First principles calculation of CH4 decomposition on nickel (111) surface

The mechanism of the CH4 decomposition on the nickel (111) surface is investigated by first principles calculations. The activation energy of each reaction is calculated using nudged elastic band method. The activation energy of hydrogen dissociation from a CH2 fragment is found much lower than the one of a CH3 fragment. This result is consistent with the fact, observed in our previous molecular dynamics (MD) simulations, that the CH3 fragment is dissociated into a CH fragment and two hydrogen atoms spontaneously. The effects of finite temperature at 1500 K on the decomposition reaction of a CH4 molecule and its fragments are also investigated using constraint MD method. While the temperature effects are barely visible in CH4 and CH2 dissociation processes, they reduce the activation free energy of hydrogen dissociation from CH3 and CH fragments largely.