A new strategy for the surface-free-energy-distribution induced selective growth and controlled formation of Cu2O-Au hierarchical heterostructures with a series of morphological evolutions

A strategy of surface-free-energy-distribution induced selective growth of Au nanograins (AuNGs) on specific positions of Cu2O octahedron surfaces with a series of morphological evolutions has been demonstrated. The surface energy distribution of Cu2O octahedra generally follows the order of {111} facets < crystal edges < vertices and leads to the preferential growth and evolution of the heterostructures. The morphological evolutions and crystal structures of Cu2O and Cu2O-Au hierarchical heterostructures are investigated and discussed. Meanwhile, Cu2O octahedra coated by different amounts of polyvinyl pyrrolidone (PVP) and HAuCl4 were taken as control and the results indicate that the trend in the selective growth on PVP coated Cu2O octahedra decreased significantly because of the reducing diversity of the surface-free-energy-distribution. The identity and crystal phase structures of these Cu2O, Cu2O-Au and Cu2O-PVP-Au heterostructures are manifested through X-ray diffraction (XRD) and energy-dispersive X-ray spectrometers (EDS). X-ray photoelectron spectroscopy (XPS) further probes the surface chemical compositions and chemical oxidation state of the as-prepared Cu2O and Cu2O-Au hierarchical heterostructures and test the galvanic reaction between Cu2O and AuCl4-. The growth mechanism of the surface-free-energy-distribution induced selective growth of AuNGs on Cu2O octahedra with morphological evolution is also discussed. The photocatalytic performances of the as-prepared Cu2O and Cu2O-Au hierarchical heterostructures for the degradation of methyl orange (MO) are investigated and the results suggest the substantially enhanced photocatalytic activity of these heterostructures.