Influence of the Time Scale on the Reaction Mechanism of CO Oxidation over a Au/TiO2 Catalyst

Knowledge of the reaction mechanism is key for rational catalyst improvement. Traditionally mechanistic studies focus on structure and the reaction conditions like temperature, pH, pressure, etc., whereas the time dimension is often overlooked. Here, we demonstrate the influence of time on the mechanism of a catalytic reaction. A dual catalytic mechanism was identified for the CO oxidation over Au/TiO2 by time-resolved infrared spectroscopy coupled with modulation excitation spectroscopy. During the first seconds, CO on the gold particles is the only reactive species. As the reaction proceeds, the redox properties of TiO2 dominate the catalytic activity through electronic metal-support interaction (EMSI). CO induces the reduction and reconstruction of TiO2 whereas oxygen leads to its oxidation. The activity of the catalyst follows the spectroscopic signature of the EMSI. These findings demonstrate the power of studying short-time kinetics for mechanistic studies.

Automated summary

Knowledge of the reaction mechanism is essential for catalyst improvement. Traditionally, mechanistic studies have focused on structure and reaction conditions, neglecting the time dimension. In this study, time-resolved infrared spectroscopy coupled with modulation excitation spectroscopy was used to demonstrate the influence of time on the mechanism of CO oxidation over Au/TiO2. A dual catalytic mechanism was identified, with CO and TiO2 playing key roles at different stages of the reaction. These findings highlight the importance of studying short-time kinetics for mechanistic studies.