Effective Improvement of Pt Catalyst for Exhaust Gas Purification by Using the Highly Crystallized CeO 2 as an Additive

Over the last few decades, Pd-based three-way catalysts (TWCs) have been more extensively used than Pt-based TWCs because of their higher thermal stability. In this study, the addition of CeO 2 to a Pt-based TWC was performed to improve the reductivity and dispersion of Pt particles after aging at 1000 °C. The aged dispersion of the Pt-loaded CeO 2 was much higher than that of a commonly used La 2 O 3 –CeO 2 –ZrO 2 catalyst. Furthermore, the hydrogen temperature-programmed reduction conducted on Pt/CeO 2 revealed that the Pt-loaded highly crystalline CeO 2 (HC–CeO 2 ) exhibited a higher reductivity as compared with that of the high surface area CeO 2 (HS–CeO 2 ). Adding a small amount of HC–CeO 2 to the Pt-based TWC increased both the Pt dispersion and reductivity after aging. Owing to the high dispersion and reductivity of Pt, Rh/Pt-based TWCs with HC–CeO 2 used as an additive to the Pt catalyst layer demonstrated a higher catalytic activity than that of the Rh/Pd-based TWCs even after aging at 1000 °C in an exhaust gas.