ABSTRACT
The ZnO/Cu2O heterojunction promises high efficiency in photocurrent conversion and other light-driven processes, but the lattice mismatch between ZnO and Cu2O leads to slow electron transfer and low conversion efficiency. In addition, the stability of Cu2O is still the main challenging and limiting factor for device applications in real environments. CuxO is a mixed semiconductor of CuO and Cu2O, which is a promising alternative to Cu2O in device fabrication due to its better stability and photocatalytic efficiency. In this work, CuxO nanorods were attached to vertically aligned gold-decorated ZnO nanorods, creating a hierarchical ZnO/Au/CuxO nanoforest. In addition, the hierarchical surface shows superhydrophobicity, which can prevent Cu2O degradation by water and oxygen. Femtosecond time-resolved transient absorption spectroscopy was employed to investigate the electron transfer dynamics in the ZnO/Au/CuxO heterojunction. The nanoforest demonstrates enhanced electron mobility, increased lattice match, and higher photocurrent conversion efficiency compared with bare ZnO, CuxO, or ZnO/CuxO.
ABSTRACT
Vertically aligned ZnO nanowire-based tree-like structures with CuO branches were synthesized on the basis of a multistep seed-mediated hydrothermal approach. The nanotrees form a p-n junction at the branch/stem interface that facilitates charge separation upon illumination. Photoelectrochemical measurements in different solvents show that ZnO/CuO hierarchical nanostructures have enhanced photocatalytic activity compared to that of the nonhierarchical structure of ZnO/CuO, pure ZnO, and pure CuO nanoparticles. The combination of ZnO and CuO in tree-like nanostructures provides opportunities for the design of photoelectrochemical sensors, photocatalytic synthesis, and solar energy conversion.
