Preparation of Au@AuAg yolk-shell nanoparticles with porous surface and their catalytic reduction of 4-nitrophenol

Yolk-shell structure nanoparticles, consisting of outer shell, inner core and cavity, are a combination of core-shell structure and hollow structure. Due to the existence of their internal gaps, yolk-shell nanostructures have more excellent optoelectronic properties than hollow nanostructures and core-shell nanostructures, and have promising applications in catalysis, energy storage, drug delivery, lithium batteries, biosensors and nanoreactors. In this paper, gold-silver bimetallic yolk-shell nanoparticles (Au@AuAg Y-SNPs) with porous surface structure were synthesized. The morphology and structure of Au@AuAg Y-SNPs were characterized by UV–vis, XRD, SEM, TEM, HRTEM, SAED, and HAADF-STEM, the results demonstrated that the nanostructures are composed of gold and silver bimetals with various shell thickness, and tunable internal voids. In addition, the catalytic activity of the Au@AuAg yolk-shell nanoparticles were investigated based on the model catalytic reaction of hydrogenation reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with superfluous sodium borohydride. The yolk-shell nanostructure had the best catalytic activity when the ratio of Ag to Au was 1:4. The kinetic constant of the reaction, apparent rate constants (K_app) was 0.0072 s⁻¹ when 100 μL of this nanocatalyst was added. This suggests that Au@AuAg Y-SNPs have a promising application in the removal of pollutants from water bodies and environmental remediation.