There is a trend in the CH 3 * posteriors to have a slightly stronger binding energy than predicted a priori for all three models. Prior studies with -Al 2 O 3 supported rhodium nanoparticles show evidence that 1) the active sites are on the metal surface for this mechanism, not the support, and 2) CH 4 conversion both with and without gas-phase O 2 increases with decreasing particle size, which indicates that the active sites are likely edge/step sites. The lower coordination of the step sites means that species will likely bind more tightly to them.