A noble-metal-free electrocatalytic system for direct synthesis of α,β-unsaturated carbonyl solids in aqueous solution†

Abstract

The α,β-unsaturated carbonyls are important precursors in pharmaceuticals, plastics, and lubricants. While traditional condensation of aldehydes and ketones requires extensive separation due to unwanted self-condensation of carbonyls, oxidative condensation of alcohols requires organic solvents and costly homogeneous catalysts. Electrochemical oxidative condensation of alcohols provides an alternative solution for the synthesis of α,β-unsaturated carbonyls, yet the performance needs to be enhanced for practical applications. Here, we present a two-electrode system for oxidative condensation of alcohols in aqueous KOH electrolyte, which enables direct synthesis and collection of α,β-unsaturated carbonyl solids under ambient conditions using low-cost electrocatalysts. The anode is a calcined NiFe layered double hydroxide (LDH), which promotes the oxidation of alcohols and avoids the oxygen evolution reaction from water oxidation at a low bias. The cathode is a CuFe-LDH that displays a decent HER performance and avoids the hydrogenation of the generated product. Additionally, the basic electrolyte accelerates the condensation of carbonyl intermediates into corresponding α,β-unsaturated carbonyl solids. The system only requires a voltage of 1.6 V for the synthesis of a variety of α,β-unsaturated carbonyls, rendering it a promising solution for sustainable synthesis.