Peanut-Shaped Cu–Mn Nano-Hollow Spinel with Oxygen Vacancies as Catalysts for Low-Temperature NO Reduction by CO
Yu Qin, Shiying Fan, Xinyong Li, Guoqiang Gan, Liang Wang, Zhifan Yin, Xuecheng Guo, Moses O. Tadé, Shaomin Liu
Abstract
Manganese–copper spinel is a kind of efficient catalyst for NO reduction by CO; however, its unsatisfactory low-temperature catalytic performance and poor N2 selectivity limit its application. Here, peanut-shaped Cu0.75Mn2.25O4 nano-hollow spinel (Cu0.75Mn2.25O4-NH) was prepared by a one-pot solvothermal method and applied in NO reduction by CO. The structure and physicochemical properties of catalysts were researched by comprehensive characterizations. Compared with Cu0.75Mn2.25O4 nanoparticles (Cu0.75Mn2.25O4-NP), Cu0.75Mn2.25O4-NH displayed excellent low-temperature catalytic performance, achieving 90% NO conversion at 200 °C, and possessed a lower apparent activation energy (36.4 kJ·mol–1). Importantly, the unique nanostructure with more exposed active sites enhanced the redox properties and oxygen mobility of the Cu0.75Mn2.25O4-NH catalyst. In addition, a synergistic effect between different metal ions in the Cu0.75Mn2.25O4-NH catalyst promoted the formation of oxygen vacancies and more low-oxidation-state species, which were conducive to the N–O bond scission at low temperatures. Combining the in situ DRIFTS results and DFT calculations, the dispersed species of Cuy+-O-Mnx+ could be reduced to the main reactive species of Cu(y–1)+-□-Mn(x–1)+. Moreover, the formation of oxygen vacancies optimized NO adsorption and activation ability, which improved the catalytic performance in NO reduction by CO.