CO Adsorption on GaPd-Unravelling the Chemical Bonding in Real Space.

The electron localizability indicator-an efficient quantum chemical tool for analysis of chemical bonding-is applied to unveil the chemical bonding behind the CO adsorption on the (1‾ 1‾ 1‾ ) surface of the highly selective semi-hydrogenation catalyst GaPd. Refining the commonly applied Blyholder model, the obtained results are in excellent agreement with previous experimental and theoretical findings. The clean GaPd(1‾ 1‾ 1‾ ) surface presents unshielded negatively charged Pd centers and positively charged Ga species partially shielded by dangling bonds.

Order-Induced Selectivity Increase of CuPd in the Semi-Hydrogenation of Acetylene.

The two structural modifications of CuPd were synthesized as bulk powders and tested as unsupported model catalysts in the semi-hydrogenation of acetylene. The partly ordered low-temperature modification (CsCl type of structure) showed an outstanding ethylene selectivity of >90% over 20 h on stream while the disordered high-temperature modification (Cu type of structure) was 20% less selective, indicating an influence of the degree of order in the crystal structure on the catalytic properties. The results are supported by XRD and XPS experiments.