Carbon support morphology-dependent in-liquid transfer and formation of RF-sputtered platinum-carbon nanohybrids for electrocatalytic evaluation

We report a surfactant-free, in-liquid approach for the synthesis and transfer of platinum nanoparticles (Pt NPs) produced by radio-frequency (RF) magnetron sputtering directly into poly(ethylene glycol) (PEG). This method yields ultrapure, sub-2 nm Pt NPs and enables their direct liquid-mediated transfer onto carbon supports with two distinct morphologies, namely two-dimensional (2D) graphene sheets and three-dimensional (3D) Vulcan carbon. The approach enables the formation of Pt-carbon nanohybrids while retaining the native nanoscale particle size and dispersion during immobilization, without pronounced aggregation. UV-Vis spectroscopy confirms the formation of stable Pt nanofluids and their efficient transfer to the carbon supports, while transmission electron microscopy (TEM) reveals that support morphology governs nanoparticle distribution and interfacial assembly. Planar graphene sheets promote uniform, high-coverage Pt deposition, whereas Vulcan carbon leads to a more heterogeneous dispersion within its porous network. X-ray photoelectron spectroscopy (XPS) reveals support-dependent electronic interactions, with metallic Pt0 as the dominant Pt species and differences in Pt–support interactions between the two hybrids. Electrocatalytic evaluation of the resulting nanohybrids for the hydrogen evolution reaction (HER) revealed distinct performance trends depending on the normalization basis. Pt–graphene exhibited higher Pt mass-normalized activity, whereas Pt–Vulcan carbon showed more favorable HER kinetics at higher current densities and a larger electrochemically accessible Pt surface area. ECSA-normalized measurements confirmed that the differences in HER response cannot be attributed solely to variations in electrochemically accessible Pt surface area, highlighting the combined influence of carbon-support morphology, catalyst-layer architecture, and Pt-support interactions. These results demonstrate that carbon support morphology plays a key role in liquid-mediated nanoparticle transfer, Pt accessibility, and electrode-level electrocatalytic performance, while the sputtering-in-liquid and in-liquid transfer approach provides a simple, surfactant-free route for fabricating Pt–carbon nanohybrids.