Flame-based synthesis and in situ functionalization of palladium alloy nanoparticles

Flame-driven synthesis and functionalization of palladium-containing nanoparticles is demonstrated using a high temperature reducing jet (HTRJ) process that decouples flame chemistry from particle formation chemistry and provides a reducing environment that enables synthesis of metal nanoparticles from low-cost aqueous precursors. Nanoparticles with controlled palladium, copper, and silver content were synthesized and functionalized with amine-containing ligands using both in situ and ex situ approaches. For in situ functionalization, octylamine was sprayed into the quench section of the HTRJ reactor to cap the nanoparticles in the gas phase. For the ex situ approach, the “bare” nanopowders were heated in various amines (hexylamine, octylamine, and oleylamine) to form stable dispersions. Use of oleylamine at high temperature allowed modification of the nanoparticle size and shape while maintaining the alloy composition. These in situ and ex situ functionalization methods provide flexibility to tailor particles for specific applications such as electrocatalysis or hydrogen purification.