Revealing the Reactivity-Stability Trade-off in the Dry Reforming of Ethane over Ni Surfaces from the Microkinetic Analysis of Complex Reaction Network

Dry reforming of ethane (DRE) with carbon dioxide, a
key reaction
for converting shale gas into value-added products, offers an efficient
route for carbon resource utilization. This process proceeds through
two competing pathways: C–C bond cleavage leading to syngas
formation and oxidative dehydrogenation yielding ethylene. Achieving
precise control over product selectivity while maintaining catalyst
stability through catalyst design remains a major challenge. In this
study, we combine density functional theory (DFT) calculations with
microkinetic modeling to elucidate the structure-performance relationship
of DRE on Ni(111) and Ni(211) surfaces. A comprehensive reaction network
comprising 52 intermediates, 139 transition states, and 141 elementary
steps is constructed for the DRE reaction. The Ni(111) terraces promote
sequential dehydrogenation to CH2CH2*, resulting
in approximately 60% ethylene selectivity with minimal coke formation.
In contrast, the Ni(211) step edges exhibit superior C–C bond
activation and enhanced syngas selectivity but also strongly adsorb
carbonaceous intermediates (C*, CC*, CCH*), leading to significant
carbon accumulation and catalyst deactivation. Kinetic analyses reveal
that the coverage-dependent balance between forward and reverse reaction
rates is the primary factor governing selectivity. These findings
establish a fundamental reactivity-stability trade-off in Ni-catalyzed
DRE, and possible strategies to optimize catalytic activity, selectivity,
and coke resistance are proposed.