the world.