Octahedral PtNi nanoparticles with controlled surface structure and composition for oxygen reduction reaction

Abstract

Controlling the surface structure and composition at the atomic level is an effective way to tune the catalytic properties of bimetallic catalysts. Herein, we demonstrate a generalized strategy to synthesize highly monodisperse, surfactant-free octahedral PtxNi1−x nanoparticles with tunable surface structure and composition. With increasing the Ni content in the bulk composition, the degree of concaveness of the octahedral PtxNi1−x nanoparticles increases. We systematically studied the correlation between their surface structure/composition and their observed oxygen reduction activity. Electrochemical studies have shown that all the octahedral PtxNi1−x nanoparticles exhibit enhanced oxygen reduction activity relative to the state-of-the-art commercial Pt/C catalyst. More importantly, we find that the surface structure and composition of the octahedral PtxNi1−x nanoparticles have significant effect on their oxygen reduction activity. Among the studied PtxNi1−x nanoparticles, the octahedral Pt1Ni1 nanoparticles with slight concaveness in its (111) facet show the highest activity. At 0.90 V vs. RHE, the Pt mass and specific activity of the octahedral Pt1Ni1 nanoparticles are 7.0 and 7.5-fold higher than that of commercial Pt/C catalyst, respectively. The present work not only provides a generalized strategy to synthesize highly monodisperse, surfactant-free octahedral PtxNi1−x nanoparticles with tunable surface structure and composition, but also provides insights to the structure-activity correlation.

The oxygen reduction on Pt-Ni and Pt-Ni-M catalysts for low-temperature acidic fuel cells: A review

“…The oxygen reduction on large‐scale octahedral Pt x Ni catalysts was widely investigated . The most part of these shaped Pt‐Ni nanoparticles was prepared using a polyol reduction process with platinum and nickel acetylacetonates (Pt (acac) 2 and Ni (acac) 2 , respectively) as metal precursors in the presence of surfactants such as oleylamine, oleic acid, octylamine, dodecylamine, and hexadecylamine (HDA) .…”

“…The presence of organic surfactants limits the free access of surface active sites and hinders the electron transport between the catalyst and the support, resulting in a decrease of the ORR performance. Thus, surfactant‐free methods for the synthesis of octahedral Pt‐Ni electrocatalysts were developed . Zhang et al prepared carbon‐supported Pt‐Ni/C octahedra simply by impregnating both platinum and nickel acetylacetonates onto a carbon support, followed by reduction at 200°C under a CO/H 2 atmosphere.…”

“…The oxygen reduction on large-scale octahedral Pt x Ni catalysts was widely investigated. [85][86][87][88][89][90][91][92][93][94][95][96][97][98] The most part of these shaped Pt-Ni nanoparticles was prepared using a polyol reduction process with platinum and nickel acetylacetonates (Pt (acac) 2 and Ni (acac) 2 , respectively) as metal precursors in the presence of surfactants such as oleylamine, oleic acid, octylamine, dodecylamine, and hexadecylamine (HDA). [85][86][87][88][89][90][91] The edge length of the octahedral PtNi catalysts can be controlled by tuning the oleylamine content used in the synthesis process.…”

“…Thus, surfactant-free methods for the synthesis of octahedral Pt-Ni electrocatalysts were developed. [92][93][94][95][96][97][98] Zhang et al 92 prepared carbon-supported Pt-Ni/C octahedra simply by impregnating both platinum and nickel acetylacetonates onto a carbon support, followed by reduction at 200°C under a CO/H 2 atmosphere. The presence of CO is essential for the formation of octahedral Pt-Ni.…”

Constrained-volume assembly of organometal confined in polymer to fabricate multi-heteroatom doped carbon for oxygen reduction reaction

“…Currently, Pt based nanomaterials are considered to be the most efficient electrocatalyst for cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) [3,4]. Nevertheless, high cost, limited supply, and low stability of Pt catalyst still greatly hamper their commercialization.…”