The broad O 1s peak in Figure 4(c) was comprised of two small peaks, one is located at 530.508???eV and the other one is located at 532.265???eV. The former is inherent O atoms bound to metals such as Cu and Zn, while the latter peak resulted from the possible surface contaminations by hydroxyl species and carbonate species [34].Table 1: Binding energies (eV), fwhm of the hierarchical CuO/ZnO nano