Pd and Pd@PdO core-shell nanoparticles supported on Vulcan carbon XC-72R: comparison of electroactivity for methanol electro-oxidation reaction

Nanomaterials based on Pd nanoparticles supported on Vulcan carbon (XC-72R) were prepared by the organometallic approach in one-pot and mild conditions (3 bar hydrogen and room temperature) using Pd(dba)(2) (bis (dibenzylideneacetone) palladium (0)) as metal source and hexadecylamine (HDA) as stabilizer. High-resolution transmission electron microscopy (HR-TEM) evidenced the presence of well-dispersed Pd nanoparticles of ca. 4.5 nm mean size onto the carbon support (Pd/HDA/C). Scanning and transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) allowed to determine the chemical composition of the nanomaterials. When the Pd/HDA/C nanomaterial was submitted to heating treatment (ht) at 400 degrees C under air (referred as Pd/HDA/C@air-ht), X-ray photoelectron spectroscopy (XPS) and HR-TEM/STEM-EELS analyses suggested the presence of interactions between PdO and Pd(0) as a result of the formation of Pd@PdO core-shell nanoparticles. The highest oxidation current magnitude during methanol oxidation reaction is ascribed to the heat-treated material, linked with a better electron and mass transfer processes at the electrode interface. This can be attributed to electronic interactions at the core-shell formed, which might promote different redox processes at the electrode interface during CH3OH deprotonation in the alkaline electrolyte.