DFT Study On Dry Reforming Of Methane Over Ni₂Fe Overlayer Of Ni?111? Surface

Dry reforming of methane?DRM?is of significant importance in recent years,because it consumes two major greenhouse gases,carbon dioxide and methane,and provides ways to convert them into hydrocarbons,Fischer-Tropsch synthesis products and other high-value products.Numerous experiments showed that noble metals such as Pd,Rh and Pt,Ru,Ir have good catalytic activity for DRM,but expensive price and low abundance limit their practical application.Ni-based catalysts have become the hot catalysts for studying DRM due to their low cost and relatively high activity.However,the severe problem for using Ni-based catalysts is the rapid deactivation caused by carbon deposition.Therefore,looking for a catalyst with high activity and anti-carbon ability is the current direction of DRM.This paper reported the reaction mechanism of dry reforming of methane on the Ni₂Fe overlayer of Ni?111?surface,and discussed the influence of Fe on the catalytic activity.The main results are as follows:We reported the complete catalytic cycle of dry reforming of methane on Ni₂Fe overlayer of Ni?111?surface by periodic density functional theory?DFT?calculations.The pathways for dehydrogenation of CH₄ and CO₂ activation were located.Our results demonstrate that compared with pure Ni?111?surface,the introduction Fe into Ni increases the energy barrier of CH dissociation to carbon and hydrogen atoms,thereby suppressing coke deposition on the surface,while it promotes the H-induced CO₂ activation pathway to form OH radical,and thus not only the surface oxygen atoms but also OH radicals are responsible for the oxidation of CH and C on the Ni₂Fe overlayer.The most favorable pathway of CH/C oxidation is found to be CH*+OH*?CHOH*?CHO*+H*?CO*+2H*,with the rate-limiting energy barrier of 1.12 eV.Furthermore,since Fe is oxidized partially to FeO leading to a partial dealloying under DRM conditions incording to experiments,we also studied the surface-carbon removal and the activity for the reforming of methane on the FeO ribbon supported Ni?111??FeO/Ni?interface by DFT+U method.The surface C reacts with lattice oxygen of FeO to produce CO via a Mars-van Krevelen?MvK?mechanism,with a very lower energy barrier of 0.16 eV.The present results show that the introduction of Fe into Ni has a positive effect on the activity toward DRM and has an improved coke resistance.