Surface species changes over ZrO₂ modified Cu catalysts in the process of reduction and reaction

Cu model catalyst was prepared through thermal decomposition method and ZrO₂/Cu was obtained through impregnation method. The morphology and surface composition of the catalysts were investigated using SEM and XPS. Surface specie changes over Cu and ZrO₂/Cu in the process of the reduction were investigated using in-situ Raman. In the mean time, CO and H₂O were passed through in sequence, and the Raman spectra were recorded. The results show that surface of Cu mainly consists of CuO species while that of ZrO₂/Cu contains rich surface hydroxyl groups besides CuO species. ZrO₂/Cu is easier to be reduced to CuO with ZrO₂ species agglomerating to floccus state. However, Cu₂O formed over Cu catalysts after reduction. CO adsorption over Cu produces Cu-CO with the disappearance of Cu₂O and production of CO₂. Water is weakly adsorbed over Cu but is adsorbed strongly over ZrO₂/Cu to produce Cu₂O species via Cu-OH intermediate.