Halogen Fluorine Unlocks Ru Activity for Olefins Production from Syngas

Olefins production from syngas via Fischer–Tropsch synthesis requires catalysts that favor olefins formation, maintain intrinsic activity, and suppress CO2 and CH4 formation. Sodium-promoted ruthenium nanoparticles shift the product distribution toward α-olefins but suppress Ru activity by more than 90%, necessitating higher Ru loadings. We show that incorporating inorganic fluorine into Na-promoted Ru catalysts increases activity 2.5-fold while maintaining 72.1% α-olefins selectivity and ∼5.0% combined selectivity to CO2 and CH4. At a Ru loading of 1.26 wt %, the catalyst achieves a Ru time yield of 1.14 molCO·gRu–1·h–1 and olefins space-time yield of 1516.1 g·molRu–1·h–1, outperforming most reported Ru-based catalysts. Fluorine also restores activity in Fe- and Co-based systems. Mechanistic studies indicate that surface Na–F cation–anion pairs modulate the electronic structure, weaken Ru-CO binding, and generate hydrogen species that accelerate CO activation and suppress olefins hydrogenation. This work established a halogen-mediated strategy to address the activity–selectivity trade-off in sodium-promoted syngas conversion.