Molten-Salt Synthesis of Pt₃Co Binary Alloy Nanoplates as Excellent and Durable Electrocatalysts toward Oxygen Electroreduction

Although Pt₃M (M = transition metals such as Co, Ni, Cu) binary alloy nanostructures have been well established with reference to their unique composition (chemically ordered) and electrocatalytic property relationship, further improvement in their catalytic efficiency could be possible by tuning the surface properties. Herein, to improve the sluggish kinetics of electroreduction of oxygen, we demonstrate an effective way to prepare carbon-supported Pt₃M nanostructures, especially Pt₃Co using a single-step, molten-salt synthesis (MSS) method, without using any capping or stabilizing agent. X-ray powder diffraction (XRD) studies confirm alloy formation in Pt₃Co with a face-centered cubic (fcc) structure (but surprisingly not a chemically ordered structure or L₁₂ phase) and transmission electron microscopy (TEM) reveals the formation of hexagonal nanoplates with approximately 2 nm thickness and ∼17 nm diameter. The specific geometry and facets (surface properties) are responsible for boosting the specific activity to 4.2 mA cm_Pt^–2, which is almost 21 times greater than that of the state-of-the-art Pt/C catalyst and even superior to those of the Pt₃Ni/C and Pt₃Cu/C catalysts (prepared by a similar process). Moreover, an increase in the electrocatalytic activity is observed during the durability test that is perceptible due to the formation of Pt-surface segregation and Pt-skin after slight dissolution of transition-metal atoms from the surface, which is also confirmed using a Q_CO/2Q_H indicator ratio.