Shape Effect of Atomically Precise Au-25 Nanoclusters on Catalytic CO Oxidation

Understanding the catalytic behavior of metal nanoclusters at the atomic level remains a major dream in nanocatalysis research. Here, we study the catalytic behavior of two different Au-25 nanoclusters (sphere vs rod) supported on TiO2 nanorods and obtain insights into the structure-property relationship for CO oxidation. The spherical [Au-25(SCH2CH2Ph)(18)](-) nanocluster exhibits a catalytic activity trend of volcano-shape with the increase of pretreatment temperature in oxygen from 150 to 300 degrees C. It is found that low-temperature pretreatment could make the cluster expose more active sites; hence, an increase in activity, while hightemperature pretreatment leads to a decrease in activity due to the thermally induced aggregation of clusters into larger particles. For the rod-shaped [Au-25(PPh3)(10)(SCH2CH2Ph)(5)X-2](2+) cluster, its activity decreases with the increase of pretreatment temperature from 150 to 300 degrees C. The different trends of spherical and rod-like Au-25 catalysts are ascribed to their distinctly different atomic packing structures. This work demonstrates a control of the atomic structure of catalysts and the effects on the catalytic performance.