Microfluidic continuous flow production of noble bimetallic nanoparticles stabilized on evolvable polymer microspheres for confined synergistic catalysis.

Microspheres with well-defined morphologies have been demonstrated as a promising catalytic carrier to modulate catalytic performance. However, the strategy for controlling the production of such microspheres with noble bimetallic nanoparticles immobilized is limited by complicated procedures and is time-consuming. Here, a facile and robust strategy is developed to prepare polystyrene (PS) microspheres with well-tailored morphology by readily altering the volume ratio of ethanol or toluene to water. Ag monometallic nanoparticles, Ag-Pt, and Ag-Au bimetallic nanoparticles were loaded on the PS matrix via a one-step continuous approach in a spiral microchannel. The hollow and open-hole structure was conducive to loading high content nanoparticles owing to its remarkable surface area, with Ag and Pt loading content are 7% and 10%, respectively. The swell-buckling theory and adsorption-reduction-infiltration mechanism were proposed to explain the PS microsphere's morphology evolution behavior and anchor noble metallic nanoparticles on PS microspheres in a spiral microchannel, respectively. The Ag-Pt@PS and Ag-Au@PS microspheres served as efficient catalysts for the reduction of 4-nitrophenol into 4-aminophenol. The effects of the support morphologies, catalyst amount, and types of noble metal nanoparticles on the catalytic performance were investigated experimentally. The results demonstrated that Ag-Pt@PS and Ag-Au@PS microspheres exhibited much superior catalytic performance than Ag@PS microspheres. More importantly, open-hole PS microspheres loaded with Ag-Pt nanoparticles exhibited the best catalytic performance, with reaction rate constant and activity parameters were 1.73 × 10