Improved ethanol electrooxidation performance by shortening Pd\u2013Ni active site distance in Pd\u2013Ni\u2013P nanocatalysts

Yueguang Chen,Yu Huang,Lin Chen,Lilin Lu,Leyu Wang,Hengli Zhu,Yadong Li

doi:10.1038/ncomms14136

Abstract

Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (∼5 nm) Pd–Ni–P ternary nanoparticles for ethanol electrooxidation. The activity is improved up to 4.95 A per mgPd, which is 6.88 times higher than commercial Pd/C (0.72 A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni–P heterodimers into Pd–Ni–P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites.

Highlights

Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells
Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites
According to the clear lattice fringes shown in the high-resolution TEM (HRTEM) image, the Pd species still existed as large domains in the Ni–P matrixes (Fig. 2e and Supplementary Fig. 2b)

Summary

Introduction

Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. The activity is improved up to 4.95 A per mgPd, which is 6.88 times higher than commercial Pd/C (0.72 A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni–P heterodimers into Pd–Ni–P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. The controlled synthesis of ultrasmall Pd–Ni–P ternary NPs with rich and adjacent Pd and Ni active sites is still challenging but highly attractive to increase the EOR catalytic performance. We report a two-step solvothermal strategy for the synthesis of small (B5 nm) Pd–Ni–P ternary NPs with tunable Ni/Pd atomic ratio and controlled distance between Pd and Ni active sites (termed as Pd–Ni distance). The EOR activity is substantially enhanced from 4.12 to 4.42 A per mgPd and 4.95 A per mgPd, which are 5.72, 6.14 and 6.88 times compared with that of commercial Pd/C (0.72 A per mgPd), respectively

Methods

Results

Conclusion