Electrodeposited Pd and PdNi coatings as electrodes for the electrochemical oxidation of ethanol in alkaline media

Abstract

Electrodeposition of Pd and PdNi coating samples of different thicknesses, depending on the coating composition and current efficiency, was achieved galvanostatically on the rotating Au disc electrode from the plating bath containing 0.01 M PdCl2 + 0.6 M NiCl2 + 2 M NH4Cl. Determination of the alloy coating composition was performed by the anodic linear sweep voltammetry (ALSV) analysis, as well as by the energy-dispersive X-ray spectroscopy (EDS). The coating samples were tested for ethanol oxidation reaction (EOR) in alkaline solution using cyclic voltammetry (CV). Among the CVs for the EOR of investigated samples, all alloy samples showed higher current densities for the EOR than pure Pd coating after correction for the electrochemically active surface area (ECSA), actually the roughness factor (Rf). The current density increased with increasing the amount of Pd in the PdNi alloy. The most active one was found to be Pd0.74Ni0.26, with the current density of the forward peak being approximately 1.6, 1.8, and 3 times higher than that for Pd0.50Ni0.50, Pd0.28Ni0.72, and Pd, respectively. Improved catalytic activity of investigated binary coatings was achieved through the optimization of the Ni content and appropriate surface morphology.