A Facile Method to Synthesize Pt-Ni Octahedral Nanoparticles with Porous and Open Structure Features for Enhanced Oxygen Reduction Catalysis

In recent years, nanocatalysts with an open structure have been fascinating to use for electrocatalytic reactions due to their high specific area, large void space, and potentially highly active sites. Meanwhile, a porous structure is more beneficial to create a confined environment which would enhance catalytic activity. Herein, we show the porous Pt-Ni octahedral nanoparticles which exhibit abundant Pt-Ni alloy structures with transparent features and tiny Pt-Ni octahedral nanoparticles. By controlling the anisotropy of Pt with surfactant in solvothermal synthesis, we have synthsised composition-segregated octahedral Pt-Ni nanoparticles and tiny Pt-Ni octahedral nanoparticles at different precursor ratios. After subsequent chemical etching, the structure of composition-segregated octahedral Pt-Ni nanoparticles evolved into a porous and open structure. The porous octahedral Pt-Ni nanoparticles show similar to 7.1 times higher specific activity and similar to 5.7 times higher mass activity for the oxygen reduction reaction than that of TKK-Pt/C catalyst and 1.6 times mass activity of tiny Pt-Ni octahedral nanoparticles. The activity enhancement is attributed to the idea that some of the Pt atoms deposited on the faces of octahedron and formed a Pt-Ni alloy with Ni atoms. After chemical etching, many active sites and alloy phases are exposed to the electrochemical environment, which leads to enhanced electrochemical activity.