Facet engineering of α-MnO2 for directly electrocatalytic oxygen atom transfer from water toward epoxidation.

[Display omitted] • Achieving a direct olefin epoxidation with water as the sole oxygen source. • α-MnO 2 exposed with (3 1 0) facet exhibited superior activity and stability. • Oxygen vacancies played a key role in oxygen atom transfer process. • MnOOH reactive intermediate was observed in an organic electrolyte. Electrocatalytic epoxidation, utilizing sustainable water and electricity as clean oxygen source and chemical oxidant surrogates respectively, represents an attractive approach toward industrial applications. However, the low yield and selectivity of epoxides are still a formidable challenge in satisfying industrial demand. Herein, we demonstrated a crystal facet engineering strategy over α-MnO 2 catalysts for enhancing electrocatalytic epoxidation. Compared with α-MnO 2 -110 and α-MnO 2 -100, the α-MnO 2 exposed with (3 1 0) facet exhibited excellent activity. Furthermore, a 21-fold yield increase was obtained compared with the reported superior Mn-based electrocatalyst. These results revealed that crystal facet engineering could induce the formation of more oxygen vacancies and weaken the interaction of Mn-O band to regulate oxygen atom transfer capacity. In addition, the reactive intermediate (MnOOH) was observed in an organic electrolyte, which was confirmed by in situ Raman spectra and isotope labeling experiment. [ABSTRACT FROM AUTHOR]