Novel Core–Shell (ε-MnO₂/CeO₂)@CeO₂ Composite Catalyst with a Synergistic Effect for Efficient Formaldehyde Oxidation
2020
Zhang, Shuai | Wang, Haozhe | Si, Huayan | Jia, Xiaoqian | Wang, Ziyan | Li, Qiang | Kong, Jing | Zhang, Jianbin
A novel core–shell (ε-MnO₂/CeO₂)@CeO₂ composite catalyst with a synergistic effect was prepared by hydrothermal reaction and thermal decomposition and its application to high-efficiency oxidation removal of formaldehyde (HCHO) was systemically investigated. The (MnCO₃/CeO₂)@CeO₂ precursor was prepared first by the one-pot hydrothermal reaction of Mn²⁺ and Ce³⁺ solutions with a CO₂-storage material (CO₂SM) without any external templates or surfactants required. The thermal decomposition of the precursor afforded the core–shell (ε-MnO₂/CeO₂)@CeO₂ composite catalyst with excellent catalytic performance. HCHO in the feed gas (180 ppm HCHO, 21% O₂, N₂ balanced) at a gas hourly space velocity of 100 L/(gcₐₜ h) is 100% converted over the catalyst at 80 °C. The conversion rate remains above 95% in 72 h and above 73.8% in 140 h, suggesting the strong stability of the catalyst at high gas flow rates and relatively low temperatures. The synergistic mechanism of the catalyst was explored by X-ray diffraction, Raman, Brunauer–Emmett–Teller, transmission electron microscopy, and X-ray photoelectron spectroscopy. The number of defects in the catalyst and the strength of the Mn–O bond in ε-MnO₂ can be tuned by adjusting the synthesis conditions. More oxygen vacancies on the surface of CeO₂ can make the synergistic effect of the catalyst stronger, which significantly improves the lattice oxygen (Oₗₐₜₜ) activity on the surface of ε-MnO₂. Our work has provided new insights into the preparation of the desired composite catalysts with excellent performances.
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