Although H₂O₂ has been often employed as a green oxidant for many CeO₂-catalyzed reactions, the underlying principle of its activation by surface oxygen vacancy (V_o) is still elusive due to the irreversible removal of postgenerated V_o by water (or H₂O₂). The metastable V_o (ms-V_o) naturally preserved on pristine CeO₂ surfaces was adopted herein for an in-depth study of their interplay with H₂O₂. Their well-defined local structures and chemical states were found facet-dependent affecting both the adsorption and subsequent activation of H₂O₂. It is concluded that a strong adsorption of H₂O₂ on ms-V_o may not guarantee its subsequent activation. The ms-V_o can be only free for the next catalytic cycle when the electron density of surface Ce is high enough to reduce/break the O–O bond of adsorbed H₂O₂. This explains the 211.8 and 35.8 times enhancement in H₂O₂ reactivity when the CeO₂ surface is changed from (111) and (110) to (100).

中文翻译：

---

阐明结构良好的氧空位的结构几何形状和化学状态在原始CeO2上对H2O2活化的作用。

尽管H ₂ O ₂在许多CeO ₂催化的反应中经常被用作绿色氧化剂，但由于水不可逆地去除后生成的V _o，其通过表面氧空位（V _o）活化的基本原理仍然难以捉摸（或H ₂ O ₂）。本文采用天然保留在原始CeO ₂表面上的亚稳态V _o（ms-V _o）来深入研究它们与H ₂ O ₂的相互作用。发现它们的明确定义的局部结构和化学状态取决于刻面，从而影响H ₂ O ₂的吸附和随后的活化。结论是H ₂ O ₂在ms-V _o上的强吸附可能无法保证其随后的活化。当表面Ce的电子密度高到足以降低/破坏吸附的H ₂ O ₂的O-O键时，ms-V _o才可以在下一个催化循环中释放。这解释了当CeO ₂表面从（111）和（110）变为（100）时，H ₂ O ₂反应性提高了211.8和35.8倍。