No abstract

PdZn β alloy catalysts have Cu-like properties for a wide range of industrially important reactions, such as methanol synthesis, water−gas shift, and methanol steam reforming, but overcome the major disadvantages inherited by Cu such as sintering and pyrophoric nature. However, high Pd loadings (e.g., >5.0 wt %) are typically required for the synthesis of the PdZn β alloy, preventing its practical consideration as the replacement of Cu catalysts. Here, we report the synthesis of ZnAl 2 O 4 -supported PdZn β alloy catalysts at extremely low Pd loadings (e.g., 1000 ppm Pd). In particular, a cuboctahedral ZnAl 2 O 4 spinel support with exclusively polar facets provides a strong interaction between Pd and Zn, leading to PdZn β alloy formation even at low Pd loadings. A 0.1 wt % Pd/ZnAl 2 O 4 catalyst is shown to exhibit superior CO 2 selectivity (97%) in the methanol steam reforming reaction, confirming the Cu-like catalytic properties of the PdZn β alloy even at 1000 ppm Pd. The top-layer Zn species on the exposed polar facets of zinc spinel were found to play a critical role in the preferential formation of the PdZn β alloy. The advances toward the PdZn β alloy catalysts with extremely low Pd loadings bring the PdZn alloy catalysts one step closer to a wide range of applications.