Catalytic reduction of NO in vehicle exhaust plays an important role in reducing NOx which is a major atmospheric pollutant. Although the three-way catalyst for stoichiometric gasoline-fueled vehicles has been commercialized worldwide, this material cannot be applied to oxygen-rich exhaust emissions such as those from diesel and lean burn engines. The selective catalytic reduction of NO with NH3 (NH3-SCR), which is also in practical use for NOx removal emitted from large-scale boilers, can be applied to oxygen-rich exhaust. However, the use of NH3 as a reductant is difficult for vehicle applications. In this regard, a great number of studies have been conducted on the use of hydrocarbons as a reductant for the selective catalytic reduction of NO (HC-SCR) in oxygen-rich atmospheres [1], [2] and [3], since the first reports by Iwamoto et al. [4] and Held et al. [5] following the patents of Volkswagen [6] and Toyota [7]. Many kinds of catalysts based on zeolite [8], metal oxide [9] and noble metals [10] have been reported to show activity for HC-SCR. Nevertheless, practical application of HC-SCR has been difficult due to its insufficient performance in real life applications.