NOx storage in model Pt/Ba NSR catalysts: fabrication and reactivity of BaO nanoparticles on Pt(1 1 1)

We have employed high temperature scanning tunnelling microscopy to probe the adsorption of Ba on Pt(1 1 1) and its reactivity towards oxygen and NO. The aim of this work is to study the NOx storage process. A novel approach to prepare a model of the NOx exhaust catalyst has been used rather than the conventional deposition of a metal onto an oxide substrate. Ba grows on the Pt(1 1 1) surface in a Stranski–Krastanov mode, at high doses Ba nanoparticles are formed on a thin layer of Ba. The storage component of the catalyst has been prepared by reaction with oxygen at 573 K, which produces particles of BaO. The reactivity of this surface towards a mixture of O2 and NO results in a dramatic increase in particle size which is attributed to the storage of NOx in the form of the nitrate, Ba(NO3)2.