Hydrothermal Aging-Induced Changes in Washcoats of Commercial Three-Way Catalysts

In order to quantify hydrothermal aging effects on the mono- and bi-metallic Pd and Rh supported on cerium-zirconium promoted alumina commercial three-way catalysts (TWCs), the catalysts were tested both fresh and after accelerated hydrothermal aging. The catalytic tests showed clear deactivation of the aged samples and influence on TWC's property, such as: light-off temperature, specific surface area (BET), dispersion of noble metals, oxygen storage capacity, oxygen storage capacity complete and labile oxygen storage capacity. Water inhibition have been investigated and confirmed for the performance of NOx reduction of the fresh catalyst. X-ray photoelectron spectroscopy was used to study changes in the oxidation state of the Pd and Rh present in the washcoat of the catalyst, before and after hydrothermal aging. Element maps by SEM-EDX analysis was perform in order to characterize the catalysts morphology, the surface's composition and element distribution.