Jin Chao, Si Wenzhe, Chen Ya, Zhao Xiaoguang, Zhou Bin, Shen Yu, Zhu Qiangqiang, Chu Yang, Liu Feng, Li Mingfeng, Li Junhua
Sinopec Research Institute of Petroleum Processing Co., Ltd, Beijing 100083, China.
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
J Colloid Interface Sci. 2024 Jun;663:541-553. doi: 10.1016/j.jcis.2024.02.051. Epub 2024 Feb 19.
The CO oxidation catalytic activity of catalysts is strongly influenced by the oxygen vacancy defects (OVDs) concentration and the valence state of active metal. Herein, a defect engineering approach was implemented to enhance the oxygen vacancy defects and to modify the valence of metal ions in manganese oxide octahedral molecular sieves (OMS-2) by the introduction of copper (Cu). The characterization and theoretical calculation results reveal that the incorporation of Cu ion into the OMS-2 structure led to a rise in specific surface area and pore volume, weakening of Mn-O bonds, higher proportion of the low-coordinated oxygen species adsorbed in oxygen vacancies (O) and an increase in the average oxidation state of manganese. These structural modifications were discovered to considerably reduce the apparent activation energy (Ea), thus ultimately significantly enhancing the CO oxidation activity (T at 148 ℃at GHSV = 13,200 h) than the original OMS-2 (T = 215 ℃ at GHSV = 13,200 h). Furthermore, In-situ diffuse reflectance infrared Fourier transform (DRIFT) and In-situ near-ambient pressure X-ray photoelectron spectroscopy (in situ NAP-XPS) results indicate that the bimetallic synergy enhanced by doping strategy accelerates the conversion of oxygen to chemisorbed oxygen species and the reaction rate of CO oxidation through Mn+Cu↔Mn+Cu redox cycle. The findings of this study offer novel perspectives on the design of catalysts with exceptional performance in CO oxidation.
催化剂的CO氧化催化活性受到氧空位缺陷（OVDs）浓度和活性金属价态的强烈影响。在此，通过引入铜（Cu）实施了一种缺陷工程方法，以增加氧空位缺陷并改变氧化锰八面体分子筛（OMS-2）中金属离子的价态。表征和理论计算结果表明，将Cu离子引入OMS-2结构导致比表面积和孔体积增加，Mn-O键减弱，吸附在氧空位（O）中的低配位氧物种比例更高，以及锰的平均氧化态增加。发现这些结构修饰显著降低了表观活化能（Ea），从而最终比原始OMS-2（在GHSV = 13,200 h时T = 215℃）显著提高了CO氧化活性（在GHSV = 13,200 h时T为148℃）。此外，原位漫反射红外傅里叶变换（DRIFT）和原位近常压X射线光电子能谱（原位NAP-XPS）结果表明，通过掺杂策略增强的双金属协同作用通过Mn+Cu↔Mn+Cu氧化还原循环加速了氧向化学吸附氧物种的转化以及CO氧化的反应速率。本研究结果为设计在CO氧化中具有优异性能的催化剂提供了新的视角。
