Methanol electro-oxidation on a porous nanostructured Ni/Pd-Ni electrode in alkaline media

Abstract

A nanostructured Ni/Pd-Ni catalyst with high activity for methanol oxidation in alkaline solution was prepared by electrodeposition followed by galvanic replacement, that is, electrodeposition of Ni-Zn on a Ni coating with subsequent replacement of the Zn by Pd at the open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of the coatings were examined by energy dispersive X-ray spectroscopy and scanning electron microscopy. The Ni/Pd-Ni coatings were porous and were composed of discrete Pd nanoparticles of about 58 nm. The electrocatalytic activity of the Ni/Pd-Ni electrodes for the oxidation of methanol was examined by cyclic voltammetry and electrochemical impedance spectroscopy. The onset potentials for methanol oxidation on Ni/Pd-Ni were 0.077 V and 0.884 V, which were lower than those for flat Pd and smooth Ni electrodes, respectively. The anodic peak current densities of these electrodes were 4.33 and 8.34 times higher than those of flat Pd (58.4 mA/cm 2 vs 13.47 mA/cm 2 ) and smooth Ni (58.4 mA/cm 2 vs 7 mA/cm 2 ). The nanostructured Ni/Pd-Ni electrode is a promising catalyst for methanol oxidation in alkaline media for fuel cell application. The nanostructured Ni/Pd-Ni electrode shows significantly greater electro-catalytic activity towards methanol oxidation than flat palladium and smooth nickel electrodes. The high activity of Ni/Pd-Ni electrode can be attributed to its high surface area.