An alloying-degree-controlling step in the impregnation synthesis of PtRu/C catalysts

Alloying degree is a key structural parameter of PtRu catalysts for fuel cells. In this work, we demonstrate that the alloying degree of PtRu/C catalysts prepared by impregnation method can be controlled via a drying step conducted before the H-2 reduction procedure. Whereas the particle size increased only slightly with increasing drying temperature, the alloying degree changed significantly, i.e., the higher the drying temperature, the lower the alloying degree. On the basis of the results from X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements, the partial conversion of RuCl3 to RuOx during drying is attributable to the decrease in the alloying degree. The present findings can be employed to control the alloying degree in PtRu/C preparations and thus benefit the study of structure-activity relationships aimed at catalyst optimization.