Controlled Growth of Platinum Nanoparticles during Electrodeposition using Halide Ion Containing Additives

Abstract

Optimizing platinum (Pt) utilization is a necessary step towards developing affordable electrocatalysts for fuel cells and related technologies. Electrodeposition is a scalable approach to preparing Pt nanoparticles (NPs). Herein, Cl− and Br− ions are used in excess as additives during the electrodeposition of Pt NPs to influence nucleation and growth processes as a means of tuning particle morphology and their electrocatalytic activity. Adding NaCl formed larger particles with urchin-like morphologies while adding NaBr produced smaller, more uniform NPs that were evenly dispersed across the substrate. Mixtures of these two halide ion species improved surface coverage and size distribution of the NPs. Particle size was further decreased, and their surface coverage increased by combining the addition of excess halide ions with using a higher applied potential to initiate “nucleation” followed by a lower applied potential to promote particle “growth.” Mass activity towards the oxygen reduction reaction was the highest for Pt NPs electrodeposited in the presence of Br−. The addition of cetyltrimethylammonium chloride and cetyltrimethylammonium bromide during electrodeposition produced small NPs with an even higher mass activity, which was attributed to the formation of porous nanostructures. This study demonstrates techniques to improve Pt utilization and electrocatalytic activity of electrodeposited Pt NPs.