Unraveling Sintering Mechanisms of Precious Metal Catalysts in Diverse Gas Environments

Heterogeneous precious metal catalysts offer the highest selectivity and activity in chemical production and combustion by-product reduction reactions. However, their efficiency is hindered by sintering, particularly in high-temperature oxidizing environments such as automotive emissions control. To address this issue, we investigate the sintering mechanisms of platinum on alumina support in various exhaust gas environments at different temperatures using <i>in situ</i> environmental scanning transmission electron microscopy (STEM). We observe that the presence of both oxygen and water vapor significantly accelerates sintering, while water vapor alone has minimal impact. Our study unveils transient nanoparticle shape instability, indicating rapid particle migration, in an oxygen and water vapor environment, contrasting with stability in a vacuum. This underscores the complex interactions between platinum, the alumina substrate, and gases, providing essential insights for the design of improved catalysts for industrial applications.