XPS study on barium-promoted copper chromite catalysts

Copper chromite catalysts are used nowadays in catalytic reactions during the incineration of organic air pollutants, which is a subject of growing interest in environmental safety. The aim of this work was to investigate by XPS the surface species, on a sample prepared by ourselves and to study the modifications of these species after various heat treatments. This study confirmed the deep surface transformation on the sample. We observed a complete reduction of the copper atoms from oxidation state II to I. In contrast, this behaviour is not followed by the chromium atoms, which are reduced to oxidation state III only to a small degree. This fact could be explained by the presence of barium which was introduced as a promoter in the catalyst.