High-Efficient Photoelectrochemical Water Splitting of the Three-Dimensional ZnO Nanostructure

In recent years, ZnO has attained focus in water splitting applications due to the benefits of low cost, ease of fabrication, and high chemical stability. Here, we proposed a three-dimensional (3D) inclined ZnO nanowire structure via an Au catalyst-assisted vapor-liquid-solid method. This ZnO nanostructure exhibited better photoelectrochemical performance as compared with the ordinary 1D ZnO nanowires because of the increased area for the light-receiving and catalyst reaction. Furthermore, the 3D ZnO structure was doped with nitrogen using a post-annealing process, the photocurrent density of the <i>N</i>-doping ZnO was significantly increased from 1.68 mA/cm² to 2.82 mA/cm² at 1.23 V vs. RHE, and the photon-to-current conversion efficiency at 400 nm wavelength reached 7.3%. The strategy of appropriate <i>N</i>-doping can effectively increase carrier concentration of samples, and the carrier concentration of the sample annealed for one hour reaches the maximum of 6.54×10¹⁸. In this study, the photoelectric properties of ZnO materials were considerably enhanced by constructing a 3D ZnO nanostructure and N doping.