Hematite nanoarrays are important photoanode materials. However, they suffer from serious problems of charge transfer and surface states; in particular, the surface states hinder the increase in photocurrent. A previous strategy to suppress the surface state is the deposition of an Fe‐free metal oxide overlayer. Herein, from the viewpoint of atomic bonding energy, it is found that the strength of bonding around Fe atoms in the hematite is the key to suppressing the surface states. By treating the surface of hematite with Se and NaBH₄, the Fe₂O₃ transforms to a double‐layer nanostructure. In the outer layer, the Fe−O bonding is reinforced and the Fe−Se bonding is even stronger. Therefore, the surface states are inhibited and the increase in the photocurrent density becomes much faster. Besides, the treatment constructs a nanoscale p–n junction to promote the charge transfer. Improvements are achieved in onset potential (0.25 V shift) and in photocurrent density (5.8 times). This work pinpoints the key to suppressing the surface states and preparing a high‐efficiency hematite nanoarray, and deepens our understanding of hematite photoanodes.

中文翻译：

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高效的赤铁矿光电阳极，具有增强的铁原子键合能

赤铁矿纳米阵列是重要的光阳极材料。然而，它们遭受电荷转移和表面状态的严重问题。特别地，表面状态阻碍了光电流的增加。抑制表面状态的先前策略是沉积无铁的金属氧化物覆盖层。在此，从原子键合能的观点出发，发现赤铁矿中的Fe原子周围的键合强度是抑制表面状态的关键。通过用Se和NaBH ₄处理Fe ₂ O ₃赤铁矿表面转变为双层纳米结构。在外层中，Fe-O键得到增强，而Fe-Se键则更牢固。因此，表面状态被抑制并且光电流密度的增加变得更快。此外，该处理可构建一个纳米级的p–n结，以促进电荷转移。起始电位（0.25 V偏移）和光电流密度（5.8倍）得到了改善。这项工作指出了抑制表面状态和制备高效赤铁矿纳米阵列的关键，并加深了我们对赤铁矿光阳极的理解。