Liquid temperature effect on Pt-Sn electrocatalyst properties during plasma sputtering onto polyethylene glycol

Pt-Sn nanoparticles were synthesized by magnetron sputtering of a 2-inch Pt _0.8 Sn _0.2 target into polyethylene glycol using an innovative reactor configuration designed for liquid-phase deposition. A comprehensive study was conducted to understand the influence of liquid temperature on the growth of nanoparticles under two conditions: (i) an in-situ heating of the liquid during sputtering deposition using bain-marie bath, and (ii) an ex-situ post-deposition annealing under air of the nanoparticle-liquid suspension obtained after deposition. COMSOL multiphysics simulations have revealed that the temperature of the liquid critically determines the transport regime of sputtered species inside the liquid glycol thus affecting the nanoparticle formation pathways. Complementary structural and morphological characterisations, such as transmission electron microscopy, X-ray diffraction and small angle X-ray scattering, demonstrate that temperature modulates particle size and size distribution. The in-situ heating of the liquid during the growth promotes aggregation and the emergence of interparticle correlations but do not significantly modify the size distribution of the NPs. The ex-situ annealing treatment up to 150°C of the as-deposited NPs affects their organization in solution, lightly alter their intrinsic size and can induce structural and microstructural modifications of the NPs and particularly affect the elemental distribution of Pt and Sn. These results provide new insights into temperature-controlled synthesis of alloy nanoparticles in liquids.