Noble-Metal High-Entropy-Alloy Nanoparticles: Atomic-Level Insight into the Electronic Structure

Abstract

The compositional space of high-entropy-alloy nanoparticles (HEA NPs) significantly expands the diversity of the materials library. Every atom in HEA NPs has a different elemental coordination environment, which requires knowledge of the local electronic structure at an atomic level. However, such structure has not been disclosed experimentally or theoretically. We synthesized HEA NPs composed of all eight noble-metal-group elements (NM-HEA) for the first time. Their electronic structure was revealed by hard X-ray photoelectron spectroscopy and density function theory calculations with NP models. The NM-HEA NPs have a lower degeneracy in energy level compared with the monometallic NPs, which is a common feature of HEA NPs. The local density of states (LDOS) of every surface atom was first revealed. Some atoms of the same constituent element in HEA NPs have different LDOS profiles, whereas atoms of other elements have similar LDOS profiles. In other words, one atom in HEA loses its elemental identity and it may be possible to create an ideal LDOS by adjusting the neighboring atoms. The tendency of the electronic structure change was shown by supervised learning. The NM-HEA NPs showed 10.8-times higher intrinsic activity for hydrogen evolution reaction than commercial Pt/C, which is one of the best catalysts.

Cast Microstructure of a Complex Concentrated Noble Alloy Ag20Pd20Pt20Cu20Ni20

“…Table 4. Field lattice parameters obtained by XRD analysis and calculated analysis (Vegard's law) [13].…”

“…Previous research in the field of noble HEAs represents relatively new findings in the field of science. Only a couple of scientific papers [ 13 , 14 , 15 , 16 ] have been observed in the literature, which mainly deal with a single—phase PdPtRhIrCuNi type of alloy. In these papers, the rules for the formation of the SS phase [ 16 ], the development of nanoparticles of this type [ 13 ], the assumptions of mechanical properties [ 15 ], as well as the electrocatalytic use [ 17 ], are presented.…”

Surface‐Decorated High‐Entropy Alloy Catalysts with Significantly Boosted Activity and Stability

“…[ 1–6 ] The use of multiple elements significantly broadens the compositional space and affords tunable microstructures to achieve high performance. It is reported that HEA catalysts are featured with complex atomic configurations and diverse adsorption sites, which result in a near‐continuous distribution in binding energy [ 7–9 ] that is well‐suited for multi‐step reactions having a wide range of intermediates. [ 10 ] Meanwhile, the high‐entropy structure usually leads to the excellent structural stability of HEA catalysts, either through the thermodynamic entropy stabilization effect or kinetic sluggish diffusion, [ 11–20 ] thus promoting their applications in harsh environments.…”

Ab Initio to activity: Machine learning assisted optimization of high-entropy alloy catalytic activity.

“…High-entropy alloys (HEAs) and complex solid solutions hold great potential for catalyst discovery [1][2][3][4][5][6][7] because the metal surfaces can be tuned to maximize the likelihood of ideal binding sites for specific reactions in accordance with the Sabatier principle [8]. However, the huge composition space available to these materials presents a challenge to any rational discovery procedure, as the selection of constituent elements and ratios makes experimental screening virtually impossible.…”