Deactivation Mechanism of a Au/CeZrO₄ Catalyst During a Low-Temperature Water Gas Shift Reaction

On-stream deactivation during a water gas shift (WGS) reaction over gold supported on a ceria−zirconia catalyst was examined. Although the fresh catalyst has very high low temperature (<200 °C) for WGS activity, a significant loss of CO conversion is found under steady-state operations over hours. This has been shown to be directly related to the concentration of water in the gas phase. The same catalyst also undergoes thermal deactivation above 250 °C, and using a combined experimental and theoretical approach, a common deactivation mechanism is proposed. In both cases, the gold nanoparticles, which are found under reaction conditions, are thought to detach from the oxide support either through hydrolysis, <250 °C, or thermally, >250 °C. This process reduces the metal−support interaction, which is considered to be critical in determining the high activity of the catalyst.