Arraying faceted manganese oxides for selective ethylene electro-oxidation to ethylene glycol in aqueous electrolytes.

The electro-oxidation of ethylene to ethylene glycol (EG) offers a sustainable pathway for chemical manufacturing, but demands selective non-precious-metal (NPM) electrocatalysts. Here, we design and fabricate a class of arrayed Mn2O3 electrode, which shows a high EG selectivity in practically-favorable aqueous electrolytes among NPM catalysts. By screening various manganese oxides, we first pinpoint Mn2O3 to be the most selective to EG. Density functional theory calculations further reveal that the (111) facet facilitates the second OH* addition to *C2H4OH, the rate-limiting step toward EG. These fundamental findings motivate us to controllably synthesize the (111)-dominant Mn2O3 nanoarrays, which deliver a 52.6 % Faradaic efficiency for EG-the highest for NPM electrocatalysts in aqueous media. Electrochemical and operando spectral studies verify that stabilizing moderately oxidized Mn (III) state under operational anodic bias is essential to the high selectivity of EG. Our findings highlight the crucial role of Mn surface chemistry in steering alkene oxidation and advance the electrosynthesis of EG closer to practicability.