New insights about the effect of the synthesis method on the CuOCeO redox properties and catalytic performance towards CO-PROX reaction for fuel cell applications.

The preferential oxidation of CO (CO-PROX) is promoted at the interface between CuO and CeO. For this reason, different synthesis methods of CuO/CeO catalysts have been investigated in order to maximize this interface. However, the understanding of the effect of CuO/CeO catalysts preparation method on the redox properties and CO-PROX reaction performance is still unclear. In the present work, 2 wt% CuO/CeO catalysts were prepared by four synthesis methods, namely co-precipitation with ammonium hydroxide (CP), deposition-precipitation with ammonium hydroxide (DA) or urea (DU), and impregnation (IM). The materials were characterized by XRD, SEM-EDS, H-TPR, REDOX cycles, NO passivation and applied to the CO-PROX reaction. The catalytic performance of the investigated materials was evaluated by the TOF values of CO oxidation. CuCe (CP) and CuCe (DU) catalysts were the most stable in terms of redox properties and the most active in the CO-PROX reaction. On the other hand, the CuCe (DA) catalyst presented the least stable behaviour during the redox cycles and the worst performance in CO-PROX reaction. These results clearly show that the stability of the CuO/CeO interface, submitted to successive redox cycles, plays a significant role towards the CO-PROX reaction and that this stability depends on the employed synthesis method.