Chemistry, Surface Electrochemistry, and Electrocatalysis of Carbon-Supported Palladium-Selenized Nanoparticles

Carbon-supported palladium selenide (PdxSey/C) nanoparticles (NPs) were synthesized as oxygen reduction electrocatalysts for direct methanol fuel cells in an alkaline electrolyte. A simple chemical route of synthesis followed by a heat treatment, in a reducing atmosphere, led to the formation of a chalcogenide shell on carbon-supported palladium NPs used as a precursor. The chalcogenide shell, investigated by X-ray photoelectron spectroscopy, X-ray diffraction, and cyclic voltammetry, consisted of various main components, such as Pd17Se15 and Pd7Se4. The typical finger-print surface reactions of Pd, in acidic and alkaline electrolytes, were suppressed. Applied oxidation electrode potential was identified in both media. These experiments showed that the palladium-selenide material is very stable against oxidation in an acidic medium, moreover less stable in an alkaline medium. Palladium clusters were developed in an alkaline electrolyte and remained stable during the potential interval used. The oxygen reduction reaction (ORR) study, in acidic and alkaline media, on palladium selenide shows that the covalent and noncovalent interactions that the species undergo in the electrolyte play a role in electrocatalysis. The palladium-selenide materials are tolerant to methanol during the ORR as compared to Pd/C. This property was used as a proof-of-concept in a direct methanol microflow fuel cell device.