2026-05-17T07:08:45Z https://archive.materialscloud.org/oai2d

oai:materialscloud.org:16jd7-0zz18 2025-10-30T16:04:20Z openaire_data community-mcarchive

Li, Wen Shi, Junjie Tangpakonsab, Parinya Lewis Zhang, Bin Haunold, Thomas Genest, Alexander Yigit, Nevzat Atzl, Leonard Kokkonen, Esko Qin, Yong Rupprechter, Günther 2025-10-30 The direct conversion of methane to methanol (DCMM) under continuous flow and atmospheric pressure offers notable environmental benefits and industrial promise, but remains a long-standing challenge due to the difficulty of activating CH4 while avoiding over-oxidation of methanol. Here, we demonstrate that pure ceria (CeO2), without any metal promoters, enables gas-phase DCMM with up to 80 % selectivity at 300–350 °C, upon optimization of the H2O/O2 ratio. At 550 °C, methanol and formaldehyde are formed at rates of 24 and 36 μmol g-1 h-1, respectively-both dropping below 1 μmol g-1 h-1 in the absence of O2. Ex situ transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy confirm that CeO2 maintains structural integrity and resists carbon deposition during reaction. Combining kinetic studies, steady-state in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), and density functional theory (DFT) reveals that hydroxyl groups (OH), generated from water dissociation, play a multifaceted role: they facilitate C–H bond activation, promote methoxy formation, and enhance methanol desorption. In-situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) directly reveals the evolution of surface intermediates and shows that co-feeding O2 and H2O suppresses CH3O and CHx accumulation while boosting methanol yield—indicating a rapid intermediate turnover as key to sustained activity. AP-XPS O 1s spectra further highlight that O2 promotes H2O dissociation, regenerating reactive OH groups and maintaining performance at elevated temperature. These findings offer molecular-level insights into how water and oxygen cooperatively tune reactivity, enabling efficient methane-to-methanol conversion on a metal-free oxide catalyst. application/zip application/zip text/plain https://doi.org/10.24435/materialscloud:wn-rx oai:materialscloud.org:16jd7-0zz18 mcid:2025.171 eng Materials Cloud https://archive.materialscloud.org/communities/mcarchive https://doi.org/10.24435/materialscloud:3v-by info:eu-repo/semantics/openAccess Creative Commons Attribution 4.0 International https://creativecommons.org/licenses/by/4.0/legalcode CeO2 methane to methanol In-situ AP-XPS In-situ DRIFTS reaction mechanism DFT Synergy of oxygen and water in ceria-catalyzed direct conversion of methane to methanol under continuous flow info:eu-repo/semantics/other