Mechanistic study of dry reforming of ethane by CO2 on a bimetallic PtNi(111) model surface

Abstract

Ethane (CH₃CH₃), one of the primary components of shale gas, is an attractive candidate for the production of syngas (CO + H₂) and ethylene (CH₂CH₂) via the selective C–C and C–H bond cleavage, respectively. Understanding the origin of the selective conversion is essential to the design of a good catalyst for CH₃CH₃ activation. Herein, we combined density functional theory (DFT) calculations with kinetic Monte Carlo (KMC) simulations to shed light on the mechanism of the oxidative C–H and C–C bond cleavage of CH₃CH₃ on a PtNi(111) model catalyst using CO₂ as an oxidant, where the estimated selectivity is in good agreement with the experimental results on PtNi nanoparticles supported on CeO₂. Our calculations show that PtNi is selective to CO via direct CO₂ dissociation and the oxidative C–C bond scission of CH₃CH₃via the oxygenated (*C₂H_yO) intermediates. By comparison the CH₂CH₂ selectivity via the selective C–H bond scission of *CH₃CH₃ is much lower. The kinetic analysis suggests that the selectivity of PtNi toward syngas can be enhanced by facilitating the formation of key *C₂H_yO intermediates, while the selectivity toward CH₂CH₂ is promoted mainly by accelerating the C–H bond scission of *CH₃CH₂ to produce *CH₂CH₂.