Tan Zicong, Zhang Jieru, Chen Yu-Cheng, Chou Jyh-Pin, Peng Yung-Kang
Department of Chemistry, City University of Hong Kong, Hong Kong SAR, China.
Department of Mechanical Engineering, City University of Hong Kong, Hong Kong SAR, China.
J Phys Chem Lett. 2020 Jul 16;11(14):5390-5396. doi: 10.1021/acs.jpclett.0c01557. Epub 2020 Jun 24.
Although HO has been often employed as a green oxidant for many CeO-catalyzed reactions, the underlying principle of its activation by surface oxygen vacancy (V) is still elusive due to the irreversible removal of postgenerated V by water (or HO). The metastable V (ms-V) naturally preserved on pristine CeO surfaces was adopted herein for an in-depth study of their interplay with HO. Their well-defined local structures and chemical states were found facet-dependent affecting both the adsorption and subsequent activation of HO. It is concluded that a strong adsorption of HO on ms-V may not guarantee its subsequent activation. The ms-V 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 HO. This explains the 211.8 and 35.8 times enhancement in HO reactivity when the CeO surface is changed from (111) and (110) to (100).
尽管过氧化氢（HO）常被用作许多氧化铈（CeO）催化反应的绿色氧化剂，但由于水（或HO）会不可逆地去除生成后的氧空位（V），其通过表面氧空位（V）活化的潜在原理仍不清楚。本文采用天然保留在原始CeO表面的亚稳态V（ms-V）来深入研究它们与HO的相互作用。发现它们明确的局部结构和化学状态与晶面有关，这会影响HO的吸附及随后的活化。得出的结论是，HO在ms-V上的强吸附可能无法保证其随后的活化。只有当表面Ce的电子密度足够高以还原/断裂吸附的HO的O-O键时，ms-V才能在下一个催化循环中保持自由状态。这解释了当CeO表面从（111）和（110）变为（100）时，HO反应活性提高211.8倍和35.8倍的原因。
