Platinum-Based Nanowires as Active Catalysts toward Oxygen Reduction Reaction: In Situ Observation of Surface-Diffusion-Assisted, Solid-State Oriented Attachment

Abstract

Facile fabrication of advanced catalysts toward oxygen reduction reaction with improving activity and stability is significant for proton-exchange membrane fuel cells. Based on a generic solid-state reaction, this study reports a modified hydrogen-assisted, gas-phase synthesis for facile, scalable production of surfactant-free, thin, platinum-based nanowire-network electrocatalysts. The free-standing platinum and platinum–nickel alloy nanowires show improvements of up to 5.1 times and 10.9 times for mass activity with a minimum 2.6% loss after an accelerated durability test for 10k cycles; 8.5 times and 13.8 times for specific activity, respectively, compared to commercial Pt/C catalyst. In addition, combined with a wet impregnation method, different substrate-materials-supported platinum-based nanowires are obtained, which paves the way to practical application as a next-generation supported catalyst to replace Pt/C. The growth stages and formation mechanism are investigated by an in situ transmission electron microscopy study. It reveals that the free-standing platinum nanowires form in the solid state via metal-surface-diffusion-assisted oriented attachment of individual nanoparticles, and the interaction with gas molecules plays a critical role, which may represent a gas-molecular-adsorbate-modified growth in catalyst preparation.

Free-standing platinum and platinum–nickel alloy nanowires are synthesized by a modified facile hydrogen-assisted gas-phase method. In situ transmission electron microscopy observation reveals that the formation of nanowires is attributed to surface-diffusion-assisted, solid-state oriented attachment. The Pt and Pt_1.3Ni-alloy nanowires exhibit promising catalytic activity and excellent stability compared with commercial Pt/C toward oxygen reduction reaction.

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