Cr/Cu SAAs. The selection of Ni/Cu, Rh/Cu, and Cr/Cu SAA catalysts for direct methane conversion to multi-carbon hydrocarbons is guided by thermodynamics of CH4 dehydrogenation and C-C coupling mechanisms. To fully understand their reactivities, evaluation of kinetics, i.e., predicting reaction barriers, is essential. We started from optimizing MEP on Ni/Cu SAA (Figure ). The initial dehydrogenation step of CH4 to *CH3 starts from a desorbed CH4 molecule on top of the SAA surface and then undergoes C-H bond breaking close to the Ni dopant site at the transition state towards forming an adsorbed *CH3 at an atop site and a *H at a hollow site. This C-H activation step is both thermodynamically and kinetically favorable with a reaction energy of 0.11 eV and a barrier of 0.77 eV (Figure ), indicating that this step can proceed under mild conditions. The second dehydrogenation step (*CH3 to *CH2) proceeds via a transition state of C-H bond breaking close to the Ni dopant site towards both products (i.e., *CH2 and *H) moving to hollow sites with a reaction energy of 0.48 eV and a barrier of 0.75 eV (Figure ). The competing C-C coupling between two *CH3 intermediates to form ethane is thermodynamically more favorable with a reaction energy of -0.18 eV, but kinetically less favorable with a higher barrier of We then studied Cr/Cu SAA (Figure , SI Figure ). The first dehydrogenation step is energetically favorable with a reaction energy of 0.08 eV and a barrier of 0.64 eV (Figure ). The second dehydrogenation step has a reaction energy of 0.48 eV and a barrier of 0.76 eV. Similarly to the other two SAAs, *CH3 coupling is kinetically unfavorable with a sufficiently high barrier of 1.43 eV, indicating *CH2 as the only possible product. The subsequent dehydrogenation of *CH2 to *CH proceeds with a reaction energy of -0.09 eV and a barrier of 0.47 eV. However, C-C coupling of two *CH2 to ethylene is even more favorable with a similar reaction energy of -0.12 eV and a lower barrier of 0.28 eV, suggesting that ethylene is a product for methane conversion on Cr/Cu SAA. Further reactions to either *C and acetylene are impossible with very high reaction energies. Therefore, Cr/Cu also emerges as an efficient catalyst for direct methane conversion to ethylene.