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Methane is a valuable resource and its valorization is an important challenge in heterogeneous catalysis. Here it is shown that CeO 2 /CuO composite prepared by ball milling activates methane at a temperature as low as 250 °C. In contrast to conventionally prepared catalysts, the formation of partial oxidation products such as methanol and formaldehyde is also observed. Through an in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and operando Near Edge X-Ray Absorption Fine Structure Spectroscopy (NEXAFS) approach, it can be established that this unusual reactivity can be attributed to the presence of Ce 4+ /Cu + interfaces generated through a redox exchange between Ce 3+ and Cu 2+ atoms facilitated by the mechanical energy supplied during milling. DFT modeling of the electronic properties confirms the existence of a charge transfer mechanism. These results demonstrate the effectiveness and distinctiveness of the mechanical approach in creating unique and resilient interfaces thereby enabling the optimization and refining of CeO 2 /CuO catalysts in methane activation reactions., (© 2024 Wiley‐VCH GmbH.)

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., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)