Structural and catalytic aspects of sol–gel derived copper manganese oxides as low-temperature CO oxidation catalyst

The influence of the preparation method on structural properties and on the catalytic activity of sol–gel derived binary copper manganese oxides for CO oxidation in dry air at room temperature has been investigated. The catalysts were characterised by means of BET and X-ray diffraction. All results were compared with a commercial Hopcalite sample. Subsequent conventional optimisation of the most active sample – prepared by the so-called ethylene–glycol method (EG I) – including compositional and calcination temperature variation revealed Cu20Mn80Ox (EG I) calcined at 400 °C as very active catalyst. Sintering processes induced by the crystallisation of the amorphous material above 400 °C cause a dramatic decrease of the catalysts’ surface area accompanied by deactivation. XPS data recordings were used to investigate the oxidation states of the metals in this catalyst and in the reference material. In conclusion a combination of high surface area, amorphous state and the presence of Cu2+ and Mn3+ was found to be essential for the high catalytic activity of the binary copper manganese oxides. The reactivity of the best catalyst was tested under application-relevant conditions, i.e. in moist air and at low-temperature fuel cell conditions.