Cooperative effects of surface and interface treatments in a hematite (α-Fe2O3) photo-anode on its photo-electrochemical performance

Abstract

To enhance the efficiency of the oxygen evolution reaction of hematite (α-Fe₂O₃), we engineered both the surface of the hematite nanorods and the FTO/hematite interface simultaneously with an optimal annealing condition. We demonstrated that the enhancement of the photo-electrochemical performance of the hematite film treated by both methods was not just the summation of the improvements originating from each treatment but showed a significant cooperative effect. We clearly revealed that the strong electric field was effectively induced by the surface P doping with the concentration gradient profile, resulting in band bending even at 0 V vs. RHE. Furthermore, the dead layer was removed by the TiO₂ underlayer, giving rise to Fermi level unpinning. We confirmed that the introduction of the TiO₂ underlayer unpinning Fermi level enables building on the strength of the intrinsic long-lived holes generated by P doping, which is the origin of the cooperative effect.