Methane activation by a single iron atom supported on graphene: Impact of substrates

A density functional theory study was conducted to investigate methane activation by a single iron atom anchored on eleven different graphene substrates. It was concluded that the structure of the graphene substrate influences the catalytic activity of single iron atom for methane activation. The adsorption energy of methane on single iron atom supported on single vacancy graphene is higher than that on double vacancy graphene. Moreover, single iron atom supported on single vacancy graphene has lower energy barrier than that on double vacancy graphene for the cleavage of the first C-H bond of methane. It is noted that Fe-C and Fe-H bonds were formed for the transition states of the C-H bond breakage by single iron atom decorated on single vacancy graphene, whereas the transition states of single iron atom embedded on double vacancy graphene catalytic activation of methane does not involve the formation of Fe-H bonds. With increase of nitrogen doping, Fe -C interactions are weaker whereas C center dot center dot center dot H or N center dot center dot center dot H interactions are stronger. The energy barrier for the breakage of the first C-H bond of methane by a single iron atom supported on single vacancy graphene doped with three nitrogen atoms is lowest among all the catalysts investigated.