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

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.