Pulse electrodeposited amorphous tunnel layer stabilises Cu2O for efficient charge separation under visible-light irradiation
Surface coating of a protective layer can prevent the corrosion of Cu2O at electrode liquid junctions (ELJ) in photoelectrochemical applications. However, a facile methodology for the deposition of a conformal protective layer is still a challenge. Here, an ultrathin layer of amorphous ZnO is introduced on Cu2O by pulsed electrodeposition, to construct a “sandwich” structure of composite photoelectrode of TiO2/ZnO/Cu2O on FTO substrate. Time-of-flight secondary ion mass spectroscopy (ToF-SIMs) visualises the spatial distribution of Ti, Zn, Cu, and Sn elements of the composite. Benefiting from the homogeneous coating of a ZnO layer, visible cracks in TiO2 coatings are significantly reduced, thus preventing the direct contact between the electrolyte and the Cu2O. Moreover, due to the ultrathin property of amorphous ZnO layer, the energetic electrons from the excited Cu¬2O can be injected via the ZnO layer to TiO2, as elucidated by time-resolved photoluminescence (TRPL) results. The resulting composite photoelectrode shows enhanced photoelectrochemical activity and stability, compared to the bare Cu2O, as well as the TiO2/Cu2O photoelectrode. This study offers a versatile and effective method for improving the stability and charge separation efficiency of Cu2O, which is useful in guiding the surface coating of other nanostructured materials for solar energy conversion.