Abstract
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) O(3) catalysts subjected to a mixture of CO and O(2) 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 Mn(2+) to Mn(3+) and Mn(4+), while Co largely maintains a valence state of Co(2+). In the case of LaCoO(3), we identify high-spin and low-spin Co(3+) species combined with Co(2+). Our investigation underscores the importance to consider the spin and valence states of catalyst materials under operando conditions.