V activated Ag-O catalytic sites for direct electro-epoxidation to successive producing propylene oxide

Abstract As one environmentally friendly and sustainable method, direct electrooxidation of propylene (D-EOPO) can successively produce propylene oxide, but the poor selectivity and activity of the catalyst hinder the application. To overcome the issues, a D-EOPO device based on a membrane electrode reactor (MEA) has been developed with optimized Ag-V-O/GDL catalyst to active oxygen formation for propylene epoxidation. In-situ spectroscopy and theoretical calculations have revealed the critical role of introduced V, which can accelerate the formation of Ag-O to decrease the generation energy barriers of O* from absorbed water on the catalyst surface. Moreover, the V doping also can attribute to a positive shift of the d-band center of Ag, and facilitate the adsorption of propylene on the active center. Thus, the formation of the key intermediate (OC3H6*) by coupling O* with adsorbed propylene is synergistic promoted, thereby enabling the efficiency of D-EOPO. Finally, the MEA reactor with the developed Ag/V bimetallic catalyst have been developed for continuous D-EOPO, which can steadily electrooxidize propylene to PO with a yield of 64.48 µmol/h over 72 hours (almost the highest among currently reports).