Development of alloys replacing rare metals for catalysis

在甲醇水蒸气重整反应中，PdZn和Cu表现出相当的催化选择性，反映了它们在费米能级附近相似的电子结构。对M-Zn（M=Pd，Ni，Pt）合金化的第一性原理计算表明，Zn的加入使M元素的d带宽度发生了剧烈的变化，从而使M元素具有与Cu相似的电子结构。d带宽度的减小是M-M对缺失和晶格畸变的结果。本文对M_ Zn_2金属间化合物合金粉末和M/ZnO样品的SRM、CO和H_2吸附进行了测量<50><50>，并证实了由电子态密度（DOS）计算得到的化学性质是预期的。采用浸渍合金化法成功制备了无负载介孔金属间化合物NiZn和PdZn催化剂。所得合金催化剂的比表面积达到~ 20 m^2/g。甲醇水蒸气重整反应（SRM）的催化性能与未负载的多孔Ni和Pd催化剂完全不同，NiCu和PdZn催化剂上甲醇和SRM的分解优先发生。在反应的选择性方面，NiCu与Pd非常相似，并且它们在价态DOS上的相似性得到了验证，表明本研究中提出的想法是可行的。

PdZn shows comparable catalytic selectivity to Cu in steam-reforming of methanol (SRM)reaction reflecting their similar electronic structures near the Fermi level (E_F). First-principles slab calculations for M-Zn (M=Pd, Ni, Pt)reveal that alloying with Zn leads to drastic change in the d-band width of M elements and it is essential for a similar electronic structure to Cu. The reduction of the d-band width is a consequence of the missing M-M pair and the lattice distortion. Measurements for SRM, CO and H_2 adsorptions have been performed for alloy powders of M_<50> Zn_<50> intermetallic compounds and M/ZnO samples and has been verified that chemical properties are expected from calculated electronic density of states (DOS). Unsupported mesoporous intermetallic NiZn and PdZn catalysts are successfully prepared by means of immersion alloying process. The surface areas of resultant alloy catalysts reached over ~ 20 m^2/g. The catalytic properties for steam reforming of methanol (SRM)were completely different from the original unsupported porous Ni and Pd, where the decomposition of methanol and the SRM occurred preferentially on NiCu and PdZn. In terms of selectivity of the reaction, NiCu is very similar to Pd and their similarity in valence DOSs was verified, indicating availability of the idea developed in the present research.