The photoelectrochemical properties of polycrystalline GaFeO₃ (GFO) thin films are investigated for the first time. Thin films prepared by sol–gel methods exhibit phase‐pure orthorhombic GFO with the Pc21n space group, as confirmed by X‐ray diffraction and Raman spectroscopy. Optical responses are characterized by a 2.72 eV interband transition and sub‐bandgap d–d transitions associated with octahedral and tetrahedral coordination of Fe³⁺ sites. DFT‐HSE06 electronic structure calculations show GFO is highly ionic with very low dispersion in the valence band maximum (VBM) and conduction band minimum (CBM). Electrochemical impedance spectroscopy reveals n‐type conductivity with a flat band potential (U_fb) of 0.52 V versus reversible hydrogen electrode, indicating that GFO has the most positive CBM reported of any ferrite. The photoelectrochemical oxidation of SO₃²⁻ shows an ideal semiconductor–electrolyte interfacial behavior with no evidence of surface recombination down to the U_fb. Surprisingly, the onset potential for the oxygen evolution reaction also coincides with the U_fb, showing interfacial hole‐transfer efficiency above 50%. The photoelectrochemical properties are limited by bulk recombination due to the short‐diffusion length of minority carriers as well as slow transport of majority carriers. Strategies towards developing high‐efficiency GFO photoanodes are briefly discussed.

中文翻译：

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GaFeO3薄膜光阳极上的高界面空穴传输效率

首次研究了多晶GaFeO ₃（GFO）薄膜的光电化学性能。X射线衍射和拉曼光谱证实，通过溶胶-凝胶法制备的薄膜表现出具有Pc 21 n空间群的纯相正交晶GFO 。光学响应的​​特征是与Fe ³⁺位点的八面体和四面体配位相关的2.72 eV带内跃迁和亚带隙d–d跃迁。DFT-HSE06电子结构计算表明，GFO是高度离子化的，在价带最大值（VBM）和导带最小值（CBM）中的色散非常低。电化学阻抗谱显示具有平坦带电势的U型电导率（U _fb）相对于可逆氢电极为0.52 V），表明GFO在所有铁氧体中具有最正的CBM报道。SO ₃ ^2-的光电化学氧化显示出理想的半导体-电解质界面行为，没有证据表明表面重组到U _fb。令人惊讶的是，氧气逸出反应的起始电位也与U _fb一致，表明界面空穴转移效率超过50％。由于少数载流子的扩散长度短以及多数载流子的传输速度慢，因此光电化学性质受到本体复合的限制。简要讨论了开发高效GFO光阳极的策略。