Thin-Layer Fe₂TiO₅ on Hematite for Efficient Solar Water Oxidation

A thin Fe₂TiO₅ layer was produced on hematite either by evaporating a TiCl₄ solution on FeOOH or by a simple HF-assisted Ti treatment of FeOOH, both followed by annealing. The prepared Fe₂TiO₅-hematite heterostructure showed a significant enhancement in photocurrent density compared to that of the pristine hematite. For example, the sample after HF-assisted Ti treatment exhibited a significantly enhanced photocurrent of 2.0 mA/cm² at 1.23 V <i>vs</i> RHE. Moreover, the performance of the Fe₂TiO₅-hematite heterostructure can be further improved by coupling with Co-Pi catalysts, achieving a higher photocurrent of 2.6 mA/cm² at 1.23 V <i>vs</i> RHE. Synchrotron-based soft X-ray absorption spectroscopy analyses clearly revealed the existence of an Fe₂TiO₅ structure on hematite forming a heterojunction, which reduced the photogenerated hole accumulation and then improved the performance