Hot-injection Synthesis of Pt-Ni Rhombic Dodecahedral Nanoframes for Oxygen Reduction Reaction Electrocatalysis

Abstract Structured Pt-TM alloys (TM = 3d -transition metals) are considered potential electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), showing enhanced catalytic activities and durability with low Pt loading. These shaped Pt-TM alloys include three-dimensional (3D) polyhedra such as octahedrons, 3D hollow structures like nanoframes (NFs), or one-dimensional nanostructures such as nanowires or nanotubes. Pt-TM alloy NFs are particularly attractive because most of the Pt on the frameworks and ridges contributes to the catalytic activity, in contrast to solid nanocrystals with buried Pt sites. In this study, Pt-Ni alloy NFs were synthesized using a hot-injection co-reduction method, starting with solid-shaped Pt-Ni rhombic dodecahedrons (RDs) and followed by etching the sacrificial Ni in acetic acid to produce Pt-Ni nanoframes. Transmission electron microscopy (TEM) confirmed the successful synthesis of large Pt-Ni RDs, which were then effectively transformed into Pt-Ni NFs featuring a uniform distribution of Pt and Ni. Electrochemical analysis revealed an electrochemically active surface area of approximately 43.2 m 2 /g Pt for the Pt-Ni NFs catalyst, with mass and specific activities measured at 0.359 A/mg Pt and 0.829 mA/cm 2 , respectively, both of which exceed the activities of the Pt-Ni RDs and commercial reference Pt/C catalysts. Graphical Abstract