Stable High-Index Faceted Pt Skin on Zigzag-Like PtFe Nanowires Enhances Oxygen Reduction Catalysis

Abstract

Selectively exposing active surfaces and judiciously tuning the near-surface composition of electrode materials represent two prominent means of promoting electrocatalytic performance. Here, a new class of Pt₃Fe zigzag-like nanowires (Pt-skin Pt₃Fe z-NWs) with stable high-index facets (HIFs) and nanosegregated Pt-skin structure is reported, which are capable of substantially boosting electrocatalysis in fuel cells. These unique structural features endow the Pt-skin Pt₃Fe z-NWs with a mass activity of 2.11 A mg⁻¹ and a specifc activity of 4.34 mA cm⁻² for the oxygen reduction reaction (ORR) at 0.9 V versus reversible hydrogen electrode, which are the highest in all reported PtFe-based ORR catalysts. Density function theory calculations reveal a combination of exposed HIFs and formation of Pt-skin structure, leading to an optimal oxygen adsorption energy due to the ligand and strain effects, which is responsible for the much enhanced ORR activities. In contrast to previously reported HIFs-based catalysts, the Pt-skin Pt₃Fe z-NWs maintain ultrahigh durability with little activity decay and negligible structure transformation after 50 000 potential cycles. Overcoming a key technical barrier in electrocatalysis, this work successfully extends the nanosegregated Pt-skin structure to nanocatalysts with HIFs, heralding the exciting prospects of high-effcient Pt-based catalysts in fuel cells.

A unique class of 1D zigzag-like PtFe nanowires is synthesized and further applied as the electrocatalyst toward the oxygen reduction reaction. Extremely high catalytic activity and durability is achieved, highlighting the combination of high-index facets and nanosegregated Pt-skin structure in multimetallic nanocrystals for enhanced electrocatalysis.

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