Controlled Synthesis of PtNi Hexapods for Enhanced Oxygen Reduction Reaction.

Xing Song,Zewei Quan,Xixia Zhao,Qi Yang,Xiaokun Fan,Min Tang,Shuiping Luo,Wen Chen

doi:10.3389/fchem.2018.00468

Xing Song, Zewei Quan + Show 6 more

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https://doi.org/10.3389/fchem.2018.00468

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Abstract

Well-defined PtNi nanocrystals represent one of the most efficient electrocatalysts to boost the oxygen reduction reaction (ORR), especially in the shape of octahedrons, nanoframes, and nanowires. However, the synthesis of complex PtNi nanostructure is still a great challenge. Herein, we report a new class of PtNi hexapods with high activity and stability toward ORR. The hexapods are prepared by selective capping and simultaneous corrosion. By controlling the oxidative etching, PtNi polyhedrons and nanoparticles are obtained, respectively. The intriguing hexapods are composed of six nanopods with an average length of 12.5 nm. Due to their sharp tips and three-dimensional (3D) accessible surfaces, the PtNi hexapods show a high mass activity of 0.85 A mg at 0.9 V vs. RHE, which are 5.4-fold higher than commercial Pt/C, also outperforming PtNi polyhedrons and PtNi nanoparticles. In addition, the mass activity of PtNi hexapods maintains 92.3% even after 10,000 potential cycles.

Highlights

Proton exchange membrane fuel cells (PEMFCs) represent as one of the most promising clean energy technologies for electric vehicles, but the high cost of components and the sluggish kinetics of oxygen reduction reaction (ORR) hinder its broad deployment, especially when the expensive and scarce Platinum (Pt) is used as catalyst (Gasteiger et al, 2005)
The pod-like features in the nanocrystals can be clearly observed by Transmission electron microscope (TEM) and STEM
To confirm the hexapod morphology in more details, we acquired a set of tilted TEM images at different α direction and illustrated their structure models

Summary

Introduction

Proton exchange membrane fuel cells (PEMFCs) represent as one of the most promising clean energy technologies for electric vehicles, but the high cost of components and the sluggish kinetics of oxygen reduction reaction (ORR) hinder its broad deployment, especially when the expensive and scarce Platinum (Pt) is used as catalyst (Gasteiger et al, 2005). Intensive efforts have been focused on improving the activity, stability and utilization of Pt catalyst (Huang et al, 2015; Zhang et al, 2015a; Wang et al, 2018). Markovicand co-workers have reported that the bulk alloy of Pt3Ni composition with Pt (111)-skin exhibits greatly enhanced ORR activity compared with Pt. PtxNi alloy nanocrystals have been widely developed and which show the best catalytic performance toward ORR, outperforming the commercial Pt/C and other Ptbased catalysts with different component (Stamenkovic et al, 2007a,b; Choi et al, 2013). Engineering PtNi nanocrystals with well-defined shape, phase and composition is the subject of intensive interest to exploit their possible properties and applications (Cao et al, 2017; Zhang et al, 2018)

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