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

Abstract

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.