Revealing the roles of surface treatments on hematite (α-Fe2O3) photoanode in the shift of the onset potential

Abstract

In this study, we fabricated different types of Hematite (α-Fe2O3)-based photoanodes, treated with CeOx, FeOOH, and NiFeOx, and investigated the effect of each treatment on the onset potential shift. We revealed the Hematite films that were treated with either CeOx or FeOOH on the surface did not exhibit cathodic shifts of the onset potentials in photocurrent density–potential (J–V) curves, in which the significant improvements in charge transfer efficiencies were achieved, while charge separation efficiencies were not significantly enhanced. It means that the enhanced charge transfer efficiency resulting from the catalyzed oxygen evolution reaction did not significantly influence the shift of the turn-on voltage. On the other hand, we were able to observe the significant improvement of the photo-electrochemical performance of Hematite treated with NiFeOx, including the cathodic shift of the onset potential, which could be attributed to the enhancement of the charge separation efficiency, resulting from the Fermi level unpinning. Based on the results, we could believe that the cathodic shift of the onset potential was primarily due to the enhancement of the photovoltage.