Mechanistic study of oxygen reduction reaction on a Pd/CeO2-ZrO2 catalyst

Three-way catalysts (TWCs) are widely used to convert the exhaust gases produced by internal combustion engines, including hydrocarbons, CO, and NOx, into harmless gases such as CO2, N2, and H2O. TWCs mainly consist of a metal catalyst, catalyst support, and ceramic substrate, and their performance is known to be closely related to the oxygen storage capacity (OSC) of the ceramic substrates. However, oxygen storage is a complex multi-step process that is not yet fully understood. In this study, we visualized oxygen storage at the Pd/ CeO2-ZrO2 (CZ) interface in the practical operating temperature range of TWCs using oxygen isotope quench techniques and elucidated the detailed reaction mechanism using density functional theory calculations. Pd supported on CZ promotes the incorporation of oxygen into the CZ surface. In addition, our investigation of the transport behavior of the incorporated oxygen in the bulk regime reveals that the bond strength between oxygen and surrounding atoms is weakened by Zr doping, resulting in more facile oxygen vacancy formation and oxygen migration. Our results provide useful insights that will guide the future design of highly active TWCs.