Abstract Transition metal oxide nanomaterials have been extensively applied to the field of oxygen evolution reaction (OER), but few works have been studied to demonstrate the relationship between their crystal phases and OER performance. Herein, we compare the OER performance of the two different crystal phase iron oxide (α-Fe2O3 and γ-Fe2O3). The iron oxide yolk-shell microspheres were facile realized via one-step solvothermal method and the subsequent annealing treatment. An interesting phenomenon is present that α-Fe2O3 yolk-shell microspheres with a smaller specific surface area have better OER performance than that of γ-Fe2O3 yolk-shell microspheres. The crystal structure and X-ray photoelectron spectroscopy (XPS) results show that α-Fe2O3 yolk-shell microspheres have better electrocatalytic activity, which is due to the presence of more Fe active sites (Fe3+) exposured on the surface. These Fe active sites are beneficial to enhance the adsorption of hydroxyl groups in water molecules, leading to a higher OER performance. As an application example, the Fe2O3 yolk-shell microspheres are employed as an efficient OER electrocatalyst, showing the interdependence between phase and OER behavior.

中文翻译：

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晶相确定 Fe2O3（γ-和 α-Fe2O3）蛋黄壳微球上的 Fe 活性位点及其相依赖性电催化析氧反应

摘要 过渡金属氧化物纳米材料已广泛应用于析氧反应（OER）领域，但很少有人研究证明其晶相与OER性能之间的关系。在此，我们比较了两种不同晶相氧化铁（α-Fe2O3 和 γ-Fe2O3）的 OER 性能。通过一步溶剂热法和随后的退火处理，可以很容易地实现氧化铁蛋黄壳微球。一个有趣的现象是比表面积较小的α-Fe2O3蛋黄壳微球比γ-Fe2O3蛋黄壳微球具有更好的OER性能。晶体结构和X射线光电子能谱（XPS）结果表明α-Fe2O3蛋黄壳微球具有较好的电催化活性，这是由于存在更多暴露在表面上的 Fe 活性位点 (Fe3+)。这些Fe活性位点有利于增强水分子中羟基的吸附，从而获得更高的OER性能。作为一个应用实例，Fe2O3 蛋黄-壳微球被用作一种高效的 OER 电催化剂，显示出相和 OER 行为之间的相互依赖性。