Effect of strongly bound copper species in copper–ceria catalyst for preferential oxidation of carbon monoxide

Abstract Copper–ceria catalysts with the Cu contents up to 40 at.% were prepared by the coprecipitation method. Ammonium carbonate was used as the leaching agent on the as-calcined samples to remove the weakly bound copper species. The parent and leached catalysts were tested for the preferential oxidation of carbon monoxide (CO-PROX) reaction from 40 to 200 °C in 1%CO/1%O 2 /50%H 2 /N 2 with a space velocity of 60,000 mL h −1  g cat −1 . When the Cu doping amount reached 30 at.%, the stable and constant CO-PROX reactivity, including CO conversion and O 2 selectivity, was presented for both parent and ammonium carbonate leached catalysts. The fresh and used samples have been carefully characterized by various techniques such as power X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), transmission electron microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H 2 -TPR). It was confirmed that there are two different types of copper species, i.e. weakly bound CuO x clusters and strongly bound Cu–[O x ]–Ce structure, in both parent and leached catalysts. Furthermore, we have demonstrated that the weakly bound CuO x clusters removed by ammonium carbonate can be recovered by the migration of Cu–[O x ]–Ce species under the reduction or reaction conditions. The strongly bound copper species in CeO 2 have been identified to be the reservoir for the active Cu sites for CO-PROX.