Reaction Mechanism of Rapid CO Electroreduction to Propylene and Cyclopropane (C₃₊) over Triple Atom Catalysts

The carbon monoxide reduction reaction (CORR) toward C₂₊ and C₃₊ products such as propylene and cyclopropane can not only reduce anthropogenic emissions of CO and CO₂ but also produce value-added organic chemicals for polymer and pharmaceutical industries. Here, we introduce the concept of triple atom catalysts (TACs) that have three intrinsically strained and active metal centers for reducing CO to C₃₊ products. We applied grand canonical potential kinetics (GCP-K) to screen 12 transition metals (M) supported by nitrogen-doped graphene denoted as M3N7, where M stands for Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au. We sought catalysts with favorable CO binding, hydrogen binding, and C-C dimerization energetics, identifying Fe3N7 and Ir3N7 as the best candidates. We then studied the entire reaction mechanism from CO to C₃H₆ and C₂H₄ as a function of applied potential via, respectively, 12-electron and 8-electron transfer pathways on Fe3N7 and Ir3N7. Density functional theory (DFT) predicts an overpotential of 0.17 V_RHE for Fe3N7 toward propylene and an overpotential of 0.42 V_RHE toward cyclopropane at 298.15 K and pH = 7. Also, DFT predicts an overpotential of 0.15 V_RHE for Ir3N7 toward ethylene. This work provides fundamental insights into the design of advanced catalysts for C₂₊ and C₃₊ synthesis at room temperature.