Energy Band Architecture of a Hierarchical ZnO/Au/CuO Nanoforest by Mimicking Natural Superhydrophobic Surfaces.

The ZnO/CuO heterojunction promises high efficiency in photocurrent conversion and other light-driven processes, but the lattice mismatch between ZnO and CuO leads to slow electron transfer and low conversion efficiency. In addition, the stability of CuO is still the main challenging and limiting factor for device applications in real environments. CuO is a mixed semiconductor of CuO and CuO, which is a promising alternative to CuO in device fabrication due to its better stability and photocatalytic efficiency. In this work, CuO nanorods were attached to vertically aligned gold-decorated ZnO nanorods, creating a hierarchical ZnO/Au/CuO nanoforest. In addition, the hierarchical surface shows superhydrophobicity, which can prevent CuO degradation by water and oxygen. Femtosecond time-resolved transient absorption spectroscopy was employed to investigate the electron transfer dynamics in the ZnO/Au/CuO heterojunction. The nanoforest demonstrates enhanced electron mobility, increased lattice match, and higher photocurrent conversion efficiency compared with bare ZnO, CuO, or ZnO/CuO.