Influence of the copper coverage on the dispersion of copper oxide and the catalytic performance of CuO/CeO2(rod) catalysts in preferential oxidation of CO in excess hydrogen

A series of CuO/CeO2(rod) catalysts with varying copper loadings (5, 7, 9, 11 and 15 wt %) are prepared by an ethanol thermal method and applied to the preferential oxidation of CO in excess hydrogen gas. The phase quantification obtained by XRD Rietveld refinement reveals the gradually increased copper coverage on the surface of CeO2(rod) with the increase of copper content from 5% to 15%. Moderate increase of surface copper coverage results in the increased amount of highly dispersed CuO strongly interacting with CeO2(rod) and greatly promotes the catalytic performance of CuCe(rod) for CO-PROX. However, H-2-TPR profiles before/after N2O isothermal oxidation of the catalysts reveals that the over high surface coverage of Cu atoms on CeO2(rod) leads to the reduced dispersion of CuO particles with larger size, which weakens the interfacial Cu-Ce interaction and leads to the decline of their catalytic performance for CO-PROX. Moreover, the formation of bulk phase CuO (copper loading >= 9%) has no influence on the catalytic performance of CuCe(rod) catalyst, supported by the similar catalytic performance of CuCe(rod)-11% and CuCe(rod)-15% with significantly different amounts of bulk phase CuO.