CuMn(2)O(4) nanocatalysts synthesised by silica aquagel confined co-precipitation were analysed for the preferential oxidation of CO at different temperatures and concentration conditions The catalysts show a higher activity than copper-ceria catalysts synthesised by the same method but, like these, they suffer from slow deactivation during the reaction. Surface analysis (FTIR and XPS) was used to unravel the deactivation mechanisms Gradual reduction of the catalysts by the carbon monoxide present in the PROX stream was concluded to be the main cause of deactivation (C) 2009 Professor T Nejat Veziroglu Published by Elsevier Ltd. All rights reserved