Investigation of ammonia oxidation over copper with in situ NEXAFS in the soft X-ray range: influence of pressure on the catalyst performance

The oxidation of ammonia over polycrystalline copper was investigated by me ans of in situ NEXAFS (near-edge X-ray absorption fine structure) spectrosc opy in the soft X-ray range. The reaction, carried out in a 1 : 12 excess o f oxygen, was observed by mass spectrometry. The simultaneous detection of the surface electronic structure and its catalytic performance allows corre lation of different reaction products to the current surface structure of t he catalyst. It is shown that a change in total pressure from 0.4 to 1.2 mb ar severely affects the reaction path. Copper(l) nitride was identified as poison and a copper oxide was found to be the active phase for the selectiv e oxidation of ammonia to nitrogen.