Ultrasound-driven fabrication of high-entropy alloy nanocatalysts promoted by alcoholic ionic liquids

High-entropy alloy nanoparticles (HEA-NPs) are highly underutilized in heterogeneous catalysis due to the absence of a reliable, sustainable, and facile synthetic method. Herein, we report a facile synthesis of HEA nanocatalysts realized via an ultrasound-driven wet chemistry method promoted by alcoholic ionic liquids (AILs). Owing to the intrinsic reducing ability of the hydroxyl group, AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process. Under high-intensity ultrasound irradiation, Au3+, Pd2+, Pt2+, Rh3+, and Ru3+ ions were co-reduced and transformed into single-phase HEA (AuPdPtRhRu) nanocrystals without calcination. Characterization results reveal that the as-synthesized nanocrystals are composed of elements of Au, Pd, Pt, Rh, and Ru as expected. Compared to the monometallic counterparts such as Pd-NPs, the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity. Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.

Automated summary

High-entropy alloy nanoparticles (HEA-NPs) are currently underutilized in heterogeneous catalysis due to the lack of a reliable, sustainable, and facile synthetic method. A novel synthesis method utilizing alcoholic ionic liquids (AILs) to promote the formation of HEA nanocatalysts has been developed, resulting in environmentally friendly alternatives to traditional reducing agents and solvents. Ultrasonic irradiation co-reduces and transforms Au3+, Pd2+, Pt2+, Rh3+, and Ru3+ ions into single-phase HEA (AuPdPtRhRu) nanocrystals without the need for calcination, showing superior catalytic performance compared to monometallic counterparts.