Revealing Electronic Influences in the Semihydrogenation of Acetylene

The electronic influence on the catalytic properties in the semihydrogenation of acetylene is addressed by applying unsupported intermetallic materials from the solid solution Ga1-xSnxPd2 (0 <= x <= 1). Due to the only marginal changes in the crystal structure, the whole series shows excellent selectivity to ethylene (similar to 85%) comparable with the binary GaPd2. Moreover, the incremental addition of up to one electron per formula unit reveals a maximum in the specific catalytic activity around the nominal composition with x = 0.28 corresponding to 4.0 atom % tin in the near-surface region, as revealed by operando X-ray photoelectron spectroscopy measurements. The study shows a reliable and quantitative relation between the d-band shift and catalytic activity, revealing once more the potential of intermetallic compounds in heterogeneous catalysis.