Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction.

Deli Wang,Jie Wang,Héctor D Abruña,Michael A Lowe,Dennis Nordlund,Huolin L Xin,Katharine E Silberstein,Sufen Liu,Ruoqian Lin,David A Muller,Feng Lin,Masahiro Kawasaki,Eric Rus,Hongfang Liu

doi:10.1038/ncomms11941

Abstract

Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.

Highlights

Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts
Pd6CoCu nanoparticles supported on Vulcan XC-72 carbon (Pd6CoCu/C) were synthesized using an impregnation reduction method followed by high temperature heat-treatment as reported previously[8,14,30]
The surface composition of the particles was determined by X-ray photoelectron spectroscopy (XPS) (Supplementary Fig. 2)

Summary

Introduction

Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. Numerous strategies have been employed including developing new structures and morphologies for Pt-based nanocatalysts[3,8,9,10,11,12,13], Pt monolayer decorated nanoparticles[14,15], other platinum group nanomaterials[16,17,18,19], as well as non-precious-metal nanoparticles[16,20,21,22,23,24] Among these alternatives, Pd is very attractive because it is much more abundant and less expensive than Pt. the ORR activity of pure Pd in acid is much lower than that of Pt. Previous studies have focused on alloying Pd with 3d transition metals, such as Fe25, Co14, Ni26, Cu27 and others, resulting in a significant improvement in catalytic activity. We show that Au atoms can penetrate the bulk lattice of Pd6CoCu nanoparticles and spontaneously replace Co and Cu atoms in the interior of the nanoparticles through galvanic replacement reactions This effect allows the uniform incorporation of trace amounts of Au in Pd6CoCu nanoparticles, which enhances the long-term stability of the electrocatalyst for the ORR. PEMFC single-cell performance using a Au–Pd6CoCu/C cathode electrocatalyst exhibits a maximum power-density loss of about 21% after a 100-h stress test at 80 °C, which is dramatically better than a Au-free catalyst

Methods

Results

Conclusion