Au-Modified Pd catalyst exhibits improved activity and stability for NO direct decomposition

Abstract

The direct decomposition of NOxat moderate temperatures is a challenge because of the poisoning of the surface of noble metals by oxygen, yet the modification of Pd with Au enables obtaining a highly stable catalyst under an O2-free feed at 450 °C. Care was taken to ensure that the reaction was not due to the reduction of NOxwith carbonaceous residues by monitoring CO2evolution. Pd-Au alloyed domains with a wide range of compositions were evidenced byin situandex situXRD, the Pd content of which decreased with the increasing oxidising nature of the feed due to phase segregation giving rise to PdO and an Au-rich alloy. Under air, the limiting alloy composition was Pd0.2Au0.8. The catalyst was yet inactive in the presence of 5% O2