ZnO-TiO₂ Core–Shell Nanowires: A Sustainable Photoanode for Enhanced Photoelectrochemical Water Splitting

Abstract

We present the synthesis of a unique vertically aligned ZnO-TiO2 core–shell nanowires (NWs) heterostructure on an Si-wafer using a chemical vapor deposition method. The structural study shows the well-developed ZnO-TiO2 core–shell NWs heterostructure. This unique ZnO-TiO2 core–shell NWs heterostructure displays a photocurrent density of 1.23 mA cm–2, which is 2.41 times higher than pristine ZnO NWs. A cathodic shift in the flat band potential and a lower onset potential of a ZnO-TiO2 core–shell NWs heterostructure over ZnO NWs indicates more favorable properties for photoelectrochemical water splitting with a photoconversion efficiencey of 0.53%. A higher photocurrent density/photoconversion efficiency is due to the effective addition of photogenerated electron–hole separation originating from the ZnO NWs core and the conformal covering of a amorphous TiO2 passivation shell. Therefore, these results suggest that the vertically aligned one-dimentional ZnO-TiO2 core–shell NWs heterostructure is a promising photoanode for solar energy conversion devices.