Atomic-Scale Structure and Catalysis on Positively Charged Bimetallic Sites for Generation of H2.

Here, we report that a cationic bimetallic site consisting of one Pd and three Zn atoms (Pd1Zn3) supported on ZnO (Pd1Zn3/ZnO) exhibits an extraordinarily high catalytic activity for the generation of H2 through methanol partial oxidation (MPO) that is 2-3 orders of magnitude higher than that of a metallic Pd-Zn site on Pd-Zn nanoalloy (Pd-Zn/ZnO). Computational studies uncovered that the positively charged Pd atom of the subnanometer Pd1Zn3 bimetallic site largely decreases the activation barrier for dehydrogenation of methanol as compared to a metallic Pd atom of Pd-Zn alloy, thus switching the rate-determining step of MPO from methanol dehydrogenation over a Pd-Zn alloy with high barrier to the O2 dissociation step on a cationic Pd1Zn3 site with a low barrier, which is supported by our kinetics studies. The significantly higher catalytic activity and selectivity for H2 production over a cationic bimetallic site suggest a new approach to design bimetallic catalysts.