Hollow MnO_x-CeO₂ nanospheres prepared by a green route: A novel low-temperature NH₃-SCR catalyst

A series of manganese-cerium oxide (MnO_x-CeO₂) catalysts were successfully prepared by supercritical antisolvent process and used for low temperature selective catalytic reduction (SCR) of NOx with NH ₃. The physicochemical properties of the catalysts were studied by using high-resolution transmission electron microscope, N2 adsorption, X-ray diffraction, X-ray photoelectron spectra, Raman spectra and temperature programmed reduction etc. Hollow spherical morphologies, nanocrystalline structures and solid solution structures were detected for these catalysts. The most active hollow nanospheres were obtained with a molar Mn/(Mn?Ce) ratio of 0.32 and a calcination temperature of 500 °C. Higher surface area, better oxygen mobility and richer surface active oxygen species are responsible for the good performance. The hollow MnO_x- CeO₂ nanospheres can be a new alternative for the lowtemperature SCR catalysts.