R5 is one of the first steps in the overall mechanism, and the primary way that CH 4 adsorbs to the surface. Seen in the Supporting Information, R5 increases the selectivity of synthesis gas products and decreases full oxidation products on almost every metal, including metals that have both high and low CH 4 conversions. Full oxidation yield at the 'peak' of the volcano plot has a negative sensitivity, indicating this reaction is responsible for the 'peak' where partial oxidation occurs. R5 also plays a key role in the shape and location of the volcano, blocking methane conversion on metals with both strong carbon and oxygen binding energies. The other ways for CH 4 to adsorb to the surface, R4 and R12, were over 60% less important in determining CH 4 conversion, full oxidation yield, and partial oxidation yield than R5.