To improve the photoelectrochemical (PEC) performance of hematite thin-film photoanode, we report a novel heterostructure based on Fe₂O₃/TiO₂ and hydrogenated Fe₂O₃/TiO₂ (Fe₂O₃/H:TiO₂) for faster charge transfer owing to passivation of surface states in Fe₂O₃ via TiO₂ overlayer and favorable band alignment using hydrogen annealing of TiO₂ overlayer. The valence band offset, band gap and work function values have been measured using X-ray photoelectron spectroscopy, optical absorption, and Kelvin probe force microscopy to construct the energy band diagram of the heterostructure photoanodes. The results confirm the upshift in the valence band edge of TiO₂ over Fe₂O₃ after hydrogen treatment of TiO₂ overlayer, which leads to the formation of type II band edge alignment in Fe₂O₃/H:TiO₂ heterojunction and improved PEC performance compared to Fe₂O₃/TiO₂, pristine Fe₂O₃ and TiO₂ thin-film photoelectrodes. The well-straddled and improved band alignment in Fe₂O₃/H:TiO₂ heterostructure gives rise to substantial enhancement in photocurrent density, up to 3.36 mA/cm² at 1.23 V (vs reversible hydrogen electrode (RHE)) with a low onset potential of 0.1 V (vs RHE), under AM1.5 illumination condition. The observed photocurrent density in Fe₂O₃/H:TiO₂ heterostructure is 15-fold higher than bare Fe₂O₃ (0.22 mA/cm²) photoanode. This work shows how a simple bilayer junction and its hydrogen treatment can be used to enhance the PEC response of heterojunctions and offers valuable insights into the further development of all-oxide heterojunctions.

中文翻译：

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所有氧化物的α-Fe ₂ ö ₃ / H：的TiO ₂异质结光阳极：一个平台，稳定和增强型光电化学性能通过有利带边缘对齐

为了提高赤铁矿薄膜光电阳极的光电化学性能，我们报道了一种基于Fe ₂ O ₃ / TiO ₂和氢化的Fe ₂ O ₃ / TiO ₂（Fe ₂ O ₃ / H：TiO ₂）的新型异质结构。由于通过TiO ₂覆盖层使Fe ₂ O _3中的表面态钝化，以及使用TiO ₂进行氢退火而实现了良好的能带取向，因此电荷转移更快覆盖层。价带偏移，带隙和功函数值已使用X射线光电子能谱，光学吸收和开尔文探针力显微镜进行了测量，以构建异质结构光阳极的能带图。该结果证实了在对TiO ₂覆层进行氢处理之后，TiO ₂的价带边缘在Fe ₂ O ₃之上的上移，这导致在Fe ₂ O ₃ / H：TiO ₂异质结中形成II型带边缘排列并得到改善。与Fe ₂ O ₃ / TiO ₂，原始Fe ₂ O ₃相比的PEC性能和TiO ₂薄膜光电极。Fe ₂ O ₃ / H：TiO ₂异质结构中跨度良好并能改善的能带排列可显着提高光电流密度，在1.23 V（vs可逆氢电极（RHE））下，电流密度低至3.36 mA / cm ²在AM1.5照明条件下的起始电势为0.1 V（vs RHE）。Fe ₂ O ₃ / H：TiO ₂异质结构中观察到的光电流密度比裸Fe ₂ O ₃（0.22 mA / cm ²）光电阳极。这项工作显示了如何使用简单的双层结及其氢处理来增强异质结的PEC响应，并为进一步发展全氧化物异质结提供了宝贵的见识。