Ethylene conversion to ethylidyne on Pd(1Â 1Â 1) and Pt(1Â 1Â 1): A first-principles-based kinetic Monte Carlo study

► Kinetic Monte Carlo simulations of ethylene conversion to ethylidyne on Pd(1 1 1) and Pt(1 1 1). ► Three mechanisms via two intermediates (from ethyl, vinyl, ethylidene, and vinylidene) studied. ► Simulations yield route via vinyl → vinylidene as main reaction path on both surfaces studied. ► Surface H produced in the reaction primarily removed as H2 from Pt(1 1 1), and as ethane from Pd(1 1 1). ► Rate-limiting steps: ethylene → vinyl on Pd(1 1 1), vinylidene → ethylidyne on Pt(1 1 1).