Morphology and Electrochemical Characterization of Electrodeposited Nanocrystalline Ni-Co Electrodes for Methanol Fuel Cells

An electrocatalytic electrode surface was developed for alcoholic fuel cell by electrodeposition of Ni-Co alloy on a 301 stainless steel substrate. Material characterization by EDX and XRD confirmed deposition of Ni-Co alloy on stainless steel surfaces with a cobalt content of 15–35%. SEM showed nodular and/or angular particles with some subparticles embedded within the coarse nodules. Increasing the deposition current density as well as deposition time leads to deposition of Ni-Co alloys characterized by coarse angular morphology with lower cobalt content. The electrocatalytic activity of the coated electrodes was characterized by potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) tests in anodic solution for electrochemical oxidation of methanol. Polarization study showed very much higher current density for the coated electrode compared to bare stainless steel. According to the EIS test in 1 M methyl alcohol acidic solution, it was found that polarization resistance of the coated sample was much lower compared to the bare substrate. The electrical equivalent circuit at the metal solution interface was found to be matching Randle with Warburg resistance. The results of the CV test showed higher peaks for alcohol oxidation and oxygen reduction compared to the bare substrate. The alloy coating with increased effective surface area leads to enhancement in the electrocatalytic activity of the electrodes. The alloys deposited at current densities of 50 and 80 mA/cm2 for 30 minutes (15–16% Co) had higher catalytic activity of the Ni-Co nanocrystalline deposits for methanol oxidation for direct methanol fuel cells, than those under other deposition conditions.