Oxygen Electroreduction in Alkaline Solution on Pd Coatings Prepared by Galvanic Exchange of Copper

Abstract

Thin Pd coatings were obtained on glassy carbon electrodes by galvanically replacing the electron beam-deposited copper layers with palladium. The prepared electrodes were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The electrodes were electrochemically tested for oxygen reduction reaction (ORR) employing the rotating disc electrode (RDE) method in alkaline solution. The remaining copper was detected for two of the thickest (5 and 10 nm) sacrificial Cu layers using energy-dispersive X-ray spectroscopy (EDX). SEM images of thin Pd films showed some larger particle growth for all the studied film thicknesses, but spherical particles such as those achieved for example by the electron beam evaporation method were not visible. Specific activity of the electrodes for O2 reduction did not depend on the thickness of the sacrificial copper layer. The O2 reduction reaction followed a four-electron pathway with a mechanism similar to that of commercial Pd/C, where the first electron transfer to the O2 molecule is the rate-determining step.