Site-Occupation and Electron Donation by Potassium Enable Stable Metallic Silver Nanoparticles for Robust CO...

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/Al₂O₃ 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 Al₂O₃ 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 T₉₀ of 250°C and maintains 100% CO conversion over 10 h of continuous operation, while K-modified catalysts all exhibit markedly enhanced resistance to H₂O and SO₂ 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.