A Probe into the Low-Temperature SCR Activity: NO Oxidative Activation to Nitrite-Intermediates

Investigation of the low-temperature (LT) selective catalytic reduction (SCR) of NOx has adsorbed extensive efforts, and is now a hot topic in environmental catalysis. In this work, we cautiously explore the mechanism beneath LT-SCR via a combination of chemical-trapping methods, using BaO/Al2O3 as a NOx-intermediate trap, temperature-programmed desorption (TPD) and in situ FTIR spectroscopy over a series of metal-oxide catalysts. Our results show a linear correlation between LT-SCR rates and amounts of nitrites generated from NO oxidative activation and sequentially stored on BaO/Al2O3, implying key roles of nitrites/nitrite-precursors in LT-SCR.