In fuel cells, the oxygen reduction reaction (ORR) at the cathode plays a crucial role in their performance. High cost, low abundance, catalyst poisoning, and poor durability of the pioneering ORR catalyst Pt make it less desirable for commercial fuel cells. Herein, we demonstrate a greener process to synthesize CeO₂ nanostructures by varying reaction parameters in a single-step solvothermal route and provide a detailed mechanism for the formation of CeO₂ nanostructures with different shapes. The shape and size of the CeO₂ nanostructures such as hollow/solid spheres, triangular flakes, nanotubes, and flower-like structures result in a strong effect on their ORR activity. A normalized effect of effective surface area and oxygen vacancies in CeO₂ nanostructures is found to govern the ORR activity order. Among the CeO₂ nanostructures, hollow spheres exhibit the best ORR activity with a four-electron reduction pathway. Moreover, they show comparable ORR activity and outstanding stability as well as methanol fuel tolerance and are a substitute for Pt/C.

中文翻译：

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使用无模板溶剂热法调节CeO2纳米结构的形态及其氧还原反应活性

在燃料电池中，阴极的氧还原反应（ORR）在其性能中起着至关重要的作用。开拓性的ORR催化剂Pt的高成本，低丰度，催化剂中毒以及较差的耐用性使得其对于商业燃料电池的需求降低。在这里，我们展示了一个绿色的过程，可以通过在一步溶剂热途径中改变反应参数来合成CeO ₂纳米结构，并为形成具有不同形状的CeO ₂纳米结构提供了详细的机理。CeO ₂纳米结构的形状和大小（例如空心/实心球，三角形薄片，纳米管和花状结构）对其ORR活性产生强烈影响。CeO ₂中有效表面积和氧空位的归一化效应发现纳米结构支配ORR活性顺序。在CeO ₂纳米结构中，空心球表现出最佳的ORR活性，并具有四电子还原途径。此外，它们显示出可比的ORR活性，出色的稳定性以及甲醇燃料耐受性，是Pt / C的替代品。