Unifying Activity and Selectivity in Fischer–Tropsch Catalysis via the Valence Electron Configuration Descriptor

Fischer–Tropsch (F-T) synthesis is a cornerstone of C1 chemistry, yet predicting its complex activity trends and highly diverse product selectivity, spanning methane (CH4), olefins, long-chain alkanes, and oxygenates, remains a formidable challenge in fundamental heterogeneous catalysis. Recently, we demonstrated that valence electronic configuration serves as an effective descriptor for rationalizing catalytic trends in the hydrogen evolution reaction (HER) and ammonia synthesis. Herein, we extend this framework, centered on the availability of surface half-filled orbitals (HFOs), to systematically unravel the mechanisms governing atomic carbon generation, overall catalytic activity, and product selectivity in F-T synthesis. We show that the unique HFO count of surface transition metal atoms acts as a spatial and electronic template that dictates the feasible bond-cleaving and bond-making pathways. On nickel (Ni, Group 10, two HFOs), HFO limitations restrict surface reactions strictly to sequential C–H coupling, resulting in near-exclusive CH4 production (methanation). Cobalt (Co, Group 9, three HFOs) possesses the necessary availability of three HFOs to accommodate concurrent C–C and C–H bond formation, facilitating long-chain alkane growth. Meanwhile, iron (Fe, Group 8, four HFOs) can coordinate multiple reactant species, enabling both hydrogen-assisted reduction and the Boudouard disproportionation reaction (2CO ⇌ C + CO2). Furthermore, temperature-induced variations in surface hydrogen coverage over Fe selectively drive C═C double-bond formation to yield light olefins under hydrogen-limited conditions, or allow undissociated CO insertion to form oxygenated products. Integrating this orbital-template model with the classical Sabatier principle rationalizes the inactivity of late noble metals (due to insufficient carbon binding) and early transition metals (due to irreversible carbide poisoning of the HFOs). By correlating macroscopic catalytic performance directly with a quantifiable, intrinsic atomic property, this work establishes a predictive a priori roadmap for the rational design of advanced catalysts with high activity and targeted product selectivity.