Catalytic Reaction Rates Controlled by Metal Oxidation State: C-H Bond Cleavage in Methane over Nickel-Based Catalysts.

The role of low concentrations of carbon complexes in hydrocarbon decomposition over transition metal surfaces has been a topic of much debate over the past decades. It is also a mystery as to whether or not electric fields can enhance hydrocarbon conversion in an electrochemical device at lower than normal reforming temperatures. To provide a "bottom-up" fundamental insight, C-H bond cleavage in methane over Ni-based catalysts was investigated. Our theoretical results show that the presence of carbon or carbide-like species at the interface between the Ni cluster and its metal-oxide support, as well as the application of an external positive electric field, can significantly increase the Ni oxidation state. Furthermore, the first C-H bond cleavage in methane is favored as the local oxidation state of Ni increases. Thus, the presence of a low concentration of carbon species, or the addition of a positive electric field will improve the hydrocarbon activation process.