Site‐Occupation and Electron Donation by Potassium Enable Stable Metallic Silver Nanoparticles for Robust CO Oxidation

Silver‐based catalysts represent an economically attractive alternative to platinum‐group metals for CO oxidation, yet their practical application is often limited by insufficient activity and poor durability. Herein, we report a potassium‐promoted Ag/Al 2 O 3 catalyst in which K acts as a bifunctional regulator of both the structural and electronic states of Ag. Combined spectroscopic characterization and density functional theory calculations reveal that K preferentially occupies surface hydroxyl groups on Al 2 O 3 that normally serve as anchoring sites for Ag. This competitive site occupation restricts Ag anchoring and drives the formation of metallic Ag nanoparticles with optimal size. Simultaneously, the strong electron‐donating nature of K creates a locally reducing environment that stabilizes metallic Ag under oxidative conditions. As a result, the 1Ag‐2K catalyst achieves a T 90 of 250°C and maintains 100% CO conversion over 10 h of continuous operation, while K‐modified catalysts all exhibit markedly enhanced resistance to H 2 O and SO 2 poisoning. These findings uncover a cooperative site‐occupation and electronic promotion mechanism of alkali metals, providing a general strategy for stabilizing active metal nanoparticles in heterogeneous catalysis.