Methane can be used as feedstocks for producing value-added multi-carbon hydrocarbons via the syngas-mediated Fischer-Tropsch process, yet this process requires enormous energy input for its conversion. While direct conversion of methane to value-added chemicals is a promising alternative, it is challenging due to unfavorable C-H bond activation and coke formation that deactivates catalysts. In this work, we evaluated stability and reactivity of single atom alloys (SAAs) formed by atomically doping 3d-5d transition metals on Cu(111) as catalysts for direct methane conversion to C2 hydrocarbons using density functional theory calculations. To further develop catalyst design principles for this chemistry, we systematically evaluated kinetics of methane dehydrogenation and C-C coupling steps on ten promising Cu(111)-based SAAs and unearthed descriptors that correlate with catalyst activity and selectivity. Our results show that SAA activity highly correlates with their selectivity for direct methane conversion to C2 products, highlighting the synergy between dopant and host metal in enhancing methane activation and preference towards C-C coupling. Notably, ethylene formation is kinetically favored over ethane formation across all SAAs studied. In addition, we identified C2H4 adsorption energy as an effective descriptor that guides the SAA reactivity. Based on these insights, we discovered that iridium dispersed on copper (Ir/Cu) SAA stands out as a highly active and selective catalyst for methane-to-ethylene conversion. These findings lay the groundwork for systematic and high-throughput discovery of novel SAA catalysts for methane transformation.
