Construction of ZnO/CdS three-dimensional hierarchical photoelectrode for improved photoelectrochemical performance

Three-dimensional ZnO/CdS hierarchical films with uniform CdS deposition on the ZnO nanorods surface is prepared by a two-step hydrothermal method. The morphology of CdS nanostructure can be adjusted from particles to sheets and then blocks by changing amount of the surfactant in the precursor solution. The ZnO/CdS hierarchical film as photoelectrode with optimized morphology shows significant enhancement to the light harvesting and photoelectrochemical performance. Under light irradiation of 100 mW/cm², the three-dimensional ZnO/CdS hierarchical film yields a photocurrent density of 4.5 mA/cm², approximately two times higher than that of film without three-dimensional structure. The photoelectrochemical property improvement is attributed to the (1) enhanced light absorption due to the multi-scattering and multi-reflection of the unique three-dimensional hierarchical structure, (2) improved photogenerated carrier separation and transportation because of the hierarchical and heterojunction structure, and (3) facilitated hole transfer and reaction at the photoelectrode-electrolyte interface due to the large surface area.