Surficial engineering of active hydroxyls for ambient formaldehyde oxidation via enhanced Lewis acidity over Zr-doped cryptomelane materials

文献类型： 外文期刊

第一作者： Wang, Hui-Jun

作者： Wang, Hui-Jun;Yang, Huan-Huan;Chen, Tian-Yun;Zhan, Jingjing;Zhou, Hao;Yi, Xianliang;Zhang, Shi -Yu;Liu, Yang;Li, Zhonghong;Shen, Xudong

作者机构：

关键词： Air purification; Formaldehyde; Catalytic oxidation; Manganese oxide; Hydroxyl; Structure; Performance relation

期刊名称：ENVIRONMENTAL RESEARCH （ 影响因子：8.3； 五年影响因子：8.2 ）

ISSN： 0013-9351

年卷期： 2024 年 247 卷

页码：

收录情况： SCI

摘要： Lewis acids of solid catalysts have been featured for a pivotal role in promoting various reactions. Regarding the oxidation protocol to remove formaldehyde, the inherent drawback of the best-studied MnO2 materials in acidic sites has eventually caused deficiency of active hydroxyls to sustain low-temperature activity. Herein, the cryptomelane-type MnO2 was targeted and it was tuned via incorporation of Zr metal, exhibiting great advances in not only the complete HCHO-to-CO2 degradation but also cycling performance. Zr species were existent in doping state in the MnO2 lattice, rendering lower crystallinity and breaking the regular growth of MnO2 crystallites, which thereby tripled surface area and created larger volume of smaller mesopores. Meantime, the local electronic properties of Mn atoms were also changed by Zr doping, i.e., more low-valence Mn species were formed due to the electron transfer from Zr to Mn. The results of infrared studies demonstrate the higher possession of Lewis acid sites on ZrMn, and this high degree of electrophilic agents favored the production of hydroxyl species. Furthermore, the reactivity of surface hydroxyls, as investigated by CO temperature programmed reduction and temperature programmed desorption of adsorbed O2, was obviously improved as well after Zr modification. It is speculated jointly with the characterizations of the post-reaction catalysts that the accelerated production of active hydroxyls helped rapidly convert formaldehyde into key intermediate-formate, which was then degraded into CO2, avoiding the side reaction path with undesired intermediate-hydrocarbonate-over the pristine MnO2, where active sites were blocked and formaldehyde oxidation was inhibited. Additionally, Zr decoration could stabilize Lewis acidity to be more resistant to heat degeneration, and this merit brought about advantageous thermal recyclability for cycled application.

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