From Methane to Methanol:\nPd-iC-CeO<sub>2</sub> Catalysts\nEngineered for High Selectivity via Mechanochemical Synthesis

In the pursuit of selective conversion of methane directly\nto methanol\nin the liquid-phase, a common challenge is the concurrent formation\nof undesirable liquid oxygenates or combustion byproducts. However,\nwe demonstrate that monometallic Pd-CeO<sub>2</sub> catalysts, modified\nby carbon, created by a simple mechanochemical synthesis method exhibit\n100% selectivity toward methanol at 75 °C, using hydrogen peroxide\nas oxidizing agent. The solvent free synthesis yields a distinctive\nPd-iC-CeO<sub>2</sub> interface, where interfacial carbon (iC) modulates\nmetal-oxide interactions and facilitates tandem methane activation\nand peroxide decomposition, thus resulting in an exclusive methanol\nselectivity of 100% with a yield of 117 μmol/g<sub>cat</sub> at 75 °C. Notably, solvent interactions of H<sub>2</sub>O<sub>2</sub> (aq) were found to be critical for methanol selectivity through\na density functional theory (DFT)-simulated Eley–Rideal-like\nmechanism. This mechanism uniquely enables the direct conversion of\nmethane into methanol via a solid–liquid–gas process.