Enhanced performance of FeOOH/ZnIn2S4/Au nanosheet arrays for visible light water splitting

Carrier separation, charge transport, and visible light absorption are the main factors affecting the solar water splitting performance of a semiconductor photoanode. In this work, ZnIn2S4 (ZIS) nanosheet arrays (NSAs) were prepared by a hydrothermal route on a transparent fluorine-doped tin oxide (FTO) substrate, which was followed by a modification with an amorphous FeOOH thin layer. The surface morphology of ZIS NSAs was shown not to change regardless of whether Au was used as the seeding layer. Besides, the effect of the FeSO4 solution concentration on the morphology, optical absorption, and photoelectrochemical (PEC) performance was investigated. The PEC measurements showed that at the 1.23 V bias relative to RHE (VRHE), the FeOOH/ZIS/Au optical photoanodes exhibited a 4.5 and 1.9 times higher photocurrent density than the ZIS/FTO and ZIS/Au/FTO electrodes, respectively. For the 0.05Fe/ZIS/Au/FTO samples, the 0.91 mA cm−2 initial photocurrent density was achieved at VRHE of 1.23 V. The FeOOH/Au/ZIS photoanodes also displayed a maximum H2 yield amount of 26.2 µmol cm−2 h−1. It was also observed that the enhanced PEC performance may be resulted from the synergistic effect of the FeOOH top decoration and Au under layer. Specifically, FeOOH facilitated the hole injection into the electrolyte, while Au NPs provided a number of sinks for the electron transport to the FTO substrates.