Continuous Synthesis of Highly Uniform Noble Metal Nanoparticles over Reduced Graphene Oxide Using Microreactor Technology

Abstract

Batch reactors always suffer from inefficient transport properties, discontinuity, and scale-up effects, challenging the particle size control, reproducibility, and large-scale production of noble metal-reduced graphene oxide composites. To address these issues, a microfluidic-based strategy for the continuous synthesis of highly uniform Ag nanoparticles (NPs) over reduced graphene oxide (Ag-rGO composites) was developed in this study. Ag-rGO composites were formed by the coreduction of AgNO3 and GO with NaBH4, which was confined inside the dispersed aqueous plugs segmented by octane. By virtue of enhanced mixing and precise control of reaction parameters in the plugs, ultrafine Ag NPs with controlled particle size (1.5–5.6 nm) and narrow particle size distribution (PSD) were evenly deposited on rGO. The average particle size of Ag NPs and relative standard deviation of particle size in Ag-rGO composites synthesized via microfluidic-based strategy were smaller than those via batch method. Moreover, the versatility of this microfluidic-based strategy was further demonstrated in the continuous synthesis of Pt-rGO and Pd-rGO composites.