Investigation of the modes of NO adsorption in Pd/H-CHA

This study investigates NO adsorption on Pd-exchanged chabazite (Pd/H-CHA), a promising passive NOx adsorber (PNA) for capturing cold-start emissions of gasoline- and diesel-powered vehicles. Temperature-programed desorption (TPD) IR spectroscopy are combined with theoretical calculations to elucidate how where is stored, water O2 affect this process. Pd/H-CHA produces two TPD features, around 423 753 K, bands centered at 1860 1810 cm−1. Calculated stretching frequencies maximum-desorption temperatures reveal that Pd2+ Pd+ sites responsible these low- high-temperature respectively, while the feature cm−1 due Pd+, contains contributions from both weakly-bound more strongly bound consistent experimentally observed effects O2.