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.

Core–Shell Photoanodes for Photoelectrochemical Water Oxidation

“…[ 112 ] Jeong et al. [ 92 ] employed CVD to create a TiO 2 shell on ZnO nanorod array using titanium tetraisopropoxide as precursor. The use of a single precursor guaranteed the homogeneity of the layer because the stoichiometry is defined by the precursor.…”

“…Reproduced with permission. [ 92 ] Copyright 2018, American Chemical Society. d) TEM image of core–shell ZnO@ZnGa 2 O 4 .…”

Synthesis of Nano-ZnO/Diatomite Composite and Research on Photoelectric Application

“…The obtained fast light response and chemical stability can be attributed to the loading of ZnO, generating Zn-O-Si bonds, which allows photoraw electrons to separate quickly and efficiently. Figure 13d shows the efficiency diagrams of composites with various loading ratios for water electrolysis, where it is clear that the efficiency of the catalyst after loading is greater than that of pure ZnO nanoparticles, indicating that the Si-O-Zn bonds are conducive to the transmission of electrons and improve the efficiency of water electrolysis [31].…”

A High-Efficiency TiO2/ZnO Nano-Film with Surface Oxygen Vacancies for Dye Degradation

“…To accelerate electron transport and reduce charge recombination of TiO 2 , many ways have been designed and employed, such as doping with transition metal or non-metal [8], increasing surface area [9], and constructing a proper heterostructure [10], etc. Among these different methods, constructing a proper heterostructure is one of the most effective strategies to improve the photocatalytic ability of TiO 2 by accelerating the transfer of photo-generated e-h pairs at the interface between various semiconductor materials [11][12][13]. Zinc oxide (ZnO), as an excellent n-type semiconductor material, has been demonstrated as a preferred material to couple with TiO 2 due to its facile synthesis, high photocatalytic efficiency, high abundance, and the fact that energy band position with ZnO is marginally more negative than that in TiO 2 [14].…”