Title: Phase Coexistence and Structural Dynamics of Redox Metal Catalysts Revealed by Operando TEM

Abstract: Metal catalysts play an important role in industrial  redox reactions. Although extensively studied, the state of these  catalysts under operating conditions is largely unknown, and assignments  of active sites remain speculative. Herein, an operando transmission  electron microscopy study is presented, which interrelates the  structural dynamics of redox metal catalysts to their activity. Using  hydrogen oxidation on copper as an elementary redox reaction, it is  revealed how the interaction between metal and the surrounding gas phase  induces complex structural transformations and drives the system from a  thermodynamic equilibrium toward a state controlled by the chemical  dynamics. Direct imaging combined with the simultaneous detection of  catalytic activity provides unparalleled structure–activity insights  that identify distinct mechanisms for water formation and reveal the  means by which the system self-adjusts to changes of the gas-phase  chemical potential. Density functional theory calculations show that  surface phase transitions are driven by chemical dynamics even when the  system is far from a thermodynamic phase boundary. In a bottom-up  approach, the dynamic behavior observed here for an elementary reaction  is finally extended to more relevant redox reactions and other metal  catalysts, which underlines the importance of chemical dynamics for the  formation and constant re-generation of transient active sites during  catalysis.

链接：https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202101772

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