(513x) The Kinetics and Trends in Promoted Methane Dry Reforming on Dual-Site Co3Mo3n Catalysts

The dry reforming of methane (DRM) catalysis offers an enticing route that enables the utilization of CH₄ and CO₂. The long-standing issue in DRM remains to be (1) CH₄ activation and (2) coke-induced catalyst deactivation. Hence, the efficiency of DRM catalysts depends on their functionality to handle both aspects. Transition metal particles supported on reducible oxides results in various efficacy from extensive studies. Recently, it has been shown that the monolithic ternary nitrides such as Co₃Mo₃N, Ni₃Mo₃N, in a non-conventional architecture, exhibit significantly higher reactivity, stability, and resistance to carbon deposition for CO₂ DRM. Preliminary work attributed their observations to the synergistic interactions of the Co- and Mo-containing components.

In this work, catalyst models derived from Co₃Mo₃N were employed to investigate the molecular mechanism of DRM on its two distinctive active sites using periodic Density Functional Theory (DFT) and microkinetic modeling. We focused on the catalysis taking place on the native Co and Mo_xN domains in Co₃Mo₃N(111). DFT calculations revealed that CH₄ activation prefers the Co site, while the CO₂ activation prefers the Co-Mo₃N boundary site. The difference in site preference favors the promotion of parallel CH₄ and CO₂ activation and conversion routes. More importantly, the coexistence of these domain sites is effective in CH₄ activation and removal of carbonaceous species (i.e., C, CH), and fundamentally enables a rather superior reactivity and the much-desired coke resistance during DRM. Principal component analysis (PCA) was performed to determine that binding energies of C and O are appropriate catalytic descriptors. Also, the predicted turnover frequencies (TOFs) on the Co₃Mo₃N model catalyst confirmed that the dual-site catalysis is superior over monofunctional transition metal catalysts. The molecular insights into the DRM chemistry on Co₃Mo₃N(111) helps to further design and optimize the multi-component catalytic materials with catalytic distinct surface active sites