Electrochemical deposition synthesis of ZnO-NA/Cu2O-NPs type-II hierarchical heterojunction for enhanced photoelectrochemical degradation of methyl orange (MO)

Highly ordered ZnO nanorods array (ZnO-NA) films were fabricated on fluorine-doped tin oxide (FTO) substrates via a facilitate one-step electrochemical deposition route. Cu2O nanoparticles (Cu2O-NPs) films were then electrochemical deposited on the surface of ZnO-NA to constituted the ZnO-NA/Cu2O-NPs type-II hierarchical heterojunction. Steady-state photoluminescence (PL) spectra and nanosecond time-resolved transient photoluminescence (NTRT-PL) spectra of as-fabricated nanocomposites are studied, under light irradiation with wavelength of 266 nm. Simultaneously, a distinct 520 nm transient PL emission peak in the NTRT-PL spectra is observed owing to the presence of oxygen vacancy (OV) defect states, which is further convinced by the X-ray photoelectron spectroscopy (XPS). The PL decay spectroscopy confirms that ZnO-NA/Cu2O-NPs heterojunction could implement more facilitated avenue for transform and separation of photogenerated carriers associated with OV. Besides, the synthesized ZnO-NA/Cu2O-NPs nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectrophotometer, Raman scattering spectra and linear sweep voltammogram (LSV) measurement, respectively. Our present research demonstrates a new approach to investigate charge separation and transport in a dual-band gap photoelectrochemical (PEC) system. Following this scheme, UV and visible-light photocatalytic activities of ZnO-NA/Cu2O-NPs heterojunction nanocomposites were evaluated through photodegradation of methyl orange (MO) in aqueous solution.