Tailoring the Electronic Metal‐Support Interactions in Supported Silver Catalysts through Al modification for Efficient Ethylene Epoxidation

In this work, we synthesized an Ag/Al−MnO₂ catalyst by metal-modification engineering to simultaneously improve the catalytic activity and selectivity for ethylene epoxidation. Experimental and theoretical results showed that the Al modification tailored the 3d state of Ag on MnO₂ through strong electronic metal-support interactions (EMSIs). These targeted effects enhanced the catalytic selectivity and overcame the activity–selectivity trade-off in heterogeneous catalysis, providing a new strategy for designing advanced catalysts for heterogeneous oxidation reactions.

Abstract

Metal-modified catalysts have attracted extraordinary research attention in heterogeneous catalysis due to their enhanced geometric and electronic structures and outstanding catalytic performances. Silver (Ag) possesses necessary active sites for ethylene epoxidation, but the catalyst activity is usually sacrificed to obtain high selectivity towards ethylene oxide (EO). Herein, we report that using Al can help in tailoring the unoccupied 3d state of Ag on the MnO₂ support through strong electronic metal-support interactions (EMSIs), overcoming the activity-selectivity trade-off for ethylene epoxidation and resulting in a very high ethylene conversion rate (~100 %) with 90 % selectivity for EO under mild conditions (170 °C and atmospheric pressure). Structural characterization and theoretical calculations revealed that the EMSIs obtained by the Al modification tailor the unoccupied 3d state of Ag, modulating the adsorption of ethylene (C₂H₄) and oxygen (O₂) and facilitating EO desorption, resulting in high C₂H₄ conversion. Meanwhile, the increased number of positively charge Ag⁺ lowers the energy barrier for C₂H_4(ads) oxidation to produce oxametallacycle (OMC), inducing the unexpectedly high EO selectivity. Such an extraordinary electronic promotion provides new promising pathways for designing advanced metal catalysts with high activity and selectivity in selective oxidation reactions.

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