Degradation of Formaldehyde over MnO/CeO Hollow Spheres: Elucidating the Influence of Carbon Sphere Self-Sacrificing Templates.

Here, we prepare a MnO/CeO hollow sphere catalyst using the carbon sphere as a self-sacrificing template for formaldehyde (HCHO) removal. In the feed gas of 20 ppm of HCHO (balanced by N) + 20 vol % O, a HCHO removal efficiency of 70% was achieved at 20 °C and full conversion was reached at around 47 °C at GHSV = 50,000 mL (g h) for MnO/CeO hollow spheres. The catalytic performance and structural and chemical properties of MnO/CeO hollow spheres for the removal of core carbon spheres were explored, and the influence of using the carbon sphere as a self-sacrificing template was proved by comparing with carbon@MnO/CeO (a core carbon sphere with a MnO/CeO shell) and nonmorphologic MnO/CeO. The properties of the MnO/CeO hollow spheres are significantly improved compared to carbon@MnO/CeO (removal efficiency of 45% at 150 °C) and MnO/CeO (removal efficiency of 46% at 20 °C) as a result of an evolution in the interaction between Mn/Ce and carbon. This increase in the interaction strength seems to (i) increase the oxygen vacancy, (ii) promote the oxygen species mobility, and (iii) improve the chemical stability of the MnO/CeO hollow spheres. We believe that these results are beneficial to the fabrication of binary transition metal oxides and applications of them in HCHO removal.