Highly active and sintering-resistant heteroepitaxy of Au nanoparticles on ZnO nanowires for CO oxidation

Gold was supported on commercial ZnO powders (P) and homemade ZnO nanowires (NWs) by a modified deposition precipitation method. X-ray diffraction and transmission electron microscopy investigation indicated that the size of the Au nanoparticles (NPs) depended strongly on the calcination temperature. The Au NPs were highly dispersed (< 5 nm) on both supports with calcination temperatures < 400 degrees C. However, after calcination at 600 degrees C the Au NPs aggregated much more severely on ZnO P than on ZnO NWs. Gold NPs epitaxially grew into the {10-10} facets of the ZnO NWs after calcination at temperatures > 400 degrees C. Such unique anchoring mechanism accounts for the much better experimentally observed sintering resistance. X-ray photoelectron spectra showed that Au existed as both metallic Au-0 and Au delta+ species in all the synthesized catalysts with or without calcination treatment; the ratios of Au delta+/Au-0, however, varied, depending on the treatment conditions. Catalytic tests showed that the activity for CO oxidation strongly depended on the size of the Au NPs. After calcination at 600 degrees C, the specific rate for CO oxidation at room temperature decreased about 30 times on Au/ZnO P but only about 4 times on Au/ZnO NW. Stability tests demonstrated that the Au/ZnO NW catalysts had better stability for CO oxidation. (C) 2016 Science Press and Dalian Institute of Chemical Physics. All rights reserved.