Microfluidic continuous flow production of noble bimetallic nanoparticles stabilized on evolvable polymer...

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^-2s^-1 and 692 s^-1·g^-1, whereas without sacrificing catalytic activity even after five cycle reusability. The results not only provide an efficient continuous strategy for bimetallic catalysts preparation but also offer an effective strategy to regulate the noble metal nanoparticles via the support structure modulation for confined synergistic catalysis.