Ordering‐Dependent Hydrogen Evolution and Oxygen Reduction Electrocatalysis of High‐Entropy Intermetallic Pt₄FeCoCuNi

Abstract

Disordered solid‐solution high‐entropy alloys have attracted wide research attention as robust electrocatalysts. In comparison, ordered high‐entropy intermetallics have been hardly explored and the effects of the degree of chemical ordering on catalytic activity remain unknown. In this study, a series of multicomponent intermetallic Pt4FeCoCuNi nanoparticles with tunable ordering degrees is fabricated. The transformation mechanism of the multicomponent nanoparticles from disordered structure into ordered structure is revealed at the single‐particle level, and it agrees with macroscopic analysis by selected‐area electron diffraction and X‐ray diffraction. The electrocatalytic performance of Pt4FeCoCuNi nanoparticles correlates well with their crystal structure and electronic structure. It is found that increasing the degree of ordering promotes electrocatalytic performance. The highly ordered Pt4FeCoCuNi achieves the highest mass activities toward both acidic oxygen reduction reaction (ORR) and alkaline hydrogen evolution reaction (HER) which are 18.9‐fold and 5.6‐fold higher than those of commercial Pt/C, respectively. The experiment also shows that this catalyst demonstrates better long‐term stability than both partially ordered and disordered Pt4FeCoCuNi as well as Pt/C when subject to both HER and ORR. This ordering‐dependent structure–property relationship provides insight into the rational design of catalysts and stimulates the exploration of many other multicomponent intermetallic alloys.

Optimization strategies of high-entropy alloys for electrocatalytic applications

“…For example, Ni, Co, Fe and Pt are often used to prepare highly active bifunctional HEAs for the HER and OER. 15,125,126 The coordination between multiple metals is beneficial to optimize the electron density and adjust the adsorption strength, usually exhibiting higher performance than single-component metals.…”

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

“…High-entropy alloys can be macroscopically defined as a novel material containing five or more dominant elemental components, of which the atomic percentage of constituent elements varying from 5% to 35%. − Due to the four-core effect, including high-entropy effect, lattice distortion effect, sluggish diffusion effect, and cocktail effect, high-entropy alloys have been widely applied in the field of biomedical materials, aerospace engineering, photothermal conversion, building materials, and magnetocaloric response, etc. − Especially, the continuous adjustment of the surface electronic structure on high-entropy alloys in nanoscale stimulates the development of heterogeneous catalysis. − High-entropy intermetallics, as a brand new concept, can integrate the advantages of high-entropy alloys and intermetallics, thus becoming an important supplement to high-entropy alloys and intermetallics and further enhancing the electrocatalytic activity and stability (Scheme a). − Although the ordered structure is an important feature of intermetallics different from disordered solid-solution alloys, the site occupancy in each sublattice of high-entropy intermetallics is still random or nearly random due to the more constituent elements than sublattices (Figure a).…”

Proton Relay for the Rate Enhancement of Electrochemical Hydrogen Reactions at Heterogeneous Interfaces

“…Conventional design of heterogeneous electrocatalysts has focused on modifying the catalyst surface electronic structure through alloying, − crystalline structuring, and atomic ordering and orientation , to tune the covalent interactions of surfaces with reaction intermediates (e.g., surface binding or adsorption). − These approaches have led to significant progress in improving catalyst activity for a variety of electrocatalytic reactions, including the hydrogen evolution and oxidation reaction (HER/HOR), , the oxygen evolution and reduction reaction (OER/ORR), , CO 2 reduction reactions (CO 2 RR), , etc. In nature, the kinetics of these reactions are governed not only through covalent interactions but also through noncovalent interactions, the most important of which is tuning proton transfer near the catalyst surface. − …”