Abstract
Pt–Ni nanostructures are a class of important electrocatalysts for polymer electrolyte membrane fuel cells. This work reports a systematic study on the reaction mechanism of the formation of Pt–Ni seed-core-frame nanostructures via the seeded co-reduction method involving the Pt seeds and selective co-reduced deposition of Pt and Ni. The resultant structure consists of a branched Pt ultrafine seed coated with a pure Ni as rhombic dodecahedral core and selective deposition of Pt on the edges of the cores. Both the type of Pt precursor and the precursor ratio of Pt/Ni are critical factors to form the resulting shape of the seeds and eventually the morphology of the nanostructures. These complex hierarchical structures can be further graved into hollow Pt–Ni alloy nanoframes using acetic acid etching method. The larger surface area and higher number of low coordinate sites of the nanoframes facilitate the electrocatalytic activity and stability of Pt–Ni alloy for methanol oxidation as compared to their solid counterparts. This study elucidates the structural and compositional evolution of the complex nanoarchitectures and their effects on the electrocatalytic properties of the nanostructures.
Highlights
Platinum (Pt)-containing nanoparticles have attracted tremendous attentions in recent years because of their intriguing properties and broad potential applications in polymer electrolyte membrane fuel cells (PEMFCs) [1,2]
To improve electrocatalytic activity with cost effectiveness, 3d-transition metals are incorporated into the pure Pt lattice to form Pt-based bimetallic catalysts for PEMFC
Aliphatic amines were used as both reductant and solvent, and a sequential injection method was applied to control the growth of the desired nanostructures
Summary
Platinum (Pt)-containing nanoparticles have attracted tremendous attentions in recent years because of their intriguing properties and broad potential applications in polymer electrolyte membrane fuel cells (PEMFCs) [1,2]. To improve electrocatalytic activity with cost effectiveness, 3d-transition metals are incorporated into the pure Pt lattice to form Pt-based bimetallic catalysts for PEMFC. Pt3 Ni(111) surface was demonstrated to be 10- and 90-fold more active than the Pt(111) surface and the commercial Pt/C catalysts, respectively, for the cathodic oxygen reduction reaction (ORR) of PEMFCs [3]. Many efforts have been made to synthesize Pt–Ni nanoparticles with various sizes, shapes, and compositions for improvement of ORR catalytic activity. The Pt3 Ni octahedral nanoparticles showed ~4 times better than the commercial Pt/C catalysts [4,5]. While the ORR activity of Pt3 Ni octahedra was found ~5-fold higher than that of the nanocubes with similar size [6]. A nominal composition of PtNi nanoparticles displayed a 3-fold more active than
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