The catalytic activity of CuZn catalysts in the synthesis of methanol was related to those reduced Cu species which originated from the CuxZn1-xO solid solution of wurtzite-like structure. Copper cations in the CuxZn1-xO solid solution were localized in the extended stacking faults of the ZnO lattice. Copper sites could supposedly be described as the product of introducing (OH)…Cu…(OH) to the planar defects of zinc oxide structure. Hydroxyl groups stabilize the planar defects of ZnO. The process of the samples reduction led to the formation of flat Cu0 particles over the surface of zinc oxide. The planar defects of ZnO structure were preserved in the reduced state. During the re-oxidation, Cu atoms returned to the extended stacking faults of ZnO as tape-like clusters of flat-square coordinated Cu cations.

Planar Defect of the Nanostructured Zinc Oxide as the Site for Stabilization of the Copper Active Species in Cu/ZnO Catalysts. Khassin, A.A., Pelipenko, V.V., Minyukova, T.P., Zaikovskii, V.I., Kochubey, D.I., Yurieva, T.M.: Catalysis Today, 2006, 112[1-4], 143-7