Facile Synthesis of FeOOH Quantum Dots Modified ZnO Nanorods Films via a Metal-Solating Process

In this study, we referenced the formation principle of rust in nature and the FeOOH quantum dots (QDs) were prepared using a metal-solating process. The FeOOH QDs exhibited an average diameter of 3.5 nm with well crystallinity. Furthermore, the as-prepared FeOOH QDs were deposited on ZnO nanorods film as a co-catalyst for water oxidation. The crystal phase, microstructures, and optical properties of the synthesized films were established through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and ultraviolet–visible absorption spectroscopy (UV-vis). Applied as a photoanode for solar water splitting, the FeOOH QDs/ZnO nanorods film exhibited a photocurrent density of 0.44 mA/cm² at 1.23 V vs RHE, which is 2.1 times higher than that of pure ZnO film. After the loading of FeOOH QDs, the ZnO photoanode showed higher surface charge injection efficiency (by a factor of ∼2) and better long-term stability. The analysis of electrochemical measurements displayed that, as a co-catalyst of the oxygen evolution reaction, FeOOH QDs resulted in a noticeable cathodic shift of photocurrent onset potential for water oxidation and a remarkable improvement of surface charge injection efficiency. In addition, the metal-solating method can be applied to preparing the other metal oxides QDs, such as WO₃ and ZnO QDs.