Department of Chemistry , Tsinghua University , Beijing 100084 , China.
School of Materials Science and Engineering , Beihang University , Beijing 100191 , China.
Environ Sci Technol. 2018 Aug 7;52(15):8684-8692. doi: 10.1021/acs.est.8b01594. Epub 2018 Jul 17.
α-MnO is a promising material for ozone catalytic decomposition and the oxygen vacancy is often regarded as the active site for ozone adsorption and decomposition. Here, α-MnO nanowire with tunable K concentration was prepared through a hydrothermal process in KOH solution. High concentration K in the tunnel can expand crystal cell and break the charge balance, leading to a lower average oxidation state (AOS) of Mn, which means abundant oxygen vacancy. DFT calculation has also proven that the samples with higher K concentration exhibit lower formation energy for oxygen vacancy. Due to the enormous active oxygen vacancies existing in the α-MnO nanowire, the lifetime of the catalyst (corresponding to 100% ozone removal rate, 25 °C) is increased from 3 to 15 h. The FT-IR results confirmed that the accumulation of intermediate oxygen species on the catalyst surface is the main reason why it is deactivated after long time reaction. In this work, the performance of the catalyst has been improved because the abundant active oxygen vacancies are fabricated by the electrostatic interaction between oxygen atoms inside the tunnels and the introduced K, which offers us a new perspective to design a high efficiency catalyst and may promote manganese oxide for practical ozone elimination.
α-MnO 是一种很有前途的臭氧催化分解材料，而氧空位通常被认为是臭氧吸附和分解的活性位。在这里，通过在 KOH 溶液中的水热过程制备了具有可调 K 浓度的 α-MnO 纳米线。隧道中高浓度的 K 可以扩展晶胞并打破电荷平衡，导致 Mn 的平均氧化态（AOS）较低，这意味着存在丰富的氧空位。DFT 计算也证明了具有较高 K 浓度的样品具有较低的氧空位形成能。由于 α-MnO 纳米线中存在大量的活性氧空位，催化剂的寿命（对应于 100%臭氧去除率，25°C）从 3 小时增加到 15 小时。FT-IR 结果证实，催化剂表面上中间氧物种的积累是其在长时间反应后失活的主要原因。在这项工作中，通过隧道内氧原子与引入的 K 之间的静电相互作用制造了丰富的活性氧空位，从而提高了催化剂的性能，这为我们设计高效催化剂提供了新的视角，并可能促进氧化锰在实际臭氧消除中的应用。
