Revealing the synergy between zinc and aluminum in Cu/ZnO/Al 2 O 3 industrial catalyst.

The active sites in Cu/ZnO/Al 2 O 3 industrial catalyst for CO 2 hydrogenation to methanol need to be fully clarified. In this work, we reveal two types of active sites at the nano-sized Cu/ZnO interface, of which only one type is efficient. The efficient active site is characterized by isolated and under-coordinated Zn atoms located at the vertices of the supported ZnO island, thus the density of which is so limited. To anchor such Zn atoms onto other islands on Cu with high density is the key to enhancing the catalytic activity. To replace ZnO with Al 2 O 3 islands on Cu is not favored energetically. However, under reduction condition, Zn single atoms can stably decorate the edges of the Al 2 O 3 islands, resulting in the enhancement of the efficient active sites at the Cu/oxide interface. This could be the mechanism of the synergy effects taking place in the Cu/ZnO/Al 2 O 3 catalyst.