IR spectroscopy has been extensively employed to characterize the structural and vibrational properties of carbonates; yet, its application in studying the adsorption capacity of carbonate surfaces remains limited.

A large signal of gas-phase CO overlapping with those of adsorbates is often present when investigating catalysts by operando diffuse reflectance FT-IR spectroscopy. Physically removing CO(g) from the IR cell may lead to a fast decay of adsorbate signals. Our work shows that carbonyls adsorbed on metallic Pt sites fully vanished in less than 10 min at 30 °C upon removing CO(g) when redox supports were used. In contrast, a broad band assigned to CO adsorbed on oxidized Pt sites was stable. It was concluded that physically removing CO(g) at room temperature during IR analyses will most likely lead to changes in the distribution of CO(ads) and a misrepresentation of the Pt site speciation, misguiding the development of efficient low-temperature CO oxidation catalysts. A tentative representation of the nature of the Pt phases present depending on the feed composition is also proposed.

The direct decomposition of NO_x at 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 NO_x with carbonaceous residues by monitoring CO₂ evolution. Pd–Au alloyed domains with a wide range of compositions were evidenced by in situ and ex situ XRD, 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 Pd_0.2Au_0.8. The catalyst was yet inactive in the presence of 5% O₂.