Nanoalloy libraries from laser-induced thermionic emission reduction

Abstract

Nanoalloys, especially high-entropy nanoalloys (HENAs) that contain equal stoichiometric metallic elements in each nanoparticle, are widely used in vast applications. Currently, the synthesis of HENAs is challenged by slow reaction kinetics that leads to phase segregation, sophisticated pretreatment of precursors, and inert conditions that preclude scalable fabrication of HENAs. Here, we report direct conversion of metal salts to ultrafine HENAs on carbonaceous support by nanosecond pulsed laser under atmospheric conditions. Because of the unique laser-induced thermionic emission and etch on carbon, the reduced metal elements were gathered to ultrafine HENAs and stabilized by defective carbon support. This scalable, facile, and low-cost method overcomes the immiscible issue and can produce various HENAs uniformly with a size of 1 to 3 nanometers and metal elements up to 11 with productivity up to 7 grams per hour. One of the senary HENAs exhibited excellent catalytic performance in oxygen reduction reaction, manifesting great potential in practical applications.

Bimetallic Sites for Catalysis: From Binuclear Metal Sites to Bimetallic Nanoclusters and Nanoparticles

“…Another approach to achieve the fast agglomeration of the metal atoms into metastable alloy nanoclusters/nanoclusters is using laser as the energy input source for creating local hot spots in the sample . For instance, the metal ions supported on graphene are reduced by laser propulsion and then the metal–metal bonding are formed, leading to the formation of multimetallic nanoparticles on the graphene support …”

Nanosecond Laser Confined Bismuth Moiety with Tunable Structures on Graphene for Carbon Dioxide Reduction

“…The local temperature could exceed 1500 K upon laser irradiation, which can promote the instant reduction and nucleation of metal cations. 24 The digital images captured the graphene powder movement and the emergence of bright light (Figure 2b) resulting from the thermionic emission induced by laser stimulation. Due to the band structure of graphene, electrons from the valence band were excited to the conduction band when laser pulses were absorbed by graphene, leading to the ejection and liberation of electrons which further drive the reduction of metal cations through Auger-like mechanisms.…”

“…The feasibility of this laser confinement strategy is rooted in the efficient adsorption of the photon energy and conversion to heat by the graphene-based support, allowing for the creation of a transient and localized region with alternating heating and quenching environments as the laser switches on and off. The local temperature could exceed 1500 K upon laser irradiation, which can promote the instant reduction and nucleation of metal cations . The digital images captured the graphene powder movement and the emergence of bright light (Figure b) resulting from the thermionic emission induced by laser stimulation.…”

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…”