Electrosynthesis of C₆ Chemicals by Propylene Oxidative Coupling on Au Surface

Electrocatalytic oxidation of alkenes represents a promising pathway for sustainable fine chemical synthesis in future chemical manufacturing. However, anodic propylene transformations typically yield only oxygenation products, such as propylene glycol, propylene oxide, acrolein, or acetone, lacking the important electro-driven C-C coupling process. Here, we report a C-C coupling pathway for propylene oxidation on Au, producing two C₆ compounds: 2,5-hexanedione and 3-hexene-2,5-dione. Under mild conditions, the total Faradaic efficiency for C₆ products reaches 36%. Combining in situ infrared spectroscopy, pressure-dependent experiments, and density functional theory calculations, it was revealed that the oxidative coupling proceeds through asymmetric coupling between *Pr and *PrOH intermediates, following the Langmuir-Hinshelwood mechanism. Simultaneously increasing the surface coverage of both C₃ intermediates is crucial for efficient C-C coupling. These findings introduce an electro-oxidative C-C coupling strategy for propylene, providing new mechanistic insights into fine chemical electrosynthesis.