A General Synthetic Method for High-Entropy Alloy Subnanometer Ribbons

Abstract

High-entropy alloys (HEAs) are attracting intensive attention due to their broad compositional tunability and interesting catalytic properties. However, precisely shaping the HEAs into suprathin low-dimensional nanostructures for achieving diverse applications remains an enormous challenge owing to their intrinsic thermodynamic instability. Herein we propose a new and general low-temperature method for incorporating up to eight metallic elements into one single-phase subnanometer ribbon to achieve the thinnest HEA metal materials in the world. We experimentally demonstrate that synthetic processes for suprathin HEA subnanometer ribbons (SNRs) include (1) different metal atom nucleation via galvanic exchange reaction between different metal precursors and Ag nanowire template, (2) co-reduction of different metal precursors on nanowire template, and (3) the removal of the inner Ag core. Density functional theory (DFT) calculations reveal that the crystallization and stabilization of HEA SNRs strongly depend on the “highly dynamic” Ag from the template, and the crystallization levels of HEA subnanometer ribbons are closely correlated with the concentration of Pt and Pd. We demonstrate that the present synthetic method enables the flexible control of components and concentrations in HEAs SNRs for achieving a library of HEA SNRs and also superior electrocatalytic properties. The well-designed HEA SNRs show great improvement in catalyzing the oxygen reduction reaction of fuel cells and also high discharge capacity, low charge overpotential, and excellent durability for Li–O2 batteries. DFT calculations reveal the superior electrochemical performances are attributed to the strong reduction capability from high-concentration reductive elements in HEAs, while the other elements guarantee the site-to-site efficient electron transfer.

Quinary, Senary, and Septenary High Entropy Alloy Nanoparticle Catalysts from Core@Shell Nanoparticles and the Significance of Intraparticle Heterogeneity

“…For example, McCormick et al demonstrated a multication exchange method to synthesize high-entropy metal sulfide NPs (ZnCoCuInGaS) from roxbyte CuS NPs . Tao et al reported HEA nanoribbons by coupling galvanic replacement of Ag nanowires with co-reduction, and our group demonstrated thermal conversion of colloidally prepared core@shell NPs to HEA NPs . Considering the latter, core@shell PdCu@PtNiCo NPs were prepared by seed-mediated co-reduction (SMCR).…”

Strain-Regulated Pd/Cu Core/Shell Icosahedra for Tunable Syngas Electrosynthesis from CO2

“…Cu(COOH) 2 was then reduced and precipitated on Pd ico seeds, resulting in the formation of Pd/Cu core/shell ico. 29 The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and TEM were first employed to investigate the morphology and structure of Pd/Cu core/shell ico (feed ratio of Pd and Cu = 2.5:1). The Pd/Cu ico are fairly uniform in terms of size without any irregular nanoparticles (Figure S1b).…”

“…Then, Pd ico were dispersed in EG to mix with Cu­(COOH) 2 and ascorbic acid (AA). Cu­(COOH) 2 was then reduced and precipitated on Pd ico seeds, resulting in the formation of Pd/Cu core/shell ico . The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and TEM were first employed to investigate the morphology and structure of Pd/Cu core/shell ico (feed ratio of Pd and Cu = 2.5:1).…”

High-entropy-alloy nanoparticles synthesized by laser metallurgy using a multivariate MOF

“…Typically, materials are regarded as high-entropy-alloy nanoparticles (HEANPs) when the number of metal components goes beyond 5. [6][7][8][9][10][11][12][13] The formation of a high entropy compound usually involves a kinetically controlled process, with stringent requirement on the precursor and temperature. 14,15 Metal-organic frameworks (MOFs) are porous crystals constructed by alternating arrangement of metal clusters and organic linkers, 16,17 standing as ideal precursors with atomic precision of the metal distribution.…”

“…Typically, materials are regarded as high-entropy-alloy nanoparticles (HEANPs) when the number of metal components goes beyond 5. 6–13 The formation of a high entropy compound usually involves a kinetically controlled process, with stringent requirement on the precursor and temperature. 14,15…”