Synergy of Pt, Rh and SnO₂ nanoparticles supported on carbon: Influence of microstructures on the selectivity of ethanol oxidation

This study investigates the physicochemical and electrochemical properties of carbon-supported Pt, Pt-Sn, Pt-Rh, and Pt-Sn-Rh nanoparticles for ethanol oxidation reaction (EOR). X-ray diffraction (XRD) analysis reveals the face-centered cubic crystal structure of Pt. Transmission electron microscopy (TEM) images show well-dispersed nanoparticles on carbon support, with Pt-Sn-Rh exhibiting an average particle size of 2.8 ± 0.2 nm. High-resolution TEM and energy-dispersive X-ray (EDX) microanalysis confirm the presence of SnO₂, Pt-Rh, and Pt-Sn. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of metallic Pt along with SnO₂ in the Pt-Sn-Rh/C catalyst. Chronoamperometry combined with accelerated degradation tests (ADTs) demonstrates the excellent catalytic stability of Pt-Sn-Rh/C. CO stripping voltammetry also shows that the incorporation of Sn and Rh into Pt facilitates CO oxidation at low potentials. Pt-Sn-Rh/C excels at low ethanol concentrations due to the Eley-Rideal mechanism, whereas Pt-Sn/C performs better at high concentrations owing to SnO₂-rich surfaces favoring the Langmuir-Hinshelwood pathway.