Ce-Zr-Cu mixed oxides as catalysts for on-board H2 purification by preferential CO oxidation

The on-board H2 production for polymer membrane fuel cells (PEMFCs) is usually accomplished by a multi-step process that includes catalytic reforming of hydrocarbons or alcohols followed by preferential oxidation of CO (CO-PROX) at low temperature. Among different types of catalysts for the PROX reaction, those based on Ce-Zr-Cu oxides [1,2] have shown promising properties in terms of activity, selectivity and resistance to CO2 and H2O. In this work, a series of Ce–Zr–Cu mixed oxide systems was prepared by slow co-precipitation, with the aim to investigate the influence of the presence of very small amounts of zirconium on the catalytic performances of these three-component catalysts. Their activity was evaluated in the preferential oxidation of CO in hydrogen-rich gas stream (1.2% CO, 1.2% O2, 50% H2, He balance and 1.2% CO, 1.2% O2, 50% H2, 15% CO2, 10% H2O, He balance). Correlations between catalytic activity and physico-chemical properties of the materials were made by using X-ray powder diffraction (XRPD), N2 physisorption, temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS). We observed that the physico-chemical properties and catalytic performances of the studied systems, with a very low amount of zirconia, were highly dependent on the Zr/Ce atomic ratio and that ceria, doped with an optimal amount of zirconium, can give rise to a material with enhanced reducibility of copper oxide improving its dispersion and its interaction with CeO2.