Constructing water-resistant phase-pure alloy carbide for boosting syngas to olefins.

Fischer-Tropsch synthesis offers a promising route for sustainable olefins production. However, a persistent challenge lies in the presence of water-a natural byproduct that oxidizes the active iron carbide phase and triggers the competing water-gas shift side reaction, ultimately capping olefins yield below 37%. In this study, we propose a strategy to tailor the adsorption and reaction behaviors of water by constructing phase-pure alloy carbide. Substituting cobalt into the Fe5C2 lattice rearranges the adsorption geometry of water molecules on metal carbide, making water more prone to desorb rather than dissociate. This key change endows the catalyst with superior resistance to oxidation by water vapor and low water-gas shift reactivity. Thus, near-complete carbon monoxide conversion (99%) and an unprecedented olefins yield of 47% are achieved under a mild reaction temperature of 280 °C, opening new avenues for efficient olefins synthesis.