Oxygen-Activated Dual-Atom Catalysts on Graphene for Direct Oxidation of Methane to Methanol: A DFT Study

The direct oxidation of methane (CH4) to methanol (CH3OH) with molecular oxygen (O2) as a green oxidant remains a formidable challenge, primarily due to the high energy barriers for the cleavage of the O–O bond and CH3–H bond activation. Here, we demonstrate that graphene-based dual-atom catalysts (TM1Zn-NPG, TM1 = Ti/V/Cr/Mn/Fe/Co/Ni/Cu) exhibit exceptional potential for this reaction. Through systematic density functional theory (DFT) calculations, FeZn-NPG is identified as the optimal catalyst, achieving a remarkably low energy barrier of 0.93 eV for the rate-limiting step (O2–O*–CH4 → O2–OH*–CH3•). Mechanistic studies reveal that O2 coadsorption on the FeZn-NPG-O* surface dynamically modulates the electronic structure of Fe sites, enabling their dual function as an electron reservoir to facilitate CH3–H bond activation (0.15 eV for O2*–CH4 → O–OH*–CH3•) and suppress overoxidation. Bader charge analysis, magnetic moments, and spin-polarized density of states (DOS) analyses further confirm the flexible electron transfer capability of the Fe site, which governs the catalytic activity and selectivity. This work establishes a design principle for O2-activated graphene-based dual-atom catalysts in the direct oxidation of CH4 to CH3OH and advances the development of sustainable C1 chemistry.