Selective Conversion of CH4 by MAl2O4− (M = Au and Pd): A Theoretical Study

The catalytic reactions of individual noble metal atoms can offer theoretical guidance for the design of the relevant single-atom catalysts. In this paper, from MD adsorption simulation, both Au and Pd atoms rather bond to Al than O atoms of the employed Al₂O₃ (001) surface and display more active sites for the Au system with respect to the Pd system. Next, a detailed comparative study was conducted on the reactions of preferred MAl₂O₄⁻ (M = Au and Pd) with CH₄ using the DFT-B3LYP functional. The obtained results reveal that in the AuAl₂O₄⁻ reaction, the CH₄ tends to be transformed into syngas, H₂ and CO. In contrast, the formaldehyde is generated in the reaction of PdAl₂O₄⁻ + CH₄. Additionally, our findings also suggest that the reactivity of AuAl₂O₄⁻ is significantly higher than that of PdAl₂O₄⁻, indicating that the former can fully activate CH₄ four C─H bonds. This insight provides valuable guidance for the rational design of single-atom catalysts aimed at selective CH₄ conversion.