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The diesel oxidation catalysts (DOC) having high purification performance to the exhaust gas at low temperatures were investigated. In this paper two main technological improvements from conventional DOC are shown. First is forming Pt/Pd composite particles in order to suppress sintering of precious metal under high thermal aging condition. This generating Pt/Pd composite and the effect were exemplified by TEM-EDS and XRD analysis. Second is adjusting electric charge of Pt/Pd surface to reduce interaction between Pt/Pd and carbon monoxide (CO) by modifying the support material components. Adjusting electric charge of Pt/Pd surface by applying new support material could cancel CO poisoning at Pt/Pd surface. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) studies suggested that improved support material is more suitable for CO oxidation at a low temperature based on the concept.

Among the platinum group metals (PGMs), rhodium (Rh) is known as an exceedingly valuable element for automotive catalysts due to its powerful catalytic function. Because Rh is a costly material, it is paramount to enhance its catalytic function in three-way catalysts (TWCs). This work reports results on the palladium (Pd)-Rh combination which assists the catalytic function of Rh. XPS and XRD are used to observe the Rh characteristics, and engine dynamometer and vehicle testing are conducted to measure catalytic performance and quantify the emission benefits of the Pd-Rh interaction in TWCs. It is well known that Pd-Rh forms a core-shell structured alloy with Rh in its core. This alloy exerts a large negative impact on NOx performance. However, it is inferred from our analyses that highly-dispersed Pd and Rh particles within a certain Pd/Rh atomic ratio prevent this deterioration phenomenon.