On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles.

Dongshuang Wu,Tomokazu Yamamoto,Hiroshi Kitagawa,Takaaki Toriyama,Jaemyung Kim,Shogo Kawaguchi,Ibrahima Gueye,Okkyun Seo,Satoshi Hiroi,Kohei Kusada,Osami Sakata,Yoshiki Kubota,Syo Matsumura

doi:10.1039/d0sc02351e

Abstract

We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.

Highlights

High-entropy alloys (HEAs) are solid solutions consisting of at least ve elements in an approximately equal atomic ratio.[1]
We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs
We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy (HAXPES), which is the rst direct observation of the electronic structure of HEA NPs

Summary

Introduction

High-entropy alloys (HEAs) are solid solutions consisting of at least ve elements in an approximately equal atomic ratio (recently extended to 5 to 35 at%).[1]. Dongshuang Wu, *a Kohei Kusada, *a Tomokazu Yamamoto,b Takaaki Toriyama,c Syo Matsumura,bc Ibrahima Gueye,d Okkyun Seo,d Jaemyung Kim,d Satoshi Hiroi,d Osami Sakata, de Shogo Kawaguchi,f Yoshiki Kubotag and Hiroshi Kitagawa *a

Results

Conclusion