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.