We next investigated possible C-C coupling steps towards producing C2 hydrocarbons, including ethane, ethylene, and acetylene. We considered coupling between two *CH3 intermediates to ethane, two *CH2 intermediates to ethylene, and two *CH intermediates to acetylene on 16 stable SAAs (Figure , SI Table ). Similarly to CH4 dehydrogenation steps, dopants in SAAs affect the activity of C-C coupling steps, leading to wide ranges of reaction energies: -1.95 eV (Hg/Cu) to 0.87 eV (Hf/Cu) for ethane formation; -1.96 eV (Hg/Cu) to 1.05 eV (Hf/Cu) for ethylene generation; -0.94 eV (Au/Cu) to 1.76 eV (Zr/Cu) for acetylene production (SI Table ). Interestingly, we observed divergent trends from dehydrogenation steps that SAAs with dopants from late transition metals are more reactive for C-C coupling. That is to say, outershell d-electron configuration of dopants in SAAs also serves as a descriptor for C-C coupling reactivity. Indeed, we found strong correlation that reaction energies of all three C-C coupling steps become more negative with increasing number of outer-shell d-electrons of dopants (SI Figure ). Selectivity analysis. Overall, Cu(111)-based SAAs exhibit inverse correlation between CH4 dehydrogenation and C-C coupling steps (SI Figure ), i.e., reactive SAAs for C-H bond activation are inert for C-C coupling and vise versa. Therefore, SAAs with dopants from mid-row transition metals that balance well between two types of chemistry are potential active and selective catalysts for direct methane conversion to multi-carbon hydrocarbons. To quantitatively analyze SAA activity and selectivity, we compared both the first CH4 dehydrogenation energy (i.e., CH4 to *CH3) and an energy difference, ΔE, between reaction energies of the second dehydrogenation step (i.e., *CH3 to *CH2) and the two *CH3 coupling reaction (Figure ). A low CH4 dehydrogenation energy indicates that the catalyst is active for initial C-H bond breaking, while a high ΔE means that the catalyst is selective for C-C coupling towards ethane formation while suppressing further dehydrogenation. Following this analysis, we defined a SAA simultaneously with less than 0.15 eV for CH4 dehydrogenation and greater than 0.45 eV for ΔE as an active and selective catalyst for direct methane conversion, and found that Ni/Cu, Cr/Cu, and Rh/Cu SAAs fall in this region that can potentially transform methane to multi-carbon hydrocarbons (Figure ).