【Frontiers in HaiChuan Chemical Technology】Progress achieved in the study of electronic structure regulation of metal catalysts at East China University of Science and Technology

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Recently, Professor Duan Xuezhi and Special Researcher Chen Wenyao from the School of Chemical Engineering at East China University of Science and Technology have made significant progress in the field of regulating the electronic structure of metal catalysts. The research team proposed and developed a completely new \"electron fence\" strategy, which enables effective control of the electronic states of the active sites on gold by precisely assembling metastable rhodium atomic layers at the gold-molecular sieve interface, thereby significantly enhancing the activity and selectivity of the propylene epoxidation reaction. The relevant findings were published in the Journal of the American Chemical Society, and the team was invited to create the journal cover. Gold catalysts exhibit unique advantages in green transformation processes such as the selective oxidation of olefins, owing to their ability to inhibit deep oxidation reactions. However, gold’s limited ability to activate H2 and O2 significantly restricts its intrinsic activity in reactions such as one-step epoxidation of propylene. Although traditional bimetallic alloying strategies can enhance the reaction rate, they often lead to the occurrence of side reactions, resulting in excessive hydrogenation of propene to propane or its over-oxidation to CO2, thereby compromising the reaction selectivity. Therefore, maintaining high selectivity while enhancing the catalytic activity of gold remains a key scientific challenge that needs to be addressed urgently in this field. To address this challenge, the research team broke away from the conventional design paradigm that relied on the exposure of active metals, and proposed an \"electron fence\" strategy centered on electron confinement control. By precisely controlling the reduction kinetics of the immiscible Au–Rh precursors, a metastable \"hamburger-like\" heterostructure was constructed at the Au/TS-1 interface, allowing rhodium atoms to be selectively embedded and concealed within the gold-support interface. On the one hand, this structure spatially prevents the rhodium sites from directly participating in the reaction ； On the other hand, an interface \"electron fence\" is formed at the electronic level, effectively restricting the loss of electrons to the carrier and causing gold to transition from its common Aum+ state to a more reactive Aun− state. A combination of various in-situ and quasi-in-situ characterization techniques (AC-HAADF-STEM, XAFS, XPS, in-situ infrared) along with classical molecular dynamics and density functional theory calculations revealed the formation mechanism and stability of this metastable structure. Studies have shown that an appropriate amount of rhodium can induce the formation of a stable \"hamburger\" configuration at the nanoscale, whereas an excess of rhodium causes the structure to transition to a ball-cup or Janus configuration, exposing the active sites of rhodium and triggering side reactions. By precisely controlling the Au–Rh ratio, an optimal synergy among the structural configuration, electronic state distribution, and catalytic performance was achieved. In terms of performance, the electronic fence-type Au–Rh/TS-1 catalyst achieved a production rate of 502.6 gPO•kgcat-1•h-1 in the propylene epoxidation reaction. Mechanistic studies further indicate that the electron-rich Aun− site significantly promotes the synergistic activation of H2 and O2, enhancing the formation of the key reactive intermediate •OOH, which has been identified as the core reactive species driving propylene epoxidation. Furthermore, this \"electronic fence\" strategy shows good scalability; it also led to an increase in both activity and selectivity in the selective oxidation of propane to **, providing new approaches for the design of high-performance selective oxidation catalysts.