Abstract: Catalytic reduction of NO_x with NH₃ was studied over MnO_x coated TiO₂ nanotube arrays prepared by anodic oxidation. When the MnO_x was deposited inside the TiO₂ nanotubes, the good NO_x removal efficiency was achieved under relatively low reaction temperature, such that NO_x removal efficiency of over 90% was always obtained at 150–250 °C, particularly at 200 °C, it reached 99.9%. However, when the reaction temperature was higher than 250 °C, a suppression of NO_x removal was observed. This is probably because that the diffusion of NO molecules into TiO₂ nanotubes was controlled by Knudson diffusion.

Key words: manganese oxide, titanium dioxide nanotube array, nitrogen oxide, selective catalytic reduction