Thus, direct methane conversion to multi-carbon hydrocarbons operating at mild conditions without going through the intermediate syngas production is more economically and environmentally desirable. A variety of heterogeneous catalysts have been explored as catalytic materials for direct methane conversion, including oxidative coupling of methane over metal oxides, non-oxidative methane dehydroaromatization using zeolite-supported metal catalysts, and direct conversion through C-C coupling on metallic surfaces. Unfortunately, no practical catalysts exist today for direct methane conversion due to high C-H bond activation barriers and/or rapid catalyst deactivation by coke contamination. the surface layer of a less reactive host metal, can be used as efficient and coke-resistant catalysts for dehydrogenation of alkanes to produce alkenes. More specifically, platinum (Pt) dispersed on copper (Cu), i.e., Pt/Cu (the notation A/B denotes single atom A dispersed on host B) SAA, successfully activates desirable C-H bonds but exhibits high barriers for subsequent dehydrogenation steps that lead to coke formation, outperforming its pure metal components that Pt can activate C-H bonds, but suffer from coking, while Cu is resistant to coke formation, but exhibit high C-H activation barrier. Similarly, Rhodium (Rh) dispersed on Cu, i.e., Rh/Cu SAA, was designed as catalysts for propane dehydrogenation to propene, while either Rh or Cu pure metal is not generally considered as catalysts for alkane dehydrogenation. The primary advantage of SAAs lies in their unique geometries to decouple location of the transition state and binding sites of the reaction intermediates, allowing simultaneously favorable bond dissociations and weak binding energies, and thus enhance catalyst activity and selectivity. Moreover, the well-defined active sites in SAAs make understanding of reaction mechanisms, and thus prediction of reactivity relatively easy with density functional theory (DFT), which is the most popular computational modeling tool for heterogeneous catalysis, to accelerate discovery of catalytically efficient SAAs. Motivated by the success of SAAs for alkane dehydrogenation, we began to use DFT to design SAAs for converting methane to multi-carbon hydrocarbons through engineering 1) single catalytic sites to enable facile C-H activation and 2) host metals to allow favorable C-C coupling and weak bindings of carbonaceous deposits. Specifically, we considered various 3d-5d transition metal atoms dispersed on Cu(111) surface as catalysts for direct methane conversion to C2 products, including ethane (C2H6), ethylene (C2H4), and acetylene (C2H2). Cu was selected as the host metal due to its kinetically favorable C-C coupling and weak bindings to adsorbates. Here, we started from studying the stabilities of these Cu-based SAAs in terms of avoiding dopant aggregation and segregation. On stable SAAs, we then evaluated thermodynamics and performed detailed kinetics modeling of methane dehydrogenation to atomic carbon and multiple C-C coupling mechanisms between carbonaceous species, towards the ultimate goal of identifying active, selective, and coke-resistant SAAs for methane utilization.