NSR Catalysis studied using Scanning Tunnelling Microscopy

In this paper we report the fabrication of model catalysts prepared to understand the structure of the BaO surface. This utilises the ‘inverse’ catalyst method, that is, the oxide layer is fabricated onto the top of a metal single crystal surface. We show that we can atomically resolve the surface structure of BaO(111) and that it presents a (2×2) reconstruction at its surface. Under other dosing conditions we can produce a layer which is metastable at 573K, which we believe to be the peroxide, BaO₂. We have shown that the BaO layer can store NO_x from a mix of NO and oxygen, even under the extremely low exposure conditions of UHV, proving that the NOx storage process is a facile one. The results indicate that it is not necessary to have NO2 in the gas phase in order to store NO_x.