Flow synthesis of Pt and Pt-Ag nanostructures towards hydrogen peroxide electroreduction

Pt nanomaterials exhibit unique catalytic properties. However, the cost of Pt precursors and tedious conventional synthesis strategies limit their applications. In this study, a simple droplet-based in situ synthesis of monometallic and bimetallic Pt nanostructures (NSs) of different morphologies using two different shape-directing agents [polyvinylpyrrolidone (PVP) and silver nitrate (AgNO₃)] by a 3D-printed reactor attached to a heater filament in continuous-flow is demonstrated. Microscopy analysis confirmed that while using PVP, with an increase in temperature and decrease in the flow rate, the morphology of the NS changed from a dendritic/flower structure to a dense ball-like nanomaterial. However, while using AgNO₃ as the shape-directing agent, monodisperse bimetallic Pt-Ag (40% Pt-60% Ag) NSs with spherical morphology were obtained at a high flow rate and high temperature (80 °C) and at a low flow rate and room temperature. The synthesized alloy Pt-Ag NSs showed a distinct redox peak at -0.07 V for hydrogen peroxide electroreduction and improved catalytic behavior with an onset reduction potential at 0.15 V as compared to 0.3 V for monometallic PtNSs.