The enhanced water splitting activity of a ZnO-based photoanode by modification with self-doped lanthanum ferrite

Abstract

The difficult separation and transfer of photoexcited charge carriers in composite photoelectrodes is a decisive factor limiting the efficiencies of semiconductor-based photoelectrochemical water splitting systems. Herein, to further enhance the photoelectrochemical properties of ZnO-based photoanodes, we constructed composite ZnO nanoarray photoanodes with Fe-self-doped lanthanum ferrite (denoted as La_1−xFe_1+xO₃/ZnO NRs), which had the effect of killing two birds with one stone. This improvement strategy differs from the previously popular multi-step modification process, and integrates the dual benefits of a heterojunction and cocatalyst using the same material, the doped LaFeO₃, which bypasses the shortcomings of multi-step charge transfer. Gratifyingly, benefitting from the suitable energy bands and excellent electrocatalytic oxygen evolution activity of La_0.9Fe_1.1O₃, the photoanode exhibits outstanding bulk charge separation and surface charge utilization efficiencies, as well as achieving a photocurrent density that is over three times higher than that of pristine ZnO NRs, with a small onset potential (0.33 V vs. RHE). This electrode modification concept provides guidance for the development of other highly active photoelectrodes.