A general synthesis approach for amorphous noble metal nanosheets

Geng Wu,Xiaoqian Wang,Xiao Han,Hai Li,Xun Hong,Lin Gu,Yue Lin,Peixin Cui,Peigen Liu,Rongbo Sun,Qinghua Zhang,Jingjie Ge,Yunteng Qu,Wenxing Chen,Xusheng Zheng,Yancai Yao,Yuen Wu,Yanjun Hu ,Hongyu Jiang,Yadong Li

doi:10.1038/s41467-019-12859-2

Abstract

Noble metal nanomaterials have been widely used as catalysts. Common techniques for the synthesis of noble metal often result in crystalline nanostructures. The synthesis of amorphous noble metal nanostructures remains a substantial challenge. We present a general route for preparing dozens of different amorphous noble metal nanosheets with thickness less than 10 nm by directly annealing the mixture of metal acetylacetonate and alkali salts. Tuning atom arrangement of the noble metals enables to optimize their catalytic properties. Amorphous Ir nanosheets exhibit a superior performance for oxygen evolution reaction under acidic media, achieving 2.5-fold, 17.6-fold improvement in mass activity (at 1.53 V vs. reversible hydrogen electrode) over crystalline Ir nanosheets and commercial IrO2 catalyst, respectively. In situ X-ray absorption fine structure spectra indicate the valance state of Ir increased to less than + 4 during the oxygen evolution reaction process and recover to its initial state after the reaction.

Highlights

Noble metal nanomaterials have been widely used as catalysts
Amorphization can efficiently promote the intrinsic properties of Pd3P2S8 for the electrocatalytic hydrogen evolution reaction and amorphous gelled FeCoW oxyhydroxides exhibit a remarkable performance for oxygen evolution reaction (OER) in alkaline electrolyte compared with crystalline counterparts[29,30]
As depicted in X-ray photoelectron spectroscopy (XPS) spectra (Supplementary Fig. 5), the peaks located at 61.0 and 63.9 eV are assigned to Ir (4f7/2) and Ir (4f5/2) of Ir0 and the peaks located at 62.1 and 65.0 eV are assigned to Ir (4f7/2) and Ir (4f5/2) of Ir4+, which can be contributed to partial oxidation of Ir under air atmosphere, respectively[33,34]

Summary

Introduction

Noble metal nanomaterials have been widely used as catalysts. Common techniques for the synthesis of noble metal often result in crystalline nanostructures. Tremendous efforts have been devoted to constructing more active noble metal catalysts by increasing the number of active sites or optimizing the intrinsic activity[7]. To this end, how the size[10], shape[11,12], and crystal phase[13,14,15] of noble nanostructures influence their catalytic performance have been well investigated. The synthesis of amorphous noble metal nanomaterials where elemental composition, material size, and shape can be precisely controlled remains substantial challenges. The obtained amorphous Ir NSs achieve exceptional catalytic activity when benchmarked again commercial catalysts for electrochemical OER under acidic media

Methods

Results

Conclusion