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Abstract

Replacing noble metals in heterogeneous catalysts by low-cost substitutes has driven scientific and industrial research for more than 100 years. Cheap and ubiquitous iron is especially desirable, because it does not bear potential health risks like, for example, nickel. To purify the ethylene feed for the production of polyethylene, the semi-hydrogenation of acetylene is applied (80 × 106 tons per annum; refs 1, 2, 3). The presence of small and separated transition-metal atom ensembles (so-called site-isolation), and the suppression of hydride formation are beneficial for the catalytic performance4, 5, 6. Iron catalysts necessitate at least 50 bar and 100 °C for the hydrogenation of unsaturated C–C bonds, showing only limited selectivity towards semi-hydrogenation7, 8, 9, 10, 11, 12, 13. Recent innovation in catalytic semi-hydrogenation is based on computational screening of substitutional alloys to identify promising metal combinations using scaling functions14 and the experimental realization of the site-isolation concept employing structurally well-ordered and in situ stable intermetallic compounds of Ga with Pd (refs 15, 16, 17, 18, 19). The stability enables a knowledge-based development by assigning the observed catalytic properties to the crystal and electronic structures of the intermetallic compounds20, 21. Following this approach, we identified the low-cost and environmentally benign intermetallic compound Al13Fe4 as an active and selective semi-hydrogenation catalyst. This knowledge-based development might prove applicable to a wide range of heterogeneously catalysed reactions.