Operando Soft X-ray Absorption of LaMn_{1- x} Co _x O₃ 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_1-x Co _x O₃ catalysts subjected to a mixture of CO and O₂ 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 (x ≤ 0.5), Mn oxidizes from Mn²⁺ to Mn³⁺ and Mn⁴⁺, while Co largely maintains a valence state of Co²⁺. In the case of LaCoO₃, we identify high-spin and low-spin Co³⁺ species combined with Co²⁺. Our investigation underscores the importance to consider the spin and valence states of catalyst materials under operando conditions.