Carbon-hydrogen bond cleavage, activation barrier

M-C interaction in the product as well as reactant state results in weaker interaction between reacting hydrocarbon fragments, so that barriers for the reaction in both directions increase. This in line with the observed lower rate of hydrocarbon hydrogenolysis observed for Pt as compared with Ni. On Ni the rate of C-H activation is lowered more than that for the CH -CHy bond cleavage reaction. Because of the stronger metal-carbon bond of Pt than Ni, the rate of methane formation by recombination of adsorbed hydrogen with adsorbed CH3 will be lower on the former. 

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