Methane decomposition to produce molecular hydrogen and solid carbon was catalyzed by contact with molten KCl:MnCl2 mixtures in a bubble column reactor from 700 to 1050 degrees C. The apparent activation energy decreased from approximately 300 kJ/mole for pure KCl to 161 kJ/mole in a 67:33 mol % mixture of KCl:MnCl2. At 30% methane conversion, pyrolysis in the KCl:MnCl2 melt at 1050 degrees C had high hydrogen selectivity ((similar to)99%) in comparison to pure molten KCl ((similar to)90%), which was observed to produce multiple hydrocarbon co-products. The pyrolysis activity of the KCl:MnCl2 melt remained stable for over 30 h and produced a separable, highly graphitic carbon solid that accumulated at the surface of the higher-density salt melt.