Low-Temperature Reduction of NO_x by NH₃ with Unity Conversion on Nanofilament MnO₂/Activated Semi-Coke Catalyst

Selective catalytic reduction of nitrogen oxides with NH₃ at low temperatures remains a crucial goal for industrial applications. However, effective catalysts operating at 70–90 °C are rarely reported, limiting SCR scenarios to high-temperature conditions. Herein, we report a unique MnO₂ nanofilament catalyst grown on activated semi-coke synthesized via a one-step in situ hydrothermal approach, which exhibits a stable and marked 100 % conversion rate of NO to N₂ with 100 % selectivity at 90 °C, superior to the other prepared structures (nanowires, nanorods, and nanotubes). Temperature-programmed desorption shows a large number of acid sites on MnO₂(NFs)/ASC, benefiting the formation of NH₄⁺ ions. Meanwhile, diffuse reflectance infrared Fourier transform spectroscopy reveals the activation of NO with O₂ to form bidentate nitrate/bridging nitrate NO₂ intermediates via bidentate nitrate species, triggering the Fast SCR with NH₃ at low temperatures. Such an effective, easy-to-prepare, and low-cost catalyst paves a new pathway for low-temperature SCR for a wide range of application scenarios.