Electron blocking and hole extraction by a dual-function layer for hematite with enhanced photoelectrocatalytic performance

Abstract

To address the poor charge transport performance and severe surface combination of Hematite (Fe2O3), surface modification of electron blocking layer with a more negative conduction band than Fe2O3 have gradually received attention, which could prevent excess electrons escaping from Fe2O3 to the electrode surface. However, the electron blocking process is often accompanied by the similar hole blocking effect, resulting in severe secondary interface recombination. Here, we design a ZnFe2O4 active layer between Fe2O3 substrate and ZnO electron blocking layer to avoid the interface stacking phenomenon of photogenerated carriers. The photogenerated holes can be promptly extracted from valence band of Fe2O3 to the photoanode surface and the electrons can be smoothly delivered from Fe2O3 and FTO, avoiding the carriers interface accumulation. The optimized Fe2O3/ZnFe2O4/ZnO achieved a significant enhancement in photocurrent of 0.805 mA/ cm2 at 1.23 V vs. RHE when compared to the pristine Fe2O3 value of 0.12 mA/ cm2, Fe2O3/ZnFe2O4 of 0.58 mA/ cm2 and Fe2O3/ZnO of 0.38 mA/ cm2, increased by 670%, 140% and 210%, respectively. Meanwhile, the degradation rate constant is remarkably increased by 483%, 144% and 191% for treating a typical organic pollutant of methyl orange. Our finding emphasizes the importance of electron blocking layer and holes extraction layer on overall photogenerated carriers’ transfer, in achieving a hematite based photoanode with high PEC performance. These results provide a new strategy toward the surface design of more efficient PEC water splitting and organic degradation photoanode.