Controllable synthesis of Ce-doped α-MnO2 for low-temperature selective catalytic reduction of NO

Abstract

The activity for selective catalytic reduction (SCR) of NO is related to the LUMO energy level of Mn atoms exposed on the surface of MnO₂ crystals. Our density functional theory (DFT) study reveals that α-MnO₂ has higher catalytic activity than β-MnO₂ for SCR of NO at relatively low temperature. By using SBA-15 as a template, Ce-doped α-MnO₂ (MnCe(0.3)O_x) with an ordered porous structure and high surface area (313 m² g⁻¹) was synthesized. Transmission electron microscopy, powder X-ray diffraction and Raman spectroscopy were employed to characterize the crystal structure of the α-MnO₂ catalyst. The SCR of NO in the presence of NH₃ using the MnCe(0.3)O_x catalyst was carried out at relatively low temperature. The NO conversion can approach 100% at 120 °C under a gas hourly space velocity (GHSV) of 160 000 h⁻¹ and at 170 °C under a GHSV of 500 000 h⁻¹. Thus, the present MnCe(0.3)O_x catalyst is expected to overcome the bottlenecks of high energy consumption and short usage age of catalysts in the SCR of NO.