Cu-CeO2 nanocomposites: mechanochemical synthesis, physico-chemical properties, CO-PROX activity

Catalytic systems designated for preferential oxidation of CO in the presence of H-2 are prepared by ball milling of Cu and CeO2, a simple and cheap onestep process to synthesize such catalysts. It is found that after 60 min of milling, a mixture of 8 wt.% Cu-CeO2 powders exhibits CO conversion of 96% and CO selectivity of about 65% at 438 K. Two active oxygen states, which are not observed in case of pure CeO2, were detected in the nanocomposite lattice and attributed to the presence of Cu in surface sites as well as in subsurface bulk sites. Correspondingly, oxidation of CO to CO2 was found to occur in a two-stage process with T-max approximate to 395/460 K, and oxidation of H-2 to H2O likewise in a two-stage process with T-max approximate to 465/490 K. The milled powder consists of CeO2 crystallites sized 810 nm agglomerated to somewhat larger aggregates, with Cu dispersed on the surface of the CeO2 crystallites, and to a lesser extent present as Cu2O.