Phase conversion of Pt3Ni2/C from disordered alloy to ordered intermetallic with strained lattice for oxygen reduction reaction

Abstract Tuning the surface strain and atom arrangement to control the surface chemistry process is one of efficient strategies to enhance the electrocatalytic performance of nanomaterials. This research introduces an ordered Pt 3 Ni 2 /C intermetallic nanoparticle as a new type of the Pt-Ni system for the ORR, which is rarely reported at present. Besides, it focuses on the phase conversion of Pt 3 Ni 2 /C nanocatalysts from a disordered phase to an ordered phase. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirm the formation of ordered face-centered cubic (fcc) type Pt 3 Ni 2 /C nanocatalysts with homogeneous particle distribution and average crystallite size of 6.4 nm. The ordered fcc-Pt 3 Ni 2 /C exhibits improved electrocatalytic activities toward the oxygen reduction reaction (ORR) in 0.1 M HClO 4 and 0.1 M KOH electrolyte when compared with Pt 3 Ni 2 /C disordered alloy. Besides, the robust ordered fcc-Pt 3 Ni 2 /C showed a smaller activity loss after durability tests in alkaline medium than acid electrolyte. The improved ORR activity and stability could be ascribed to the surface atom arrangement and reasonable surface strain originated from the ordered structure of Pt 3 Ni 2 /C nanoparticles relative to the disordered Pt 3 Ni 2 /C alloy, forcefully demonstrating that the Pt 3 Ni 2 /C intermetallic compound may act as highly efficient ORR electrocatalysts in energy conversion process.