Operando Soft X-ray Absorption of LaMn Co O Perovskites for CO Oxidation.

We employed operando soft X-ray absorption spectroscopy (XAS) to monitor the changes in the valence states and spin properties of LaMn Co O catalysts subjected to a mixture of CO and O at ambient pressure. Guided by simulations based on charge transfer multiplet theory, we quantitatively analyze the Mn and Co 2p XAS as well as the oxygen K-edge XAS spectra during the reaction process. The Mn sites are particularly sensitive to the catalytic reaction, displaying dynamics in their oxidation state. When Co doping is introduced ( ≤ 0.5), Mn oxidizes from Mn to Mn and Mn, while Co largely maintains a valence state of Co. In the case of LaCoO, we identify high-spin and low-spin Co species combined with Co. Our investigation underscores the importance to consider the spin and valence states of catalyst materials under operando conditions.