Complex intermetallic compounds such as transition metal (TM) aluminides are promising alternatives to expensive Pd-based catalysts, in particular for the semi-hydrogenation of alkynes or alkadienes [1,2]. The gas-phase butadiene hydrogenation performances of several quasicrystalline approximant surfaces, namely o-Al13Co4(100), m-Al13Fe4(010) and m-Al13Ru4(010), were investigated. In addition, two low-index surfaces [(100) and (010)] of o-Al13Co4 were compared to determine effect of the surface orientation on the catalytic performances. The following roomtemperature activity order is: Al13Co4(100) ≪ Al13Co4(010) < Al13Ru4(010) < Al13Fe4(010). Al13Co4(010) is the most active surface at 110 °C, and even more selective to butene (100%) than Al13Fe4(010) [2,3]. These experimental observations are further discussed in light of DFT calculations. The butadiene and butene adsorption energies are shown to be useful to rationalize the catalytic measurements. Moreover, electronic structure calculations suggest that isolating the TM active centers within the Al matrix induces a narrowing of the TM d-band, which leads to the high catalytic performances of Al13TM4 compounds [3]. References [1] M. Armbrüster et al., Al13Fe4 as a low-cost alternative for palladium in heterogeneous hydrogenation, Nat. Mater., 11, 690–693 (2012). [2] L. Piccolo, Al13Fe4 selectively catalyzes the hydrogenation of butadiene at room temperature, Chem. Commun. 49, 9149–9151 (2013); L. Piccolo and L. Kibis, The partial hydrogenation of butadiene over Al13Fe4 : A surface-science study of reaction and deactivation mechanisms, J. Catal. 332, 112–118 (2015). [3] L. Piccolo et al., Catalytic properties of Al13TM4 complex intermetallics: influence of the transition metal and the surface orientation on butadiene hydrogenation, Sci. Technol. Adv. Mater. 20, 557-567 (2019).